| 1 | /* |
| 2 | * Read-Copy Update mechanism for mutual exclusion |
| 3 | * |
| 4 | * This program is free software; you can redistribute it and/or modify |
| 5 | * it under the terms of the GNU General Public License as published by |
| 6 | * the Free Software Foundation; either version 2 of the License, or |
| 7 | * (at your option) any later version. |
| 8 | * |
| 9 | * This program is distributed in the hope that it will be useful, |
| 10 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 11 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 12 | * GNU General Public License for more details. |
| 13 | * |
| 14 | * You should have received a copy of the GNU General Public License |
| 15 | * along with this program; if not, write to the Free Software |
| 16 | * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 17 | * |
| 18 | * Copyright IBM Corporation, 2008 |
| 19 | * |
| 20 | * Authors: Dipankar Sarma <dipankar@in.ibm.com> |
| 21 | * Manfred Spraul <manfred@colorfullife.com> |
| 22 | * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version |
| 23 | * |
| 24 | * Based on the original work by Paul McKenney <paulmck@us.ibm.com> |
| 25 | * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. |
| 26 | * |
| 27 | * For detailed explanation of Read-Copy Update mechanism see - |
| 28 | * Documentation/RCU |
| 29 | */ |
| 30 | #include <linux/types.h> |
| 31 | #include <linux/kernel.h> |
| 32 | #include <linux/init.h> |
| 33 | #include <linux/spinlock.h> |
| 34 | #include <linux/smp.h> |
| 35 | #include <linux/rcupdate.h> |
| 36 | #include <linux/interrupt.h> |
| 37 | #include <linux/sched.h> |
| 38 | #include <linux/nmi.h> |
| 39 | #include <asm/atomic.h> |
| 40 | #include <linux/bitops.h> |
| 41 | #include <linux/module.h> |
| 42 | #include <linux/completion.h> |
| 43 | #include <linux/moduleparam.h> |
| 44 | #include <linux/percpu.h> |
| 45 | #include <linux/notifier.h> |
| 46 | #include <linux/cpu.h> |
| 47 | #include <linux/mutex.h> |
| 48 | #include <linux/time.h> |
| 49 | |
| 50 | #include "rcutree.h" |
| 51 | |
| 52 | /* Data structures. */ |
| 53 | |
| 54 | static struct lock_class_key rcu_node_class[NUM_RCU_LVLS]; |
| 55 | |
| 56 | #define RCU_STATE_INITIALIZER(name) { \ |
| 57 | .level = { &name.node[0] }, \ |
| 58 | .levelcnt = { \ |
| 59 | NUM_RCU_LVL_0, /* root of hierarchy. */ \ |
| 60 | NUM_RCU_LVL_1, \ |
| 61 | NUM_RCU_LVL_2, \ |
| 62 | NUM_RCU_LVL_3, \ |
| 63 | NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \ |
| 64 | }, \ |
| 65 | .signaled = RCU_GP_IDLE, \ |
| 66 | .gpnum = -300, \ |
| 67 | .completed = -300, \ |
| 68 | .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&name.onofflock), \ |
| 69 | .orphan_cbs_list = NULL, \ |
| 70 | .orphan_cbs_tail = &name.orphan_cbs_list, \ |
| 71 | .orphan_qlen = 0, \ |
| 72 | .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&name.fqslock), \ |
| 73 | .n_force_qs = 0, \ |
| 74 | .n_force_qs_ngp = 0, \ |
| 75 | } |
| 76 | |
| 77 | struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state); |
| 78 | DEFINE_PER_CPU(struct rcu_data, rcu_sched_data); |
| 79 | |
| 80 | struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state); |
| 81 | DEFINE_PER_CPU(struct rcu_data, rcu_bh_data); |
| 82 | |
| 83 | /* |
| 84 | * Return true if an RCU grace period is in progress. The ACCESS_ONCE()s |
| 85 | * permit this function to be invoked without holding the root rcu_node |
| 86 | * structure's ->lock, but of course results can be subject to change. |
| 87 | */ |
| 88 | static int rcu_gp_in_progress(struct rcu_state *rsp) |
| 89 | { |
| 90 | return ACCESS_ONCE(rsp->completed) != ACCESS_ONCE(rsp->gpnum); |
| 91 | } |
| 92 | |
| 93 | /* |
| 94 | * Note a quiescent state. Because we do not need to know |
| 95 | * how many quiescent states passed, just if there was at least |
| 96 | * one since the start of the grace period, this just sets a flag. |
| 97 | */ |
| 98 | void rcu_sched_qs(int cpu) |
| 99 | { |
| 100 | struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu); |
| 101 | |
| 102 | rdp->passed_quiesc_completed = rdp->gpnum - 1; |
| 103 | barrier(); |
| 104 | rdp->passed_quiesc = 1; |
| 105 | } |
| 106 | |
| 107 | void rcu_bh_qs(int cpu) |
| 108 | { |
| 109 | struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu); |
| 110 | |
| 111 | rdp->passed_quiesc_completed = rdp->gpnum - 1; |
| 112 | barrier(); |
| 113 | rdp->passed_quiesc = 1; |
| 114 | } |
| 115 | |
| 116 | /* |
| 117 | * Note a context switch. This is a quiescent state for RCU-sched, |
| 118 | * and requires special handling for preemptible RCU. |
| 119 | */ |
| 120 | void rcu_note_context_switch(int cpu) |
| 121 | { |
| 122 | rcu_sched_qs(cpu); |
| 123 | rcu_preempt_note_context_switch(cpu); |
| 124 | } |
| 125 | |
| 126 | #ifdef CONFIG_NO_HZ |
| 127 | DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = { |
| 128 | .dynticks_nesting = 1, |
| 129 | .dynticks = 1, |
| 130 | }; |
| 131 | #endif /* #ifdef CONFIG_NO_HZ */ |
| 132 | |
| 133 | static int blimit = 10; /* Maximum callbacks per softirq. */ |
| 134 | static int qhimark = 10000; /* If this many pending, ignore blimit. */ |
| 135 | static int qlowmark = 100; /* Once only this many pending, use blimit. */ |
| 136 | |
| 137 | module_param(blimit, int, 0); |
| 138 | module_param(qhimark, int, 0); |
| 139 | module_param(qlowmark, int, 0); |
| 140 | |
| 141 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed); |
| 142 | static int rcu_pending(int cpu); |
| 143 | |
| 144 | /* |
| 145 | * Return the number of RCU-sched batches processed thus far for debug & stats. |
| 146 | */ |
| 147 | long rcu_batches_completed_sched(void) |
| 148 | { |
| 149 | return rcu_sched_state.completed; |
| 150 | } |
| 151 | EXPORT_SYMBOL_GPL(rcu_batches_completed_sched); |
| 152 | |
| 153 | /* |
| 154 | * Return the number of RCU BH batches processed thus far for debug & stats. |
| 155 | */ |
| 156 | long rcu_batches_completed_bh(void) |
| 157 | { |
| 158 | return rcu_bh_state.completed; |
| 159 | } |
| 160 | EXPORT_SYMBOL_GPL(rcu_batches_completed_bh); |
| 161 | |
| 162 | /* |
| 163 | * Force a quiescent state for RCU BH. |
| 164 | */ |
| 165 | void rcu_bh_force_quiescent_state(void) |
| 166 | { |
| 167 | force_quiescent_state(&rcu_bh_state, 0); |
| 168 | } |
| 169 | EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state); |
| 170 | |
| 171 | /* |
| 172 | * Force a quiescent state for RCU-sched. |
| 173 | */ |
| 174 | void rcu_sched_force_quiescent_state(void) |
| 175 | { |
| 176 | force_quiescent_state(&rcu_sched_state, 0); |
| 177 | } |
| 178 | EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state); |
| 179 | |
| 180 | /* |
| 181 | * Does the CPU have callbacks ready to be invoked? |
| 182 | */ |
| 183 | static int |
| 184 | cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp) |
| 185 | { |
| 186 | return &rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]; |
| 187 | } |
| 188 | |
| 189 | /* |
| 190 | * Does the current CPU require a yet-as-unscheduled grace period? |
| 191 | */ |
| 192 | static int |
| 193 | cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp) |
| 194 | { |
| 195 | return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp); |
| 196 | } |
| 197 | |
| 198 | /* |
| 199 | * Return the root node of the specified rcu_state structure. |
| 200 | */ |
| 201 | static struct rcu_node *rcu_get_root(struct rcu_state *rsp) |
| 202 | { |
| 203 | return &rsp->node[0]; |
| 204 | } |
| 205 | |
| 206 | #ifdef CONFIG_SMP |
| 207 | |
| 208 | /* |
| 209 | * If the specified CPU is offline, tell the caller that it is in |
| 210 | * a quiescent state. Otherwise, whack it with a reschedule IPI. |
| 211 | * Grace periods can end up waiting on an offline CPU when that |
| 212 | * CPU is in the process of coming online -- it will be added to the |
| 213 | * rcu_node bitmasks before it actually makes it online. The same thing |
| 214 | * can happen while a CPU is in the process of coming online. Because this |
| 215 | * race is quite rare, we check for it after detecting that the grace |
| 216 | * period has been delayed rather than checking each and every CPU |
| 217 | * each and every time we start a new grace period. |
| 218 | */ |
| 219 | static int rcu_implicit_offline_qs(struct rcu_data *rdp) |
| 220 | { |
| 221 | /* |
| 222 | * If the CPU is offline, it is in a quiescent state. We can |
| 223 | * trust its state not to change because interrupts are disabled. |
| 224 | */ |
| 225 | if (cpu_is_offline(rdp->cpu)) { |
| 226 | rdp->offline_fqs++; |
| 227 | return 1; |
| 228 | } |
| 229 | |
| 230 | /* If preemptable RCU, no point in sending reschedule IPI. */ |
| 231 | if (rdp->preemptable) |
| 232 | return 0; |
| 233 | |
| 234 | /* The CPU is online, so send it a reschedule IPI. */ |
| 235 | if (rdp->cpu != smp_processor_id()) |
| 236 | smp_send_reschedule(rdp->cpu); |
| 237 | else |
| 238 | set_need_resched(); |
| 239 | rdp->resched_ipi++; |
| 240 | return 0; |
| 241 | } |
| 242 | |
| 243 | #endif /* #ifdef CONFIG_SMP */ |
| 244 | |
| 245 | #ifdef CONFIG_NO_HZ |
| 246 | |
| 247 | /** |
| 248 | * rcu_enter_nohz - inform RCU that current CPU is entering nohz |
| 249 | * |
| 250 | * Enter nohz mode, in other words, -leave- the mode in which RCU |
| 251 | * read-side critical sections can occur. (Though RCU read-side |
| 252 | * critical sections can occur in irq handlers in nohz mode, a possibility |
| 253 | * handled by rcu_irq_enter() and rcu_irq_exit()). |
| 254 | */ |
| 255 | void rcu_enter_nohz(void) |
| 256 | { |
| 257 | unsigned long flags; |
| 258 | struct rcu_dynticks *rdtp; |
| 259 | |
| 260 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ |
| 261 | local_irq_save(flags); |
| 262 | rdtp = &__get_cpu_var(rcu_dynticks); |
| 263 | rdtp->dynticks++; |
| 264 | rdtp->dynticks_nesting--; |
| 265 | WARN_ON_ONCE(rdtp->dynticks & 0x1); |
| 266 | local_irq_restore(flags); |
| 267 | } |
| 268 | |
| 269 | /* |
| 270 | * rcu_exit_nohz - inform RCU that current CPU is leaving nohz |
| 271 | * |
| 272 | * Exit nohz mode, in other words, -enter- the mode in which RCU |
| 273 | * read-side critical sections normally occur. |
| 274 | */ |
| 275 | void rcu_exit_nohz(void) |
| 276 | { |
| 277 | unsigned long flags; |
| 278 | struct rcu_dynticks *rdtp; |
| 279 | |
| 280 | local_irq_save(flags); |
| 281 | rdtp = &__get_cpu_var(rcu_dynticks); |
| 282 | rdtp->dynticks++; |
| 283 | rdtp->dynticks_nesting++; |
| 284 | WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); |
| 285 | local_irq_restore(flags); |
| 286 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
| 287 | } |
| 288 | |
| 289 | /** |
| 290 | * rcu_nmi_enter - inform RCU of entry to NMI context |
| 291 | * |
| 292 | * If the CPU was idle with dynamic ticks active, and there is no |
| 293 | * irq handler running, this updates rdtp->dynticks_nmi to let the |
| 294 | * RCU grace-period handling know that the CPU is active. |
| 295 | */ |
| 296 | void rcu_nmi_enter(void) |
| 297 | { |
| 298 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
| 299 | |
| 300 | if (rdtp->dynticks & 0x1) |
| 301 | return; |
| 302 | rdtp->dynticks_nmi++; |
| 303 | WARN_ON_ONCE(!(rdtp->dynticks_nmi & 0x1)); |
| 304 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
| 305 | } |
| 306 | |
| 307 | /** |
| 308 | * rcu_nmi_exit - inform RCU of exit from NMI context |
| 309 | * |
| 310 | * If the CPU was idle with dynamic ticks active, and there is no |
| 311 | * irq handler running, this updates rdtp->dynticks_nmi to let the |
| 312 | * RCU grace-period handling know that the CPU is no longer active. |
| 313 | */ |
| 314 | void rcu_nmi_exit(void) |
| 315 | { |
| 316 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
| 317 | |
| 318 | if (rdtp->dynticks & 0x1) |
| 319 | return; |
| 320 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ |
| 321 | rdtp->dynticks_nmi++; |
| 322 | WARN_ON_ONCE(rdtp->dynticks_nmi & 0x1); |
| 323 | } |
| 324 | |
| 325 | /** |
| 326 | * rcu_irq_enter - inform RCU of entry to hard irq context |
| 327 | * |
| 328 | * If the CPU was idle with dynamic ticks active, this updates the |
| 329 | * rdtp->dynticks to let the RCU handling know that the CPU is active. |
| 330 | */ |
| 331 | void rcu_irq_enter(void) |
| 332 | { |
| 333 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
| 334 | |
| 335 | if (rdtp->dynticks_nesting++) |
| 336 | return; |
| 337 | rdtp->dynticks++; |
| 338 | WARN_ON_ONCE(!(rdtp->dynticks & 0x1)); |
| 339 | smp_mb(); /* CPUs seeing ++ must see later RCU read-side crit sects */ |
| 340 | } |
| 341 | |
| 342 | /** |
| 343 | * rcu_irq_exit - inform RCU of exit from hard irq context |
| 344 | * |
| 345 | * If the CPU was idle with dynamic ticks active, update the rdp->dynticks |
| 346 | * to put let the RCU handling be aware that the CPU is going back to idle |
| 347 | * with no ticks. |
| 348 | */ |
| 349 | void rcu_irq_exit(void) |
| 350 | { |
| 351 | struct rcu_dynticks *rdtp = &__get_cpu_var(rcu_dynticks); |
| 352 | |
| 353 | if (--rdtp->dynticks_nesting) |
| 354 | return; |
| 355 | smp_mb(); /* CPUs seeing ++ must see prior RCU read-side crit sects */ |
| 356 | rdtp->dynticks++; |
| 357 | WARN_ON_ONCE(rdtp->dynticks & 0x1); |
| 358 | |
| 359 | /* If the interrupt queued a callback, get out of dyntick mode. */ |
| 360 | if (__get_cpu_var(rcu_sched_data).nxtlist || |
| 361 | __get_cpu_var(rcu_bh_data).nxtlist) |
| 362 | set_need_resched(); |
| 363 | } |
| 364 | |
| 365 | #ifdef CONFIG_SMP |
| 366 | |
| 367 | /* |
| 368 | * Snapshot the specified CPU's dynticks counter so that we can later |
| 369 | * credit them with an implicit quiescent state. Return 1 if this CPU |
| 370 | * is in dynticks idle mode, which is an extended quiescent state. |
| 371 | */ |
| 372 | static int dyntick_save_progress_counter(struct rcu_data *rdp) |
| 373 | { |
| 374 | int ret; |
| 375 | int snap; |
| 376 | int snap_nmi; |
| 377 | |
| 378 | snap = rdp->dynticks->dynticks; |
| 379 | snap_nmi = rdp->dynticks->dynticks_nmi; |
| 380 | smp_mb(); /* Order sampling of snap with end of grace period. */ |
| 381 | rdp->dynticks_snap = snap; |
| 382 | rdp->dynticks_nmi_snap = snap_nmi; |
| 383 | ret = ((snap & 0x1) == 0) && ((snap_nmi & 0x1) == 0); |
| 384 | if (ret) |
| 385 | rdp->dynticks_fqs++; |
| 386 | return ret; |
| 387 | } |
| 388 | |
| 389 | /* |
| 390 | * Return true if the specified CPU has passed through a quiescent |
| 391 | * state by virtue of being in or having passed through an dynticks |
| 392 | * idle state since the last call to dyntick_save_progress_counter() |
| 393 | * for this same CPU. |
| 394 | */ |
| 395 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) |
| 396 | { |
| 397 | long curr; |
| 398 | long curr_nmi; |
| 399 | long snap; |
| 400 | long snap_nmi; |
| 401 | |
| 402 | curr = rdp->dynticks->dynticks; |
| 403 | snap = rdp->dynticks_snap; |
| 404 | curr_nmi = rdp->dynticks->dynticks_nmi; |
| 405 | snap_nmi = rdp->dynticks_nmi_snap; |
| 406 | smp_mb(); /* force ordering with cpu entering/leaving dynticks. */ |
| 407 | |
| 408 | /* |
| 409 | * If the CPU passed through or entered a dynticks idle phase with |
| 410 | * no active irq/NMI handlers, then we can safely pretend that the CPU |
| 411 | * already acknowledged the request to pass through a quiescent |
| 412 | * state. Either way, that CPU cannot possibly be in an RCU |
| 413 | * read-side critical section that started before the beginning |
| 414 | * of the current RCU grace period. |
| 415 | */ |
| 416 | if ((curr != snap || (curr & 0x1) == 0) && |
| 417 | (curr_nmi != snap_nmi || (curr_nmi & 0x1) == 0)) { |
| 418 | rdp->dynticks_fqs++; |
| 419 | return 1; |
| 420 | } |
| 421 | |
| 422 | /* Go check for the CPU being offline. */ |
| 423 | return rcu_implicit_offline_qs(rdp); |
| 424 | } |
| 425 | |
| 426 | #endif /* #ifdef CONFIG_SMP */ |
| 427 | |
| 428 | #else /* #ifdef CONFIG_NO_HZ */ |
| 429 | |
| 430 | #ifdef CONFIG_SMP |
| 431 | |
| 432 | static int dyntick_save_progress_counter(struct rcu_data *rdp) |
| 433 | { |
| 434 | return 0; |
| 435 | } |
| 436 | |
| 437 | static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) |
| 438 | { |
| 439 | return rcu_implicit_offline_qs(rdp); |
| 440 | } |
| 441 | |
| 442 | #endif /* #ifdef CONFIG_SMP */ |
| 443 | |
| 444 | #endif /* #else #ifdef CONFIG_NO_HZ */ |
| 445 | |
| 446 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
| 447 | |
| 448 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
| 449 | { |
| 450 | rsp->gp_start = jiffies; |
| 451 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK; |
| 452 | } |
| 453 | |
| 454 | static void print_other_cpu_stall(struct rcu_state *rsp) |
| 455 | { |
| 456 | int cpu; |
| 457 | long delta; |
| 458 | unsigned long flags; |
| 459 | struct rcu_node *rnp = rcu_get_root(rsp); |
| 460 | |
| 461 | /* Only let one CPU complain about others per time interval. */ |
| 462 | |
| 463 | raw_spin_lock_irqsave(&rnp->lock, flags); |
| 464 | delta = jiffies - rsp->jiffies_stall; |
| 465 | if (delta < RCU_STALL_RAT_DELAY || !rcu_gp_in_progress(rsp)) { |
| 466 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 467 | return; |
| 468 | } |
| 469 | rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK; |
| 470 | |
| 471 | /* |
| 472 | * Now rat on any tasks that got kicked up to the root rcu_node |
| 473 | * due to CPU offlining. |
| 474 | */ |
| 475 | rcu_print_task_stall(rnp); |
| 476 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 477 | |
| 478 | /* OK, time to rat on our buddy... */ |
| 479 | |
| 480 | printk(KERN_ERR "INFO: RCU detected CPU stalls:"); |
| 481 | rcu_for_each_leaf_node(rsp, rnp) { |
| 482 | raw_spin_lock_irqsave(&rnp->lock, flags); |
| 483 | rcu_print_task_stall(rnp); |
| 484 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 485 | if (rnp->qsmask == 0) |
| 486 | continue; |
| 487 | for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++) |
| 488 | if (rnp->qsmask & (1UL << cpu)) |
| 489 | printk(" %d", rnp->grplo + cpu); |
| 490 | } |
| 491 | printk(" (detected by %d, t=%ld jiffies)\n", |
| 492 | smp_processor_id(), (long)(jiffies - rsp->gp_start)); |
| 493 | trigger_all_cpu_backtrace(); |
| 494 | |
| 495 | /* If so configured, complain about tasks blocking the grace period. */ |
| 496 | |
| 497 | rcu_print_detail_task_stall(rsp); |
| 498 | |
| 499 | force_quiescent_state(rsp, 0); /* Kick them all. */ |
| 500 | } |
| 501 | |
| 502 | static void print_cpu_stall(struct rcu_state *rsp) |
| 503 | { |
| 504 | unsigned long flags; |
| 505 | struct rcu_node *rnp = rcu_get_root(rsp); |
| 506 | |
| 507 | printk(KERN_ERR "INFO: RCU detected CPU %d stall (t=%lu jiffies)\n", |
| 508 | smp_processor_id(), jiffies - rsp->gp_start); |
| 509 | trigger_all_cpu_backtrace(); |
| 510 | |
| 511 | raw_spin_lock_irqsave(&rnp->lock, flags); |
| 512 | if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall)) |
| 513 | rsp->jiffies_stall = |
| 514 | jiffies + RCU_SECONDS_TILL_STALL_RECHECK; |
| 515 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 516 | |
| 517 | set_need_resched(); /* kick ourselves to get things going. */ |
| 518 | } |
| 519 | |
| 520 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) |
| 521 | { |
| 522 | long delta; |
| 523 | struct rcu_node *rnp; |
| 524 | |
| 525 | delta = jiffies - rsp->jiffies_stall; |
| 526 | rnp = rdp->mynode; |
| 527 | if ((rnp->qsmask & rdp->grpmask) && delta >= 0) { |
| 528 | |
| 529 | /* We haven't checked in, so go dump stack. */ |
| 530 | print_cpu_stall(rsp); |
| 531 | |
| 532 | } else if (rcu_gp_in_progress(rsp) && delta >= RCU_STALL_RAT_DELAY) { |
| 533 | |
| 534 | /* They had two time units to dump stack, so complain. */ |
| 535 | print_other_cpu_stall(rsp); |
| 536 | } |
| 537 | } |
| 538 | |
| 539 | #else /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
| 540 | |
| 541 | static void record_gp_stall_check_time(struct rcu_state *rsp) |
| 542 | { |
| 543 | } |
| 544 | |
| 545 | static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp) |
| 546 | { |
| 547 | } |
| 548 | |
| 549 | #endif /* #else #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
| 550 | |
| 551 | /* |
| 552 | * Update CPU-local rcu_data state to record the newly noticed grace period. |
| 553 | * This is used both when we started the grace period and when we notice |
| 554 | * that someone else started the grace period. The caller must hold the |
| 555 | * ->lock of the leaf rcu_node structure corresponding to the current CPU, |
| 556 | * and must have irqs disabled. |
| 557 | */ |
| 558 | static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
| 559 | { |
| 560 | if (rdp->gpnum != rnp->gpnum) { |
| 561 | rdp->qs_pending = 1; |
| 562 | rdp->passed_quiesc = 0; |
| 563 | rdp->gpnum = rnp->gpnum; |
| 564 | } |
| 565 | } |
| 566 | |
| 567 | static void note_new_gpnum(struct rcu_state *rsp, struct rcu_data *rdp) |
| 568 | { |
| 569 | unsigned long flags; |
| 570 | struct rcu_node *rnp; |
| 571 | |
| 572 | local_irq_save(flags); |
| 573 | rnp = rdp->mynode; |
| 574 | if (rdp->gpnum == ACCESS_ONCE(rnp->gpnum) || /* outside lock. */ |
| 575 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
| 576 | local_irq_restore(flags); |
| 577 | return; |
| 578 | } |
| 579 | __note_new_gpnum(rsp, rnp, rdp); |
| 580 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 581 | } |
| 582 | |
| 583 | /* |
| 584 | * Did someone else start a new RCU grace period start since we last |
| 585 | * checked? Update local state appropriately if so. Must be called |
| 586 | * on the CPU corresponding to rdp. |
| 587 | */ |
| 588 | static int |
| 589 | check_for_new_grace_period(struct rcu_state *rsp, struct rcu_data *rdp) |
| 590 | { |
| 591 | unsigned long flags; |
| 592 | int ret = 0; |
| 593 | |
| 594 | local_irq_save(flags); |
| 595 | if (rdp->gpnum != rsp->gpnum) { |
| 596 | note_new_gpnum(rsp, rdp); |
| 597 | ret = 1; |
| 598 | } |
| 599 | local_irq_restore(flags); |
| 600 | return ret; |
| 601 | } |
| 602 | |
| 603 | /* |
| 604 | * Advance this CPU's callbacks, but only if the current grace period |
| 605 | * has ended. This may be called only from the CPU to whom the rdp |
| 606 | * belongs. In addition, the corresponding leaf rcu_node structure's |
| 607 | * ->lock must be held by the caller, with irqs disabled. |
| 608 | */ |
| 609 | static void |
| 610 | __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
| 611 | { |
| 612 | /* Did another grace period end? */ |
| 613 | if (rdp->completed != rnp->completed) { |
| 614 | |
| 615 | /* Advance callbacks. No harm if list empty. */ |
| 616 | rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL]; |
| 617 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL]; |
| 618 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| 619 | |
| 620 | /* Remember that we saw this grace-period completion. */ |
| 621 | rdp->completed = rnp->completed; |
| 622 | } |
| 623 | } |
| 624 | |
| 625 | /* |
| 626 | * Advance this CPU's callbacks, but only if the current grace period |
| 627 | * has ended. This may be called only from the CPU to whom the rdp |
| 628 | * belongs. |
| 629 | */ |
| 630 | static void |
| 631 | rcu_process_gp_end(struct rcu_state *rsp, struct rcu_data *rdp) |
| 632 | { |
| 633 | unsigned long flags; |
| 634 | struct rcu_node *rnp; |
| 635 | |
| 636 | local_irq_save(flags); |
| 637 | rnp = rdp->mynode; |
| 638 | if (rdp->completed == ACCESS_ONCE(rnp->completed) || /* outside lock. */ |
| 639 | !raw_spin_trylock(&rnp->lock)) { /* irqs already off, so later. */ |
| 640 | local_irq_restore(flags); |
| 641 | return; |
| 642 | } |
| 643 | __rcu_process_gp_end(rsp, rnp, rdp); |
| 644 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 645 | } |
| 646 | |
| 647 | /* |
| 648 | * Do per-CPU grace-period initialization for running CPU. The caller |
| 649 | * must hold the lock of the leaf rcu_node structure corresponding to |
| 650 | * this CPU. |
| 651 | */ |
| 652 | static void |
| 653 | rcu_start_gp_per_cpu(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) |
| 654 | { |
| 655 | /* Prior grace period ended, so advance callbacks for current CPU. */ |
| 656 | __rcu_process_gp_end(rsp, rnp, rdp); |
| 657 | |
| 658 | /* |
| 659 | * Because this CPU just now started the new grace period, we know |
| 660 | * that all of its callbacks will be covered by this upcoming grace |
| 661 | * period, even the ones that were registered arbitrarily recently. |
| 662 | * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL. |
| 663 | * |
| 664 | * Other CPUs cannot be sure exactly when the grace period started. |
| 665 | * Therefore, their recently registered callbacks must pass through |
| 666 | * an additional RCU_NEXT_READY stage, so that they will be handled |
| 667 | * by the next RCU grace period. |
| 668 | */ |
| 669 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| 670 | rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| 671 | |
| 672 | /* Set state so that this CPU will detect the next quiescent state. */ |
| 673 | __note_new_gpnum(rsp, rnp, rdp); |
| 674 | } |
| 675 | |
| 676 | /* |
| 677 | * Start a new RCU grace period if warranted, re-initializing the hierarchy |
| 678 | * in preparation for detecting the next grace period. The caller must hold |
| 679 | * the root node's ->lock, which is released before return. Hard irqs must |
| 680 | * be disabled. |
| 681 | */ |
| 682 | static void |
| 683 | rcu_start_gp(struct rcu_state *rsp, unsigned long flags) |
| 684 | __releases(rcu_get_root(rsp)->lock) |
| 685 | { |
| 686 | struct rcu_data *rdp = rsp->rda[smp_processor_id()]; |
| 687 | struct rcu_node *rnp = rcu_get_root(rsp); |
| 688 | |
| 689 | if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) { |
| 690 | if (cpu_needs_another_gp(rsp, rdp)) |
| 691 | rsp->fqs_need_gp = 1; |
| 692 | if (rnp->completed == rsp->completed) { |
| 693 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 694 | return; |
| 695 | } |
| 696 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| 697 | |
| 698 | /* |
| 699 | * Propagate new ->completed value to rcu_node structures |
| 700 | * so that other CPUs don't have to wait until the start |
| 701 | * of the next grace period to process their callbacks. |
| 702 | */ |
| 703 | rcu_for_each_node_breadth_first(rsp, rnp) { |
| 704 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
| 705 | rnp->completed = rsp->completed; |
| 706 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| 707 | } |
| 708 | local_irq_restore(flags); |
| 709 | return; |
| 710 | } |
| 711 | |
| 712 | /* Advance to a new grace period and initialize state. */ |
| 713 | rsp->gpnum++; |
| 714 | WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT); |
| 715 | rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */ |
| 716 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
| 717 | record_gp_stall_check_time(rsp); |
| 718 | |
| 719 | /* Special-case the common single-level case. */ |
| 720 | if (NUM_RCU_NODES == 1) { |
| 721 | rcu_preempt_check_blocked_tasks(rnp); |
| 722 | rnp->qsmask = rnp->qsmaskinit; |
| 723 | rnp->gpnum = rsp->gpnum; |
| 724 | rnp->completed = rsp->completed; |
| 725 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */ |
| 726 | rcu_start_gp_per_cpu(rsp, rnp, rdp); |
| 727 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 728 | return; |
| 729 | } |
| 730 | |
| 731 | raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */ |
| 732 | |
| 733 | |
| 734 | /* Exclude any concurrent CPU-hotplug operations. */ |
| 735 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
| 736 | |
| 737 | /* |
| 738 | * Set the quiescent-state-needed bits in all the rcu_node |
| 739 | * structures for all currently online CPUs in breadth-first |
| 740 | * order, starting from the root rcu_node structure. This |
| 741 | * operation relies on the layout of the hierarchy within the |
| 742 | * rsp->node[] array. Note that other CPUs will access only |
| 743 | * the leaves of the hierarchy, which still indicate that no |
| 744 | * grace period is in progress, at least until the corresponding |
| 745 | * leaf node has been initialized. In addition, we have excluded |
| 746 | * CPU-hotplug operations. |
| 747 | * |
| 748 | * Note that the grace period cannot complete until we finish |
| 749 | * the initialization process, as there will be at least one |
| 750 | * qsmask bit set in the root node until that time, namely the |
| 751 | * one corresponding to this CPU, due to the fact that we have |
| 752 | * irqs disabled. |
| 753 | */ |
| 754 | rcu_for_each_node_breadth_first(rsp, rnp) { |
| 755 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
| 756 | rcu_preempt_check_blocked_tasks(rnp); |
| 757 | rnp->qsmask = rnp->qsmaskinit; |
| 758 | rnp->gpnum = rsp->gpnum; |
| 759 | rnp->completed = rsp->completed; |
| 760 | if (rnp == rdp->mynode) |
| 761 | rcu_start_gp_per_cpu(rsp, rnp, rdp); |
| 762 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| 763 | } |
| 764 | |
| 765 | rnp = rcu_get_root(rsp); |
| 766 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
| 767 | rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */ |
| 768 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| 769 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
| 770 | } |
| 771 | |
| 772 | /* |
| 773 | * Report a full set of quiescent states to the specified rcu_state |
| 774 | * data structure. This involves cleaning up after the prior grace |
| 775 | * period and letting rcu_start_gp() start up the next grace period |
| 776 | * if one is needed. Note that the caller must hold rnp->lock, as |
| 777 | * required by rcu_start_gp(), which will release it. |
| 778 | */ |
| 779 | static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) |
| 780 | __releases(rcu_get_root(rsp)->lock) |
| 781 | { |
| 782 | WARN_ON_ONCE(!rcu_gp_in_progress(rsp)); |
| 783 | rsp->completed = rsp->gpnum; |
| 784 | rsp->signaled = RCU_GP_IDLE; |
| 785 | rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */ |
| 786 | } |
| 787 | |
| 788 | /* |
| 789 | * Similar to rcu_report_qs_rdp(), for which it is a helper function. |
| 790 | * Allows quiescent states for a group of CPUs to be reported at one go |
| 791 | * to the specified rcu_node structure, though all the CPUs in the group |
| 792 | * must be represented by the same rcu_node structure (which need not be |
| 793 | * a leaf rcu_node structure, though it often will be). That structure's |
| 794 | * lock must be held upon entry, and it is released before return. |
| 795 | */ |
| 796 | static void |
| 797 | rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, |
| 798 | struct rcu_node *rnp, unsigned long flags) |
| 799 | __releases(rnp->lock) |
| 800 | { |
| 801 | struct rcu_node *rnp_c; |
| 802 | |
| 803 | /* Walk up the rcu_node hierarchy. */ |
| 804 | for (;;) { |
| 805 | if (!(rnp->qsmask & mask)) { |
| 806 | |
| 807 | /* Our bit has already been cleared, so done. */ |
| 808 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 809 | return; |
| 810 | } |
| 811 | rnp->qsmask &= ~mask; |
| 812 | if (rnp->qsmask != 0 || rcu_preempted_readers(rnp)) { |
| 813 | |
| 814 | /* Other bits still set at this level, so done. */ |
| 815 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 816 | return; |
| 817 | } |
| 818 | mask = rnp->grpmask; |
| 819 | if (rnp->parent == NULL) { |
| 820 | |
| 821 | /* No more levels. Exit loop holding root lock. */ |
| 822 | |
| 823 | break; |
| 824 | } |
| 825 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 826 | rnp_c = rnp; |
| 827 | rnp = rnp->parent; |
| 828 | raw_spin_lock_irqsave(&rnp->lock, flags); |
| 829 | WARN_ON_ONCE(rnp_c->qsmask); |
| 830 | } |
| 831 | |
| 832 | /* |
| 833 | * Get here if we are the last CPU to pass through a quiescent |
| 834 | * state for this grace period. Invoke rcu_report_qs_rsp() |
| 835 | * to clean up and start the next grace period if one is needed. |
| 836 | */ |
| 837 | rcu_report_qs_rsp(rsp, flags); /* releases rnp->lock. */ |
| 838 | } |
| 839 | |
| 840 | /* |
| 841 | * Record a quiescent state for the specified CPU to that CPU's rcu_data |
| 842 | * structure. This must be either called from the specified CPU, or |
| 843 | * called when the specified CPU is known to be offline (and when it is |
| 844 | * also known that no other CPU is concurrently trying to help the offline |
| 845 | * CPU). The lastcomp argument is used to make sure we are still in the |
| 846 | * grace period of interest. We don't want to end the current grace period |
| 847 | * based on quiescent states detected in an earlier grace period! |
| 848 | */ |
| 849 | static void |
| 850 | rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastcomp) |
| 851 | { |
| 852 | unsigned long flags; |
| 853 | unsigned long mask; |
| 854 | struct rcu_node *rnp; |
| 855 | |
| 856 | rnp = rdp->mynode; |
| 857 | raw_spin_lock_irqsave(&rnp->lock, flags); |
| 858 | if (lastcomp != rnp->completed) { |
| 859 | |
| 860 | /* |
| 861 | * Someone beat us to it for this grace period, so leave. |
| 862 | * The race with GP start is resolved by the fact that we |
| 863 | * hold the leaf rcu_node lock, so that the per-CPU bits |
| 864 | * cannot yet be initialized -- so we would simply find our |
| 865 | * CPU's bit already cleared in rcu_report_qs_rnp() if this |
| 866 | * race occurred. |
| 867 | */ |
| 868 | rdp->passed_quiesc = 0; /* try again later! */ |
| 869 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 870 | return; |
| 871 | } |
| 872 | mask = rdp->grpmask; |
| 873 | if ((rnp->qsmask & mask) == 0) { |
| 874 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 875 | } else { |
| 876 | rdp->qs_pending = 0; |
| 877 | |
| 878 | /* |
| 879 | * This GP can't end until cpu checks in, so all of our |
| 880 | * callbacks can be processed during the next GP. |
| 881 | */ |
| 882 | rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL]; |
| 883 | |
| 884 | rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */ |
| 885 | } |
| 886 | } |
| 887 | |
| 888 | /* |
| 889 | * Check to see if there is a new grace period of which this CPU |
| 890 | * is not yet aware, and if so, set up local rcu_data state for it. |
| 891 | * Otherwise, see if this CPU has just passed through its first |
| 892 | * quiescent state for this grace period, and record that fact if so. |
| 893 | */ |
| 894 | static void |
| 895 | rcu_check_quiescent_state(struct rcu_state *rsp, struct rcu_data *rdp) |
| 896 | { |
| 897 | /* If there is now a new grace period, record and return. */ |
| 898 | if (check_for_new_grace_period(rsp, rdp)) |
| 899 | return; |
| 900 | |
| 901 | /* |
| 902 | * Does this CPU still need to do its part for current grace period? |
| 903 | * If no, return and let the other CPUs do their part as well. |
| 904 | */ |
| 905 | if (!rdp->qs_pending) |
| 906 | return; |
| 907 | |
| 908 | /* |
| 909 | * Was there a quiescent state since the beginning of the grace |
| 910 | * period? If no, then exit and wait for the next call. |
| 911 | */ |
| 912 | if (!rdp->passed_quiesc) |
| 913 | return; |
| 914 | |
| 915 | /* |
| 916 | * Tell RCU we are done (but rcu_report_qs_rdp() will be the |
| 917 | * judge of that). |
| 918 | */ |
| 919 | rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesc_completed); |
| 920 | } |
| 921 | |
| 922 | #ifdef CONFIG_HOTPLUG_CPU |
| 923 | |
| 924 | /* |
| 925 | * Move a dying CPU's RCU callbacks to the ->orphan_cbs_list for the |
| 926 | * specified flavor of RCU. The callbacks will be adopted by the next |
| 927 | * _rcu_barrier() invocation or by the CPU_DEAD notifier, whichever |
| 928 | * comes first. Because this is invoked from the CPU_DYING notifier, |
| 929 | * irqs are already disabled. |
| 930 | */ |
| 931 | static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp) |
| 932 | { |
| 933 | int i; |
| 934 | struct rcu_data *rdp = rsp->rda[smp_processor_id()]; |
| 935 | |
| 936 | if (rdp->nxtlist == NULL) |
| 937 | return; /* irqs disabled, so comparison is stable. */ |
| 938 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
| 939 | *rsp->orphan_cbs_tail = rdp->nxtlist; |
| 940 | rsp->orphan_cbs_tail = rdp->nxttail[RCU_NEXT_TAIL]; |
| 941 | rdp->nxtlist = NULL; |
| 942 | for (i = 0; i < RCU_NEXT_SIZE; i++) |
| 943 | rdp->nxttail[i] = &rdp->nxtlist; |
| 944 | rsp->orphan_qlen += rdp->qlen; |
| 945 | rdp->qlen = 0; |
| 946 | raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ |
| 947 | } |
| 948 | |
| 949 | /* |
| 950 | * Adopt previously orphaned RCU callbacks. |
| 951 | */ |
| 952 | static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) |
| 953 | { |
| 954 | unsigned long flags; |
| 955 | struct rcu_data *rdp; |
| 956 | |
| 957 | raw_spin_lock_irqsave(&rsp->onofflock, flags); |
| 958 | rdp = rsp->rda[smp_processor_id()]; |
| 959 | if (rsp->orphan_cbs_list == NULL) { |
| 960 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
| 961 | return; |
| 962 | } |
| 963 | *rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_cbs_list; |
| 964 | rdp->nxttail[RCU_NEXT_TAIL] = rsp->orphan_cbs_tail; |
| 965 | rdp->qlen += rsp->orphan_qlen; |
| 966 | rsp->orphan_cbs_list = NULL; |
| 967 | rsp->orphan_cbs_tail = &rsp->orphan_cbs_list; |
| 968 | rsp->orphan_qlen = 0; |
| 969 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
| 970 | } |
| 971 | |
| 972 | /* |
| 973 | * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy |
| 974 | * and move all callbacks from the outgoing CPU to the current one. |
| 975 | */ |
| 976 | static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp) |
| 977 | { |
| 978 | unsigned long flags; |
| 979 | unsigned long mask; |
| 980 | int need_report = 0; |
| 981 | struct rcu_data *rdp = rsp->rda[cpu]; |
| 982 | struct rcu_node *rnp; |
| 983 | |
| 984 | /* Exclude any attempts to start a new grace period. */ |
| 985 | raw_spin_lock_irqsave(&rsp->onofflock, flags); |
| 986 | |
| 987 | /* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */ |
| 988 | rnp = rdp->mynode; /* this is the outgoing CPU's rnp. */ |
| 989 | mask = rdp->grpmask; /* rnp->grplo is constant. */ |
| 990 | do { |
| 991 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
| 992 | rnp->qsmaskinit &= ~mask; |
| 993 | if (rnp->qsmaskinit != 0) { |
| 994 | if (rnp != rdp->mynode) |
| 995 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| 996 | break; |
| 997 | } |
| 998 | if (rnp == rdp->mynode) |
| 999 | need_report = rcu_preempt_offline_tasks(rsp, rnp, rdp); |
| 1000 | else |
| 1001 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| 1002 | mask = rnp->grpmask; |
| 1003 | rnp = rnp->parent; |
| 1004 | } while (rnp != NULL); |
| 1005 | |
| 1006 | /* |
| 1007 | * We still hold the leaf rcu_node structure lock here, and |
| 1008 | * irqs are still disabled. The reason for this subterfuge is |
| 1009 | * because invoking rcu_report_unblock_qs_rnp() with ->onofflock |
| 1010 | * held leads to deadlock. |
| 1011 | */ |
| 1012 | raw_spin_unlock(&rsp->onofflock); /* irqs remain disabled. */ |
| 1013 | rnp = rdp->mynode; |
| 1014 | if (need_report & RCU_OFL_TASKS_NORM_GP) |
| 1015 | rcu_report_unblock_qs_rnp(rnp, flags); |
| 1016 | else |
| 1017 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 1018 | if (need_report & RCU_OFL_TASKS_EXP_GP) |
| 1019 | rcu_report_exp_rnp(rsp, rnp); |
| 1020 | |
| 1021 | rcu_adopt_orphan_cbs(rsp); |
| 1022 | } |
| 1023 | |
| 1024 | /* |
| 1025 | * Remove the specified CPU from the RCU hierarchy and move any pending |
| 1026 | * callbacks that it might have to the current CPU. This code assumes |
| 1027 | * that at least one CPU in the system will remain running at all times. |
| 1028 | * Any attempt to offline -all- CPUs is likely to strand RCU callbacks. |
| 1029 | */ |
| 1030 | static void rcu_offline_cpu(int cpu) |
| 1031 | { |
| 1032 | __rcu_offline_cpu(cpu, &rcu_sched_state); |
| 1033 | __rcu_offline_cpu(cpu, &rcu_bh_state); |
| 1034 | rcu_preempt_offline_cpu(cpu); |
| 1035 | } |
| 1036 | |
| 1037 | #else /* #ifdef CONFIG_HOTPLUG_CPU */ |
| 1038 | |
| 1039 | static void rcu_send_cbs_to_orphanage(struct rcu_state *rsp) |
| 1040 | { |
| 1041 | } |
| 1042 | |
| 1043 | static void rcu_adopt_orphan_cbs(struct rcu_state *rsp) |
| 1044 | { |
| 1045 | } |
| 1046 | |
| 1047 | static void rcu_offline_cpu(int cpu) |
| 1048 | { |
| 1049 | } |
| 1050 | |
| 1051 | #endif /* #else #ifdef CONFIG_HOTPLUG_CPU */ |
| 1052 | |
| 1053 | /* |
| 1054 | * Invoke any RCU callbacks that have made it to the end of their grace |
| 1055 | * period. Thottle as specified by rdp->blimit. |
| 1056 | */ |
| 1057 | static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp) |
| 1058 | { |
| 1059 | unsigned long flags; |
| 1060 | struct rcu_head *next, *list, **tail; |
| 1061 | int count; |
| 1062 | |
| 1063 | /* If no callbacks are ready, just return.*/ |
| 1064 | if (!cpu_has_callbacks_ready_to_invoke(rdp)) |
| 1065 | return; |
| 1066 | |
| 1067 | /* |
| 1068 | * Extract the list of ready callbacks, disabling to prevent |
| 1069 | * races with call_rcu() from interrupt handlers. |
| 1070 | */ |
| 1071 | local_irq_save(flags); |
| 1072 | list = rdp->nxtlist; |
| 1073 | rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL]; |
| 1074 | *rdp->nxttail[RCU_DONE_TAIL] = NULL; |
| 1075 | tail = rdp->nxttail[RCU_DONE_TAIL]; |
| 1076 | for (count = RCU_NEXT_SIZE - 1; count >= 0; count--) |
| 1077 | if (rdp->nxttail[count] == rdp->nxttail[RCU_DONE_TAIL]) |
| 1078 | rdp->nxttail[count] = &rdp->nxtlist; |
| 1079 | local_irq_restore(flags); |
| 1080 | |
| 1081 | /* Invoke callbacks. */ |
| 1082 | count = 0; |
| 1083 | while (list) { |
| 1084 | next = list->next; |
| 1085 | prefetch(next); |
| 1086 | list->func(list); |
| 1087 | list = next; |
| 1088 | if (++count >= rdp->blimit) |
| 1089 | break; |
| 1090 | } |
| 1091 | |
| 1092 | local_irq_save(flags); |
| 1093 | |
| 1094 | /* Update count, and requeue any remaining callbacks. */ |
| 1095 | rdp->qlen -= count; |
| 1096 | if (list != NULL) { |
| 1097 | *tail = rdp->nxtlist; |
| 1098 | rdp->nxtlist = list; |
| 1099 | for (count = 0; count < RCU_NEXT_SIZE; count++) |
| 1100 | if (&rdp->nxtlist == rdp->nxttail[count]) |
| 1101 | rdp->nxttail[count] = tail; |
| 1102 | else |
| 1103 | break; |
| 1104 | } |
| 1105 | |
| 1106 | /* Reinstate batch limit if we have worked down the excess. */ |
| 1107 | if (rdp->blimit == LONG_MAX && rdp->qlen <= qlowmark) |
| 1108 | rdp->blimit = blimit; |
| 1109 | |
| 1110 | /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ |
| 1111 | if (rdp->qlen == 0 && rdp->qlen_last_fqs_check != 0) { |
| 1112 | rdp->qlen_last_fqs_check = 0; |
| 1113 | rdp->n_force_qs_snap = rsp->n_force_qs; |
| 1114 | } else if (rdp->qlen < rdp->qlen_last_fqs_check - qhimark) |
| 1115 | rdp->qlen_last_fqs_check = rdp->qlen; |
| 1116 | |
| 1117 | local_irq_restore(flags); |
| 1118 | |
| 1119 | /* Re-raise the RCU softirq if there are callbacks remaining. */ |
| 1120 | if (cpu_has_callbacks_ready_to_invoke(rdp)) |
| 1121 | raise_softirq(RCU_SOFTIRQ); |
| 1122 | } |
| 1123 | |
| 1124 | /* |
| 1125 | * Check to see if this CPU is in a non-context-switch quiescent state |
| 1126 | * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). |
| 1127 | * Also schedule the RCU softirq handler. |
| 1128 | * |
| 1129 | * This function must be called with hardirqs disabled. It is normally |
| 1130 | * invoked from the scheduling-clock interrupt. If rcu_pending returns |
| 1131 | * false, there is no point in invoking rcu_check_callbacks(). |
| 1132 | */ |
| 1133 | void rcu_check_callbacks(int cpu, int user) |
| 1134 | { |
| 1135 | if (!rcu_pending(cpu)) |
| 1136 | return; /* if nothing for RCU to do. */ |
| 1137 | if (user || |
| 1138 | (idle_cpu(cpu) && rcu_scheduler_active && |
| 1139 | !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) { |
| 1140 | |
| 1141 | /* |
| 1142 | * Get here if this CPU took its interrupt from user |
| 1143 | * mode or from the idle loop, and if this is not a |
| 1144 | * nested interrupt. In this case, the CPU is in |
| 1145 | * a quiescent state, so note it. |
| 1146 | * |
| 1147 | * No memory barrier is required here because both |
| 1148 | * rcu_sched_qs() and rcu_bh_qs() reference only CPU-local |
| 1149 | * variables that other CPUs neither access nor modify, |
| 1150 | * at least not while the corresponding CPU is online. |
| 1151 | */ |
| 1152 | |
| 1153 | rcu_sched_qs(cpu); |
| 1154 | rcu_bh_qs(cpu); |
| 1155 | |
| 1156 | } else if (!in_softirq()) { |
| 1157 | |
| 1158 | /* |
| 1159 | * Get here if this CPU did not take its interrupt from |
| 1160 | * softirq, in other words, if it is not interrupting |
| 1161 | * a rcu_bh read-side critical section. This is an _bh |
| 1162 | * critical section, so note it. |
| 1163 | */ |
| 1164 | |
| 1165 | rcu_bh_qs(cpu); |
| 1166 | } |
| 1167 | rcu_preempt_check_callbacks(cpu); |
| 1168 | raise_softirq(RCU_SOFTIRQ); |
| 1169 | } |
| 1170 | |
| 1171 | #ifdef CONFIG_SMP |
| 1172 | |
| 1173 | /* |
| 1174 | * Scan the leaf rcu_node structures, processing dyntick state for any that |
| 1175 | * have not yet encountered a quiescent state, using the function specified. |
| 1176 | * The caller must have suppressed start of new grace periods. |
| 1177 | */ |
| 1178 | static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *)) |
| 1179 | { |
| 1180 | unsigned long bit; |
| 1181 | int cpu; |
| 1182 | unsigned long flags; |
| 1183 | unsigned long mask; |
| 1184 | struct rcu_node *rnp; |
| 1185 | |
| 1186 | rcu_for_each_leaf_node(rsp, rnp) { |
| 1187 | mask = 0; |
| 1188 | raw_spin_lock_irqsave(&rnp->lock, flags); |
| 1189 | if (!rcu_gp_in_progress(rsp)) { |
| 1190 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 1191 | return; |
| 1192 | } |
| 1193 | if (rnp->qsmask == 0) { |
| 1194 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 1195 | continue; |
| 1196 | } |
| 1197 | cpu = rnp->grplo; |
| 1198 | bit = 1; |
| 1199 | for (; cpu <= rnp->grphi; cpu++, bit <<= 1) { |
| 1200 | if ((rnp->qsmask & bit) != 0 && f(rsp->rda[cpu])) |
| 1201 | mask |= bit; |
| 1202 | } |
| 1203 | if (mask != 0) { |
| 1204 | |
| 1205 | /* rcu_report_qs_rnp() releases rnp->lock. */ |
| 1206 | rcu_report_qs_rnp(mask, rsp, rnp, flags); |
| 1207 | continue; |
| 1208 | } |
| 1209 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 1210 | } |
| 1211 | } |
| 1212 | |
| 1213 | /* |
| 1214 | * Force quiescent states on reluctant CPUs, and also detect which |
| 1215 | * CPUs are in dyntick-idle mode. |
| 1216 | */ |
| 1217 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) |
| 1218 | { |
| 1219 | unsigned long flags; |
| 1220 | struct rcu_node *rnp = rcu_get_root(rsp); |
| 1221 | |
| 1222 | if (!rcu_gp_in_progress(rsp)) |
| 1223 | return; /* No grace period in progress, nothing to force. */ |
| 1224 | if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) { |
| 1225 | rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */ |
| 1226 | return; /* Someone else is already on the job. */ |
| 1227 | } |
| 1228 | if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies)) |
| 1229 | goto unlock_fqs_ret; /* no emergency and done recently. */ |
| 1230 | rsp->n_force_qs++; |
| 1231 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
| 1232 | rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS; |
| 1233 | if(!rcu_gp_in_progress(rsp)) { |
| 1234 | rsp->n_force_qs_ngp++; |
| 1235 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
| 1236 | goto unlock_fqs_ret; /* no GP in progress, time updated. */ |
| 1237 | } |
| 1238 | rsp->fqs_active = 1; |
| 1239 | switch (rsp->signaled) { |
| 1240 | case RCU_GP_IDLE: |
| 1241 | case RCU_GP_INIT: |
| 1242 | |
| 1243 | break; /* grace period idle or initializing, ignore. */ |
| 1244 | |
| 1245 | case RCU_SAVE_DYNTICK: |
| 1246 | if (RCU_SIGNAL_INIT != RCU_SAVE_DYNTICK) |
| 1247 | break; /* So gcc recognizes the dead code. */ |
| 1248 | |
| 1249 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
| 1250 | |
| 1251 | /* Record dyntick-idle state. */ |
| 1252 | force_qs_rnp(rsp, dyntick_save_progress_counter); |
| 1253 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
| 1254 | if (rcu_gp_in_progress(rsp)) |
| 1255 | rsp->signaled = RCU_FORCE_QS; |
| 1256 | break; |
| 1257 | |
| 1258 | case RCU_FORCE_QS: |
| 1259 | |
| 1260 | /* Check dyntick-idle state, send IPI to laggarts. */ |
| 1261 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
| 1262 | force_qs_rnp(rsp, rcu_implicit_dynticks_qs); |
| 1263 | |
| 1264 | /* Leave state in case more forcing is required. */ |
| 1265 | |
| 1266 | raw_spin_lock(&rnp->lock); /* irqs already disabled */ |
| 1267 | break; |
| 1268 | } |
| 1269 | rsp->fqs_active = 0; |
| 1270 | if (rsp->fqs_need_gp) { |
| 1271 | raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */ |
| 1272 | rsp->fqs_need_gp = 0; |
| 1273 | rcu_start_gp(rsp, flags); /* releases rnp->lock */ |
| 1274 | return; |
| 1275 | } |
| 1276 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ |
| 1277 | unlock_fqs_ret: |
| 1278 | raw_spin_unlock_irqrestore(&rsp->fqslock, flags); |
| 1279 | } |
| 1280 | |
| 1281 | #else /* #ifdef CONFIG_SMP */ |
| 1282 | |
| 1283 | static void force_quiescent_state(struct rcu_state *rsp, int relaxed) |
| 1284 | { |
| 1285 | set_need_resched(); |
| 1286 | } |
| 1287 | |
| 1288 | #endif /* #else #ifdef CONFIG_SMP */ |
| 1289 | |
| 1290 | /* |
| 1291 | * This does the RCU processing work from softirq context for the |
| 1292 | * specified rcu_state and rcu_data structures. This may be called |
| 1293 | * only from the CPU to whom the rdp belongs. |
| 1294 | */ |
| 1295 | static void |
| 1296 | __rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp) |
| 1297 | { |
| 1298 | unsigned long flags; |
| 1299 | |
| 1300 | WARN_ON_ONCE(rdp->beenonline == 0); |
| 1301 | |
| 1302 | /* |
| 1303 | * If an RCU GP has gone long enough, go check for dyntick |
| 1304 | * idle CPUs and, if needed, send resched IPIs. |
| 1305 | */ |
| 1306 | if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) |
| 1307 | force_quiescent_state(rsp, 1); |
| 1308 | |
| 1309 | /* |
| 1310 | * Advance callbacks in response to end of earlier grace |
| 1311 | * period that some other CPU ended. |
| 1312 | */ |
| 1313 | rcu_process_gp_end(rsp, rdp); |
| 1314 | |
| 1315 | /* Update RCU state based on any recent quiescent states. */ |
| 1316 | rcu_check_quiescent_state(rsp, rdp); |
| 1317 | |
| 1318 | /* Does this CPU require a not-yet-started grace period? */ |
| 1319 | if (cpu_needs_another_gp(rsp, rdp)) { |
| 1320 | raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags); |
| 1321 | rcu_start_gp(rsp, flags); /* releases above lock */ |
| 1322 | } |
| 1323 | |
| 1324 | /* If there are callbacks ready, invoke them. */ |
| 1325 | rcu_do_batch(rsp, rdp); |
| 1326 | } |
| 1327 | |
| 1328 | /* |
| 1329 | * Do softirq processing for the current CPU. |
| 1330 | */ |
| 1331 | static void rcu_process_callbacks(struct softirq_action *unused) |
| 1332 | { |
| 1333 | /* |
| 1334 | * Memory references from any prior RCU read-side critical sections |
| 1335 | * executed by the interrupted code must be seen before any RCU |
| 1336 | * grace-period manipulations below. |
| 1337 | */ |
| 1338 | smp_mb(); /* See above block comment. */ |
| 1339 | |
| 1340 | __rcu_process_callbacks(&rcu_sched_state, |
| 1341 | &__get_cpu_var(rcu_sched_data)); |
| 1342 | __rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data)); |
| 1343 | rcu_preempt_process_callbacks(); |
| 1344 | |
| 1345 | /* |
| 1346 | * Memory references from any later RCU read-side critical sections |
| 1347 | * executed by the interrupted code must be seen after any RCU |
| 1348 | * grace-period manipulations above. |
| 1349 | */ |
| 1350 | smp_mb(); /* See above block comment. */ |
| 1351 | |
| 1352 | /* If we are last CPU on way to dyntick-idle mode, accelerate it. */ |
| 1353 | rcu_needs_cpu_flush(); |
| 1354 | } |
| 1355 | |
| 1356 | static void |
| 1357 | __call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu), |
| 1358 | struct rcu_state *rsp) |
| 1359 | { |
| 1360 | unsigned long flags; |
| 1361 | struct rcu_data *rdp; |
| 1362 | |
| 1363 | head->func = func; |
| 1364 | head->next = NULL; |
| 1365 | |
| 1366 | smp_mb(); /* Ensure RCU update seen before callback registry. */ |
| 1367 | |
| 1368 | /* |
| 1369 | * Opportunistically note grace-period endings and beginnings. |
| 1370 | * Note that we might see a beginning right after we see an |
| 1371 | * end, but never vice versa, since this CPU has to pass through |
| 1372 | * a quiescent state betweentimes. |
| 1373 | */ |
| 1374 | local_irq_save(flags); |
| 1375 | rdp = rsp->rda[smp_processor_id()]; |
| 1376 | rcu_process_gp_end(rsp, rdp); |
| 1377 | check_for_new_grace_period(rsp, rdp); |
| 1378 | |
| 1379 | /* Add the callback to our list. */ |
| 1380 | *rdp->nxttail[RCU_NEXT_TAIL] = head; |
| 1381 | rdp->nxttail[RCU_NEXT_TAIL] = &head->next; |
| 1382 | |
| 1383 | /* Start a new grace period if one not already started. */ |
| 1384 | if (!rcu_gp_in_progress(rsp)) { |
| 1385 | unsigned long nestflag; |
| 1386 | struct rcu_node *rnp_root = rcu_get_root(rsp); |
| 1387 | |
| 1388 | raw_spin_lock_irqsave(&rnp_root->lock, nestflag); |
| 1389 | rcu_start_gp(rsp, nestflag); /* releases rnp_root->lock. */ |
| 1390 | } |
| 1391 | |
| 1392 | /* |
| 1393 | * Force the grace period if too many callbacks or too long waiting. |
| 1394 | * Enforce hysteresis, and don't invoke force_quiescent_state() |
| 1395 | * if some other CPU has recently done so. Also, don't bother |
| 1396 | * invoking force_quiescent_state() if the newly enqueued callback |
| 1397 | * is the only one waiting for a grace period to complete. |
| 1398 | */ |
| 1399 | if (unlikely(++rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) { |
| 1400 | rdp->blimit = LONG_MAX; |
| 1401 | if (rsp->n_force_qs == rdp->n_force_qs_snap && |
| 1402 | *rdp->nxttail[RCU_DONE_TAIL] != head) |
| 1403 | force_quiescent_state(rsp, 0); |
| 1404 | rdp->n_force_qs_snap = rsp->n_force_qs; |
| 1405 | rdp->qlen_last_fqs_check = rdp->qlen; |
| 1406 | } else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) |
| 1407 | force_quiescent_state(rsp, 1); |
| 1408 | local_irq_restore(flags); |
| 1409 | } |
| 1410 | |
| 1411 | /* |
| 1412 | * Queue an RCU-sched callback for invocation after a grace period. |
| 1413 | */ |
| 1414 | void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
| 1415 | { |
| 1416 | __call_rcu(head, func, &rcu_sched_state); |
| 1417 | } |
| 1418 | EXPORT_SYMBOL_GPL(call_rcu_sched); |
| 1419 | |
| 1420 | /* |
| 1421 | * Queue an RCU for invocation after a quicker grace period. |
| 1422 | */ |
| 1423 | void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu)) |
| 1424 | { |
| 1425 | __call_rcu(head, func, &rcu_bh_state); |
| 1426 | } |
| 1427 | EXPORT_SYMBOL_GPL(call_rcu_bh); |
| 1428 | |
| 1429 | /** |
| 1430 | * synchronize_sched - wait until an rcu-sched grace period has elapsed. |
| 1431 | * |
| 1432 | * Control will return to the caller some time after a full rcu-sched |
| 1433 | * grace period has elapsed, in other words after all currently executing |
| 1434 | * rcu-sched read-side critical sections have completed. These read-side |
| 1435 | * critical sections are delimited by rcu_read_lock_sched() and |
| 1436 | * rcu_read_unlock_sched(), and may be nested. Note that preempt_disable(), |
| 1437 | * local_irq_disable(), and so on may be used in place of |
| 1438 | * rcu_read_lock_sched(). |
| 1439 | * |
| 1440 | * This means that all preempt_disable code sequences, including NMI and |
| 1441 | * hardware-interrupt handlers, in progress on entry will have completed |
| 1442 | * before this primitive returns. However, this does not guarantee that |
| 1443 | * softirq handlers will have completed, since in some kernels, these |
| 1444 | * handlers can run in process context, and can block. |
| 1445 | * |
| 1446 | * This primitive provides the guarantees made by the (now removed) |
| 1447 | * synchronize_kernel() API. In contrast, synchronize_rcu() only |
| 1448 | * guarantees that rcu_read_lock() sections will have completed. |
| 1449 | * In "classic RCU", these two guarantees happen to be one and |
| 1450 | * the same, but can differ in realtime RCU implementations. |
| 1451 | */ |
| 1452 | void synchronize_sched(void) |
| 1453 | { |
| 1454 | struct rcu_synchronize rcu; |
| 1455 | |
| 1456 | if (rcu_blocking_is_gp()) |
| 1457 | return; |
| 1458 | |
| 1459 | init_completion(&rcu.completion); |
| 1460 | /* Will wake me after RCU finished. */ |
| 1461 | call_rcu_sched(&rcu.head, wakeme_after_rcu); |
| 1462 | /* Wait for it. */ |
| 1463 | wait_for_completion(&rcu.completion); |
| 1464 | } |
| 1465 | EXPORT_SYMBOL_GPL(synchronize_sched); |
| 1466 | |
| 1467 | /** |
| 1468 | * synchronize_rcu_bh - wait until an rcu_bh grace period has elapsed. |
| 1469 | * |
| 1470 | * Control will return to the caller some time after a full rcu_bh grace |
| 1471 | * period has elapsed, in other words after all currently executing rcu_bh |
| 1472 | * read-side critical sections have completed. RCU read-side critical |
| 1473 | * sections are delimited by rcu_read_lock_bh() and rcu_read_unlock_bh(), |
| 1474 | * and may be nested. |
| 1475 | */ |
| 1476 | void synchronize_rcu_bh(void) |
| 1477 | { |
| 1478 | struct rcu_synchronize rcu; |
| 1479 | |
| 1480 | if (rcu_blocking_is_gp()) |
| 1481 | return; |
| 1482 | |
| 1483 | init_completion(&rcu.completion); |
| 1484 | /* Will wake me after RCU finished. */ |
| 1485 | call_rcu_bh(&rcu.head, wakeme_after_rcu); |
| 1486 | /* Wait for it. */ |
| 1487 | wait_for_completion(&rcu.completion); |
| 1488 | } |
| 1489 | EXPORT_SYMBOL_GPL(synchronize_rcu_bh); |
| 1490 | |
| 1491 | /* |
| 1492 | * Check to see if there is any immediate RCU-related work to be done |
| 1493 | * by the current CPU, for the specified type of RCU, returning 1 if so. |
| 1494 | * The checks are in order of increasing expense: checks that can be |
| 1495 | * carried out against CPU-local state are performed first. However, |
| 1496 | * we must check for CPU stalls first, else we might not get a chance. |
| 1497 | */ |
| 1498 | static int __rcu_pending(struct rcu_state *rsp, struct rcu_data *rdp) |
| 1499 | { |
| 1500 | struct rcu_node *rnp = rdp->mynode; |
| 1501 | |
| 1502 | rdp->n_rcu_pending++; |
| 1503 | |
| 1504 | /* Check for CPU stalls, if enabled. */ |
| 1505 | check_cpu_stall(rsp, rdp); |
| 1506 | |
| 1507 | /* Is the RCU core waiting for a quiescent state from this CPU? */ |
| 1508 | if (rdp->qs_pending) { |
| 1509 | |
| 1510 | /* |
| 1511 | * If force_quiescent_state() coming soon and this CPU |
| 1512 | * needs a quiescent state, and this is either RCU-sched |
| 1513 | * or RCU-bh, force a local reschedule. |
| 1514 | */ |
| 1515 | if (!rdp->preemptable && |
| 1516 | ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1, |
| 1517 | jiffies)) |
| 1518 | set_need_resched(); |
| 1519 | rdp->n_rp_qs_pending++; |
| 1520 | return 1; |
| 1521 | } |
| 1522 | |
| 1523 | /* Does this CPU have callbacks ready to invoke? */ |
| 1524 | if (cpu_has_callbacks_ready_to_invoke(rdp)) { |
| 1525 | rdp->n_rp_cb_ready++; |
| 1526 | return 1; |
| 1527 | } |
| 1528 | |
| 1529 | /* Has RCU gone idle with this CPU needing another grace period? */ |
| 1530 | if (cpu_needs_another_gp(rsp, rdp)) { |
| 1531 | rdp->n_rp_cpu_needs_gp++; |
| 1532 | return 1; |
| 1533 | } |
| 1534 | |
| 1535 | /* Has another RCU grace period completed? */ |
| 1536 | if (ACCESS_ONCE(rnp->completed) != rdp->completed) { /* outside lock */ |
| 1537 | rdp->n_rp_gp_completed++; |
| 1538 | return 1; |
| 1539 | } |
| 1540 | |
| 1541 | /* Has a new RCU grace period started? */ |
| 1542 | if (ACCESS_ONCE(rnp->gpnum) != rdp->gpnum) { /* outside lock */ |
| 1543 | rdp->n_rp_gp_started++; |
| 1544 | return 1; |
| 1545 | } |
| 1546 | |
| 1547 | /* Has an RCU GP gone long enough to send resched IPIs &c? */ |
| 1548 | if (rcu_gp_in_progress(rsp) && |
| 1549 | ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) { |
| 1550 | rdp->n_rp_need_fqs++; |
| 1551 | return 1; |
| 1552 | } |
| 1553 | |
| 1554 | /* nothing to do */ |
| 1555 | rdp->n_rp_need_nothing++; |
| 1556 | return 0; |
| 1557 | } |
| 1558 | |
| 1559 | /* |
| 1560 | * Check to see if there is any immediate RCU-related work to be done |
| 1561 | * by the current CPU, returning 1 if so. This function is part of the |
| 1562 | * RCU implementation; it is -not- an exported member of the RCU API. |
| 1563 | */ |
| 1564 | static int rcu_pending(int cpu) |
| 1565 | { |
| 1566 | return __rcu_pending(&rcu_sched_state, &per_cpu(rcu_sched_data, cpu)) || |
| 1567 | __rcu_pending(&rcu_bh_state, &per_cpu(rcu_bh_data, cpu)) || |
| 1568 | rcu_preempt_pending(cpu); |
| 1569 | } |
| 1570 | |
| 1571 | /* |
| 1572 | * Check to see if any future RCU-related work will need to be done |
| 1573 | * by the current CPU, even if none need be done immediately, returning |
| 1574 | * 1 if so. |
| 1575 | */ |
| 1576 | static int rcu_needs_cpu_quick_check(int cpu) |
| 1577 | { |
| 1578 | /* RCU callbacks either ready or pending? */ |
| 1579 | return per_cpu(rcu_sched_data, cpu).nxtlist || |
| 1580 | per_cpu(rcu_bh_data, cpu).nxtlist || |
| 1581 | rcu_preempt_needs_cpu(cpu); |
| 1582 | } |
| 1583 | |
| 1584 | static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL}; |
| 1585 | static atomic_t rcu_barrier_cpu_count; |
| 1586 | static DEFINE_MUTEX(rcu_barrier_mutex); |
| 1587 | static struct completion rcu_barrier_completion; |
| 1588 | |
| 1589 | static void rcu_barrier_callback(struct rcu_head *notused) |
| 1590 | { |
| 1591 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) |
| 1592 | complete(&rcu_barrier_completion); |
| 1593 | } |
| 1594 | |
| 1595 | /* |
| 1596 | * Called with preemption disabled, and from cross-cpu IRQ context. |
| 1597 | */ |
| 1598 | static void rcu_barrier_func(void *type) |
| 1599 | { |
| 1600 | int cpu = smp_processor_id(); |
| 1601 | struct rcu_head *head = &per_cpu(rcu_barrier_head, cpu); |
| 1602 | void (*call_rcu_func)(struct rcu_head *head, |
| 1603 | void (*func)(struct rcu_head *head)); |
| 1604 | |
| 1605 | atomic_inc(&rcu_barrier_cpu_count); |
| 1606 | call_rcu_func = type; |
| 1607 | call_rcu_func(head, rcu_barrier_callback); |
| 1608 | } |
| 1609 | |
| 1610 | /* |
| 1611 | * Orchestrate the specified type of RCU barrier, waiting for all |
| 1612 | * RCU callbacks of the specified type to complete. |
| 1613 | */ |
| 1614 | static void _rcu_barrier(struct rcu_state *rsp, |
| 1615 | void (*call_rcu_func)(struct rcu_head *head, |
| 1616 | void (*func)(struct rcu_head *head))) |
| 1617 | { |
| 1618 | BUG_ON(in_interrupt()); |
| 1619 | /* Take mutex to serialize concurrent rcu_barrier() requests. */ |
| 1620 | mutex_lock(&rcu_barrier_mutex); |
| 1621 | init_completion(&rcu_barrier_completion); |
| 1622 | /* |
| 1623 | * Initialize rcu_barrier_cpu_count to 1, then invoke |
| 1624 | * rcu_barrier_func() on each CPU, so that each CPU also has |
| 1625 | * incremented rcu_barrier_cpu_count. Only then is it safe to |
| 1626 | * decrement rcu_barrier_cpu_count -- otherwise the first CPU |
| 1627 | * might complete its grace period before all of the other CPUs |
| 1628 | * did their increment, causing this function to return too |
| 1629 | * early. |
| 1630 | */ |
| 1631 | atomic_set(&rcu_barrier_cpu_count, 1); |
| 1632 | preempt_disable(); /* stop CPU_DYING from filling orphan_cbs_list */ |
| 1633 | rcu_adopt_orphan_cbs(rsp); |
| 1634 | on_each_cpu(rcu_barrier_func, (void *)call_rcu_func, 1); |
| 1635 | preempt_enable(); /* CPU_DYING can again fill orphan_cbs_list */ |
| 1636 | if (atomic_dec_and_test(&rcu_barrier_cpu_count)) |
| 1637 | complete(&rcu_barrier_completion); |
| 1638 | wait_for_completion(&rcu_barrier_completion); |
| 1639 | mutex_unlock(&rcu_barrier_mutex); |
| 1640 | } |
| 1641 | |
| 1642 | /** |
| 1643 | * rcu_barrier_bh - Wait until all in-flight call_rcu_bh() callbacks complete. |
| 1644 | */ |
| 1645 | void rcu_barrier_bh(void) |
| 1646 | { |
| 1647 | _rcu_barrier(&rcu_bh_state, call_rcu_bh); |
| 1648 | } |
| 1649 | EXPORT_SYMBOL_GPL(rcu_barrier_bh); |
| 1650 | |
| 1651 | /** |
| 1652 | * rcu_barrier_sched - Wait for in-flight call_rcu_sched() callbacks. |
| 1653 | */ |
| 1654 | void rcu_barrier_sched(void) |
| 1655 | { |
| 1656 | _rcu_barrier(&rcu_sched_state, call_rcu_sched); |
| 1657 | } |
| 1658 | EXPORT_SYMBOL_GPL(rcu_barrier_sched); |
| 1659 | |
| 1660 | /* |
| 1661 | * Do boot-time initialization of a CPU's per-CPU RCU data. |
| 1662 | */ |
| 1663 | static void __init |
| 1664 | rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp) |
| 1665 | { |
| 1666 | unsigned long flags; |
| 1667 | int i; |
| 1668 | struct rcu_data *rdp = rsp->rda[cpu]; |
| 1669 | struct rcu_node *rnp = rcu_get_root(rsp); |
| 1670 | |
| 1671 | /* Set up local state, ensuring consistent view of global state. */ |
| 1672 | raw_spin_lock_irqsave(&rnp->lock, flags); |
| 1673 | rdp->grpmask = 1UL << (cpu - rdp->mynode->grplo); |
| 1674 | rdp->nxtlist = NULL; |
| 1675 | for (i = 0; i < RCU_NEXT_SIZE; i++) |
| 1676 | rdp->nxttail[i] = &rdp->nxtlist; |
| 1677 | rdp->qlen = 0; |
| 1678 | #ifdef CONFIG_NO_HZ |
| 1679 | rdp->dynticks = &per_cpu(rcu_dynticks, cpu); |
| 1680 | #endif /* #ifdef CONFIG_NO_HZ */ |
| 1681 | rdp->cpu = cpu; |
| 1682 | raw_spin_unlock_irqrestore(&rnp->lock, flags); |
| 1683 | } |
| 1684 | |
| 1685 | /* |
| 1686 | * Initialize a CPU's per-CPU RCU data. Note that only one online or |
| 1687 | * offline event can be happening at a given time. Note also that we |
| 1688 | * can accept some slop in the rsp->completed access due to the fact |
| 1689 | * that this CPU cannot possibly have any RCU callbacks in flight yet. |
| 1690 | */ |
| 1691 | static void __cpuinit |
| 1692 | rcu_init_percpu_data(int cpu, struct rcu_state *rsp, int preemptable) |
| 1693 | { |
| 1694 | unsigned long flags; |
| 1695 | unsigned long mask; |
| 1696 | struct rcu_data *rdp = rsp->rda[cpu]; |
| 1697 | struct rcu_node *rnp = rcu_get_root(rsp); |
| 1698 | |
| 1699 | /* Set up local state, ensuring consistent view of global state. */ |
| 1700 | raw_spin_lock_irqsave(&rnp->lock, flags); |
| 1701 | rdp->passed_quiesc = 0; /* We could be racing with new GP, */ |
| 1702 | rdp->qs_pending = 1; /* so set up to respond to current GP. */ |
| 1703 | rdp->beenonline = 1; /* We have now been online. */ |
| 1704 | rdp->preemptable = preemptable; |
| 1705 | rdp->qlen_last_fqs_check = 0; |
| 1706 | rdp->n_force_qs_snap = rsp->n_force_qs; |
| 1707 | rdp->blimit = blimit; |
| 1708 | raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */ |
| 1709 | |
| 1710 | /* |
| 1711 | * A new grace period might start here. If so, we won't be part |
| 1712 | * of it, but that is OK, as we are currently in a quiescent state. |
| 1713 | */ |
| 1714 | |
| 1715 | /* Exclude any attempts to start a new GP on large systems. */ |
| 1716 | raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */ |
| 1717 | |
| 1718 | /* Add CPU to rcu_node bitmasks. */ |
| 1719 | rnp = rdp->mynode; |
| 1720 | mask = rdp->grpmask; |
| 1721 | do { |
| 1722 | /* Exclude any attempts to start a new GP on small systems. */ |
| 1723 | raw_spin_lock(&rnp->lock); /* irqs already disabled. */ |
| 1724 | rnp->qsmaskinit |= mask; |
| 1725 | mask = rnp->grpmask; |
| 1726 | if (rnp == rdp->mynode) { |
| 1727 | rdp->gpnum = rnp->completed; /* if GP in progress... */ |
| 1728 | rdp->completed = rnp->completed; |
| 1729 | rdp->passed_quiesc_completed = rnp->completed - 1; |
| 1730 | } |
| 1731 | raw_spin_unlock(&rnp->lock); /* irqs already disabled. */ |
| 1732 | rnp = rnp->parent; |
| 1733 | } while (rnp != NULL && !(rnp->qsmaskinit & mask)); |
| 1734 | |
| 1735 | raw_spin_unlock_irqrestore(&rsp->onofflock, flags); |
| 1736 | } |
| 1737 | |
| 1738 | static void __cpuinit rcu_online_cpu(int cpu) |
| 1739 | { |
| 1740 | rcu_init_percpu_data(cpu, &rcu_sched_state, 0); |
| 1741 | rcu_init_percpu_data(cpu, &rcu_bh_state, 0); |
| 1742 | rcu_preempt_init_percpu_data(cpu); |
| 1743 | } |
| 1744 | |
| 1745 | /* |
| 1746 | * Handle CPU online/offline notification events. |
| 1747 | */ |
| 1748 | static int __cpuinit rcu_cpu_notify(struct notifier_block *self, |
| 1749 | unsigned long action, void *hcpu) |
| 1750 | { |
| 1751 | long cpu = (long)hcpu; |
| 1752 | |
| 1753 | switch (action) { |
| 1754 | case CPU_UP_PREPARE: |
| 1755 | case CPU_UP_PREPARE_FROZEN: |
| 1756 | rcu_online_cpu(cpu); |
| 1757 | break; |
| 1758 | case CPU_DYING: |
| 1759 | case CPU_DYING_FROZEN: |
| 1760 | /* |
| 1761 | * preempt_disable() in _rcu_barrier() prevents stop_machine(), |
| 1762 | * so when "on_each_cpu(rcu_barrier_func, (void *)type, 1);" |
| 1763 | * returns, all online cpus have queued rcu_barrier_func(). |
| 1764 | * The dying CPU clears its cpu_online_mask bit and |
| 1765 | * moves all of its RCU callbacks to ->orphan_cbs_list |
| 1766 | * in the context of stop_machine(), so subsequent calls |
| 1767 | * to _rcu_barrier() will adopt these callbacks and only |
| 1768 | * then queue rcu_barrier_func() on all remaining CPUs. |
| 1769 | */ |
| 1770 | rcu_send_cbs_to_orphanage(&rcu_bh_state); |
| 1771 | rcu_send_cbs_to_orphanage(&rcu_sched_state); |
| 1772 | rcu_preempt_send_cbs_to_orphanage(); |
| 1773 | break; |
| 1774 | case CPU_DEAD: |
| 1775 | case CPU_DEAD_FROZEN: |
| 1776 | case CPU_UP_CANCELED: |
| 1777 | case CPU_UP_CANCELED_FROZEN: |
| 1778 | rcu_offline_cpu(cpu); |
| 1779 | break; |
| 1780 | default: |
| 1781 | break; |
| 1782 | } |
| 1783 | return NOTIFY_OK; |
| 1784 | } |
| 1785 | |
| 1786 | /* |
| 1787 | * Compute the per-level fanout, either using the exact fanout specified |
| 1788 | * or balancing the tree, depending on CONFIG_RCU_FANOUT_EXACT. |
| 1789 | */ |
| 1790 | #ifdef CONFIG_RCU_FANOUT_EXACT |
| 1791 | static void __init rcu_init_levelspread(struct rcu_state *rsp) |
| 1792 | { |
| 1793 | int i; |
| 1794 | |
| 1795 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) |
| 1796 | rsp->levelspread[i] = CONFIG_RCU_FANOUT; |
| 1797 | } |
| 1798 | #else /* #ifdef CONFIG_RCU_FANOUT_EXACT */ |
| 1799 | static void __init rcu_init_levelspread(struct rcu_state *rsp) |
| 1800 | { |
| 1801 | int ccur; |
| 1802 | int cprv; |
| 1803 | int i; |
| 1804 | |
| 1805 | cprv = NR_CPUS; |
| 1806 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { |
| 1807 | ccur = rsp->levelcnt[i]; |
| 1808 | rsp->levelspread[i] = (cprv + ccur - 1) / ccur; |
| 1809 | cprv = ccur; |
| 1810 | } |
| 1811 | } |
| 1812 | #endif /* #else #ifdef CONFIG_RCU_FANOUT_EXACT */ |
| 1813 | |
| 1814 | /* |
| 1815 | * Helper function for rcu_init() that initializes one rcu_state structure. |
| 1816 | */ |
| 1817 | static void __init rcu_init_one(struct rcu_state *rsp) |
| 1818 | { |
| 1819 | static char *buf[] = { "rcu_node_level_0", |
| 1820 | "rcu_node_level_1", |
| 1821 | "rcu_node_level_2", |
| 1822 | "rcu_node_level_3" }; /* Match MAX_RCU_LVLS */ |
| 1823 | int cpustride = 1; |
| 1824 | int i; |
| 1825 | int j; |
| 1826 | struct rcu_node *rnp; |
| 1827 | |
| 1828 | BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ |
| 1829 | |
| 1830 | /* Initialize the level-tracking arrays. */ |
| 1831 | |
| 1832 | for (i = 1; i < NUM_RCU_LVLS; i++) |
| 1833 | rsp->level[i] = rsp->level[i - 1] + rsp->levelcnt[i - 1]; |
| 1834 | rcu_init_levelspread(rsp); |
| 1835 | |
| 1836 | /* Initialize the elements themselves, starting from the leaves. */ |
| 1837 | |
| 1838 | for (i = NUM_RCU_LVLS - 1; i >= 0; i--) { |
| 1839 | cpustride *= rsp->levelspread[i]; |
| 1840 | rnp = rsp->level[i]; |
| 1841 | for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) { |
| 1842 | raw_spin_lock_init(&rnp->lock); |
| 1843 | lockdep_set_class_and_name(&rnp->lock, |
| 1844 | &rcu_node_class[i], buf[i]); |
| 1845 | rnp->gpnum = 0; |
| 1846 | rnp->qsmask = 0; |
| 1847 | rnp->qsmaskinit = 0; |
| 1848 | rnp->grplo = j * cpustride; |
| 1849 | rnp->grphi = (j + 1) * cpustride - 1; |
| 1850 | if (rnp->grphi >= NR_CPUS) |
| 1851 | rnp->grphi = NR_CPUS - 1; |
| 1852 | if (i == 0) { |
| 1853 | rnp->grpnum = 0; |
| 1854 | rnp->grpmask = 0; |
| 1855 | rnp->parent = NULL; |
| 1856 | } else { |
| 1857 | rnp->grpnum = j % rsp->levelspread[i - 1]; |
| 1858 | rnp->grpmask = 1UL << rnp->grpnum; |
| 1859 | rnp->parent = rsp->level[i - 1] + |
| 1860 | j / rsp->levelspread[i - 1]; |
| 1861 | } |
| 1862 | rnp->level = i; |
| 1863 | INIT_LIST_HEAD(&rnp->blocked_tasks[0]); |
| 1864 | INIT_LIST_HEAD(&rnp->blocked_tasks[1]); |
| 1865 | INIT_LIST_HEAD(&rnp->blocked_tasks[2]); |
| 1866 | INIT_LIST_HEAD(&rnp->blocked_tasks[3]); |
| 1867 | } |
| 1868 | } |
| 1869 | |
| 1870 | rnp = rsp->level[NUM_RCU_LVLS - 1]; |
| 1871 | for_each_possible_cpu(i) { |
| 1872 | if (i > rnp->grphi) |
| 1873 | rnp++; |
| 1874 | rsp->rda[i]->mynode = rnp; |
| 1875 | rcu_boot_init_percpu_data(i, rsp); |
| 1876 | } |
| 1877 | } |
| 1878 | |
| 1879 | /* |
| 1880 | * Helper macro for __rcu_init() and __rcu_init_preempt(). To be used |
| 1881 | * nowhere else! Assigns leaf node pointers into each CPU's rcu_data |
| 1882 | * structure. |
| 1883 | */ |
| 1884 | #define RCU_INIT_FLAVOR(rsp, rcu_data) \ |
| 1885 | do { \ |
| 1886 | int i; \ |
| 1887 | \ |
| 1888 | for_each_possible_cpu(i) { \ |
| 1889 | (rsp)->rda[i] = &per_cpu(rcu_data, i); \ |
| 1890 | } \ |
| 1891 | rcu_init_one(rsp); \ |
| 1892 | } while (0) |
| 1893 | |
| 1894 | void __init rcu_init(void) |
| 1895 | { |
| 1896 | int cpu; |
| 1897 | |
| 1898 | rcu_bootup_announce(); |
| 1899 | #ifdef CONFIG_RCU_CPU_STALL_DETECTOR |
| 1900 | printk(KERN_INFO "RCU-based detection of stalled CPUs is enabled.\n"); |
| 1901 | #endif /* #ifdef CONFIG_RCU_CPU_STALL_DETECTOR */ |
| 1902 | #if NUM_RCU_LVL_4 != 0 |
| 1903 | printk(KERN_INFO "Experimental four-level hierarchy is enabled.\n"); |
| 1904 | #endif /* #if NUM_RCU_LVL_4 != 0 */ |
| 1905 | RCU_INIT_FLAVOR(&rcu_sched_state, rcu_sched_data); |
| 1906 | RCU_INIT_FLAVOR(&rcu_bh_state, rcu_bh_data); |
| 1907 | __rcu_init_preempt(); |
| 1908 | open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); |
| 1909 | |
| 1910 | /* |
| 1911 | * We don't need protection against CPU-hotplug here because |
| 1912 | * this is called early in boot, before either interrupts |
| 1913 | * or the scheduler are operational. |
| 1914 | */ |
| 1915 | cpu_notifier(rcu_cpu_notify, 0); |
| 1916 | for_each_online_cpu(cpu) |
| 1917 | rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu); |
| 1918 | } |
| 1919 | |
| 1920 | #include "rcutree_plugin.h" |