arch/powerpc/platforms/cell/spufs/sched.c

   1 /* sched.c - SPU scheduler.
   2  *
   3  * Copyright (C) IBM 2005
   4  * Author: Mark Nutter <mnutter@us.ibm.com>
   5  *
   6  * 2006-03-31   NUMA domains added.
   7  *
   8  * This program is free software; you can redistribute it and/or modify
   9  * it under the terms of the GNU General Public License as published by
  10  * the Free Software Foundation; either version 2, or (at your option)
  11  * any later version.
  12  *
  13  * This program is distributed in the hope that it will be useful,
  14  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  15  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  16  * GNU General Public License for more details.
  17  *
  18  * You should have received a copy of the GNU General Public License
  19  * along with this program; if not, write to the Free Software
  20  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  21  */
  22
  23 #undef DEBUG
  24
  25 #include <linux/module.h>
  26 #include <linux/errno.h>
  27 #include <linux/sched.h>
  28 #include <linux/kernel.h>
  29 #include <linux/mm.h>
  30 #include <linux/completion.h>
  31 #include <linux/vmalloc.h>
  32 #include <linux/smp.h>
  33 #include <linux/stddef.h>
  34 #include <linux/unistd.h>
  35 #include <linux/numa.h>
  36 #include <linux/mutex.h>
  37 #include <linux/notifier.h>
  38
  39 #include <asm/io.h>
  40 #include <asm/mmu_context.h>
  41 #include <asm/spu.h>
  42 #include <asm/spu_csa.h>
  43 #include <asm/spu_priv1.h>
  44 #include "spufs.h"
  45
  46 #define SPU_TIMESLICE   (HZ)
  47
  48 struct spu_prio_array {
  49         DECLARE_BITMAP(bitmap, MAX_PRIO);
  50         struct list_head runq[MAX_PRIO];
  51         spinlock_t runq_lock;
  52         struct list_head active_list[MAX_NUMNODES];
  53         struct mutex active_mutex[MAX_NUMNODES];
  54 };
  55
  56 static struct spu_prio_array *spu_prio;
  57 static struct workqueue_struct *spu_sched_wq;
  58
  59 static inline int node_allowed(int node)
  60 {
  61         cpumask_t mask;
  62
  63         if (!nr_cpus_node(node))
  64                 return 0;
  65         mask = node_to_cpumask(node);
  66         if (!cpus_intersects(mask, current->cpus_allowed))
  67                 return 0;
  68         return 1;
  69 }
  70
  71 void spu_start_tick(struct spu_context *ctx)
  72 {
  73         if (ctx->policy == SCHED_RR) {
  74                 /*
  75                  * Make sure the exiting bit is cleared.
  76                  */
  77                 clear_bit(SPU_SCHED_EXITING, &ctx->sched_flags);
  78                 mb();
  79                 queue_delayed_work(spu_sched_wq, &ctx->sched_work, SPU_TIMESLICE);
  80         }
  81 }
  82
  83 void spu_stop_tick(struct spu_context *ctx)
  84 {
  85         if (ctx->policy == SCHED_RR) {
  86                 /*
  87                  * While the work can be rearming normally setting this flag
  88                  * makes sure it does not rearm itself anymore.
  89                  */
  90                 set_bit(SPU_SCHED_EXITING, &ctx->sched_flags);
  91                 mb();
  92                 cancel_delayed_work(&ctx->sched_work);
  93         }
  94 }
  95
  96 /**
  97  * spu_add_to_active_list - add spu to active list
  98  * @spu:        spu to add to the active list
  99  */
 100 static void spu_add_to_active_list(struct spu *spu)
 101 {
 102         mutex_lock(&spu_prio->active_mutex[spu->node]);
 103         list_add_tail(&spu->list, &spu_prio->active_list[spu->node]);
 104         mutex_unlock(&spu_prio->active_mutex[spu->node]);
 105 }
 106
 107 /**
 108  * spu_remove_from_active_list - remove spu from active list
 109  * @spu:       spu to remove from the active list
 110  */
 111 static void spu_remove_from_active_list(struct spu *spu)
 112 {
 113         int node = spu->node;
 114
 115         mutex_lock(&spu_prio->active_mutex[node]);
 116         list_del_init(&spu->list);
 117         mutex_unlock(&spu_prio->active_mutex[node]);
 118 }
 119
 120 static BLOCKING_NOTIFIER_HEAD(spu_switch_notifier);
 121
 122 static void spu_switch_notify(struct spu *spu, struct spu_context *ctx)
 123 {
 124         blocking_notifier_call_chain(&spu_switch_notifier,
 125                             ctx ? ctx->object_id : 0, spu);
 126 }
 127
 128 int spu_switch_event_register(struct notifier_block * n)
 129 {
 130         return blocking_notifier_chain_register(&spu_switch_notifier, n);
 131 }
 132
 133 int spu_switch_event_unregister(struct notifier_block * n)
 134 {
 135         return blocking_notifier_chain_unregister(&spu_switch_notifier, n);
 136 }
 137
 138 /**
 139  * spu_bind_context - bind spu context to physical spu
 140  * @spu:        physical spu to bind to
 141  * @ctx:        context to bind
 142  */
 143 static void spu_bind_context(struct spu *spu, struct spu_context *ctx)
 144 {
 145         pr_debug("%s: pid=%d SPU=%d NODE=%d\n", __FUNCTION__, current->pid,
 146                  spu->number, spu->node);
 147         spu->ctx = ctx;
 148         spu->flags = 0;
 149         ctx->spu = spu;
 150         ctx->ops = &spu_hw_ops;
 151         spu->pid = current->pid;
 152         spu_associate_mm(spu, ctx->owner);
 153         spu->ibox_callback = spufs_ibox_callback;
 154         spu->wbox_callback = spufs_wbox_callback;
 155         spu->stop_callback = spufs_stop_callback;
 156         spu->mfc_callback = spufs_mfc_callback;
 157         spu->dma_callback = spufs_dma_callback;
 158         mb();
 159         spu_unmap_mappings(ctx);
 160         spu_restore(&ctx->csa, spu);
 161         spu->timestamp = jiffies;
 162         spu_cpu_affinity_set(spu, raw_smp_processor_id());
 163         spu_switch_notify(spu, ctx);
 164         spu_add_to_active_list(spu);
 165         ctx->state = SPU_STATE_RUNNABLE;
 166 }
 167
 168 /**
 169  * spu_unbind_context - unbind spu context from physical spu
 170  * @spu:        physical spu to unbind from
 171  * @ctx:        context to unbind
 172  */
 173 static void spu_unbind_context(struct spu *spu, struct spu_context *ctx)
 174 {
 175         pr_debug("%s: unbind pid=%d SPU=%d NODE=%d\n", __FUNCTION__,
 176                  spu->pid, spu->number, spu->node);
 177
 178         spu_remove_from_active_list(spu);
 179         spu_switch_notify(spu, NULL);
 180         spu_unmap_mappings(ctx);
 181         spu_save(&ctx->csa, spu);
 182         spu->timestamp = jiffies;
 183         ctx->state = SPU_STATE_SAVED;
 184         spu->ibox_callback = NULL;
 185         spu->wbox_callback = NULL;
 186         spu->stop_callback = NULL;
 187         spu->mfc_callback = NULL;
 188         spu->dma_callback = NULL;
 189         spu_associate_mm(spu, NULL);
 190         spu->pid = 0;
 191         ctx->ops = &spu_backing_ops;
 192         ctx->spu = NULL;
 193         spu->flags = 0;
 194         spu->ctx = NULL;
 195 }
 196
 197 /**
 198  * spu_add_to_rq - add a context to the runqueue
 199  * @ctx:       context to add
 200  */
 201 static void __spu_add_to_rq(struct spu_context *ctx)
 202 {
 203         int prio = ctx->prio;
 204
 205         list_add_tail(&ctx->rq, &spu_prio->runq[prio]);
 206         set_bit(prio, spu_prio->bitmap);
 207 }
 208
 209 static void __spu_del_from_rq(struct spu_context *ctx)
 210 {
 211         int prio = ctx->prio;
 212
 213         if (!list_empty(&ctx->rq))
 214                 list_del_init(&ctx->rq);
 215         if (list_empty(&spu_prio->runq[prio]))
 216                 clear_bit(prio, spu_prio->bitmap);
 217 }
 218
 219 static void spu_prio_wait(struct spu_context *ctx)
 220 {
 221         DEFINE_WAIT(wait);
 222
 223         spin_lock(&spu_prio->runq_lock);
 224         prepare_to_wait_exclusive(&ctx->stop_wq, &wait, TASK_INTERRUPTIBLE);
 225         if (!signal_pending(current)) {
 226                 __spu_add_to_rq(ctx);
 227                 spin_unlock(&spu_prio->runq_lock);
 228                 mutex_unlock(&ctx->state_mutex);
 229                 schedule();
 230                 mutex_lock(&ctx->state_mutex);
 231                 spin_lock(&spu_prio->runq_lock);
 232                 __spu_del_from_rq(ctx);
 233         }
 234         spin_unlock(&spu_prio->runq_lock);
 235         __set_current_state(TASK_RUNNING);
 236         remove_wait_queue(&ctx->stop_wq, &wait);
 237 }
 238
 239 static struct spu *spu_get_idle(struct spu_context *ctx)
 240 {
 241         struct spu *spu = NULL;
 242         int node = cpu_to_node(raw_smp_processor_id());
 243         int n;
 244
 245         for (n = 0; n < MAX_NUMNODES; n++, node++) {
 246                 node = (node < MAX_NUMNODES) ? node : 0;
 247                 if (!node_allowed(node))
 248                         continue;
 249                 spu = spu_alloc_node(node);
 250                 if (spu)
 251                         break;
 252         }
 253         return spu;
 254 }
 255
 256 /**
 257  * find_victim - find a lower priority context to preempt
 258  * @ctx:        canidate context for running
 259  *
 260  * Returns the freed physical spu to run the new context on.
 261  */
 262 static struct spu *find_victim(struct spu_context *ctx)
 263 {
 264         struct spu_context *victim = NULL;
 265         struct spu *spu;
 266         int node, n;
 267
 268         /*
 269          * Look for a possible preemption candidate on the local node first.
 270          * If there is no candidate look at the other nodes.  This isn't
 271          * exactly fair, but so far the whole spu schedule tries to keep
 272          * a strong node affinity.  We might want to fine-tune this in
 273          * the future.
 274          */
 275  restart:
 276         node = cpu_to_node(raw_smp_processor_id());
 277         for (n = 0; n < MAX_NUMNODES; n++, node++) {
 278                 node = (node < MAX_NUMNODES) ? node : 0;
 279                 if (!node_allowed(node))
 280                         continue;
 281
 282                 mutex_lock(&spu_prio->active_mutex[node]);
 283                 list_for_each_entry(spu, &spu_prio->active_list[node], list) {
 284                         struct spu_context *tmp = spu->ctx;
 285
 286                         if (tmp->rt_priority < ctx->rt_priority &&
 287                             (!victim || tmp->rt_priority < victim->rt_priority))
 288                                 victim = spu->ctx;
 289                 }
 290                 mutex_unlock(&spu_prio->active_mutex[node]);
 291
 292                 if (victim) {
 293                         /*
 294                          * This nests ctx->state_mutex, but we always lock
 295                          * higher priority contexts before lower priority
 296                          * ones, so this is safe until we introduce
 297                          * priority inheritance schemes.
 298                          */
 299                         if (!mutex_trylock(&victim->state_mutex)) {
 300                                 victim = NULL;
 301                                 goto restart;
 302                         }
 303
 304                         spu = victim->spu;
 305                         if (!spu) {
 306                                 /*
 307                                  * This race can happen because we've dropped
 308                                  * the active list mutex.  No a problem, just
 309                                  * restart the search.
 310                                  */
 311                                 mutex_unlock(&victim->state_mutex);
 312                                 victim = NULL;
 313                                 goto restart;
 314                         }
 315                         spu_unbind_context(spu, victim);
 316                         mutex_unlock(&victim->state_mutex);
 317                         /*
 318                          * We need to break out of the wait loop in spu_run
 319                          * manually to ensure this context gets put on the
 320                          * runqueue again ASAP.
 321                          */
 322                         wake_up(&victim->stop_wq);
 323                         return spu;
 324                 }
 325         }
 326
 327         return NULL;
 328 }
 329
 330 /**
 331  * spu_activate - find a free spu for a context and execute it
 332  * @ctx:        spu context to schedule
 333  * @flags:      flags (currently ignored)
 334  *
 335  * Tries to find a free spu to run @ctx.  If no free spu is available
 336  * add the context to the runqueue so it gets woken up once an spu
 337  * is available.
 338  */
 339 int spu_activate(struct spu_context *ctx, unsigned long flags)
 340 {
 341
 342         if (ctx->spu)
 343                 return 0;
 344
 345         do {
 346                 struct spu *spu;
 347
 348                 spu = spu_get_idle(ctx);
 349                 /*
 350                  * If this is a realtime thread we try to get it running by
 351                  * preempting a lower priority thread.
 352                  */
 353                 if (!spu && ctx->rt_priority)
 354                         spu = find_victim(ctx);
 355                 if (spu) {
 356                         spu_bind_context(spu, ctx);
 357                         return 0;
 358                 }
 359
 360                 spu_prio_wait(ctx);
 361         } while (!signal_pending(current));
 362
 363         return -ERESTARTSYS;
 364 }
 365
 366 /**
 367  * grab_runnable_context - try to find a runnable context
 368  *
 369  * Remove the highest priority context on the runqueue and return it
 370  * to the caller.  Returns %NULL if no runnable context was found.
 371  */
 372 static struct spu_context *grab_runnable_context(int prio)
 373 {
 374         struct spu_context *ctx = NULL;
 375         int best;
 376
 377         spin_lock(&spu_prio->runq_lock);
 378         best = sched_find_first_bit(spu_prio->bitmap);
 379         if (best < prio) {
 380                 struct list_head *rq = &spu_prio->runq[best];
 381
 382                 BUG_ON(list_empty(rq));
 383
 384                 ctx = list_entry(rq->next, struct spu_context, rq);
 385                 __spu_del_from_rq(ctx);
 386         }
 387         spin_unlock(&spu_prio->runq_lock);
 388
 389         return ctx;
 390 }
 391
 392 static int __spu_deactivate(struct spu_context *ctx, int force, int max_prio)
 393 {
 394         struct spu *spu = ctx->spu;
 395         struct spu_context *new = NULL;
 396
 397         if (spu) {
 398                 new = grab_runnable_context(max_prio);
 399                 if (new || force) {
 400                         spu_unbind_context(spu, ctx);
 401                         spu_free(spu);
 402                         if (new)
 403                                 wake_up(&new->stop_wq);
 404                 }
 405
 406         }
 407
 408         return new != NULL;
 409 }
 410
 411 /**
 412  * spu_deactivate - unbind a context from it's physical spu
 413  * @ctx:        spu context to unbind
 414  *
 415  * Unbind @ctx from the physical spu it is running on and schedule
 416  * the highest priority context to run on the freed physical spu.
 417  */
 418 void spu_deactivate(struct spu_context *ctx)
 419 {
 420         __spu_deactivate(ctx, 1, MAX_PRIO);
 421 }
 422
 423 /**
 424  * spu_yield -  yield a physical spu if others are waiting
 425  * @ctx:        spu context to yield
 426  *
 427  * Check if there is a higher priority context waiting and if yes
 428  * unbind @ctx from the physical spu and schedule the highest
 429  * priority context to run on the freed physical spu instead.
 430  */
 431 void spu_yield(struct spu_context *ctx)
 432 {
 433         if (!(ctx->flags & SPU_CREATE_NOSCHED)) {
 434                 mutex_lock(&ctx->state_mutex);
 435                 __spu_deactivate(ctx, 0, MAX_PRIO);
 436                 mutex_unlock(&ctx->state_mutex);
 437         }
 438 }
 439
 440 void spu_sched_tick(struct work_struct *work)
 441 {
 442         struct spu_context *ctx =
 443                 container_of(work, struct spu_context, sched_work.work);
 444         int preempted;
 445
 446         /*
 447          * If this context is being stopped avoid rescheduling from the
 448          * scheduler tick because we would block on the state_mutex.
 449          * The caller will yield the spu later on anyway.
 450          */
 451         if (test_bit(SPU_SCHED_EXITING, &ctx->sched_flags))
 452                 return;
 453
 454         mutex_lock(&ctx->state_mutex);
 455         preempted = __spu_deactivate(ctx, 0, ctx->prio + 1);
 456         mutex_unlock(&ctx->state_mutex);
 457
 458         if (preempted) {
 459                 /*
 460                  * We need to break out of the wait loop in spu_run manually
 461                  * to ensure this context gets put on the runqueue again
 462                  * ASAP.
 463                  */
 464                 wake_up(&ctx->stop_wq);
 465         } else {
 466                 spu_start_tick(ctx);
 467         }
 468 }
 469
 470 int __init spu_sched_init(void)
 471 {
 472         int i;
 473
 474         spu_sched_wq = create_singlethread_workqueue("spusched");
 475         if (!spu_sched_wq)
 476                 return 1;
 477
 478         spu_prio = kzalloc(sizeof(struct spu_prio_array), GFP_KERNEL);
 479         if (!spu_prio) {
 480                 printk(KERN_WARNING "%s: Unable to allocate priority queue.\n",
 481                        __FUNCTION__);
 482                        destroy_workqueue(spu_sched_wq);
 483                 return 1;
 484         }
 485         for (i = 0; i < MAX_PRIO; i++) {
 486                 INIT_LIST_HEAD(&spu_prio->runq[i]);
 487                 __clear_bit(i, spu_prio->bitmap);
 488         }
 489         __set_bit(MAX_PRIO, spu_prio->bitmap);
 490         for (i = 0; i < MAX_NUMNODES; i++) {
 491                 mutex_init(&spu_prio->active_mutex[i]);
 492                 INIT_LIST_HEAD(&spu_prio->active_list[i]);
 493         }
 494         spin_lock_init(&spu_prio->runq_lock);
 495         return 0;
 496 }
 497
 498 void __exit spu_sched_exit(void)
 499 {
 500         struct spu *spu, *tmp;
 501         int node;
 502
 503         for (node = 0; node < MAX_NUMNODES; node++) {
 504                 mutex_lock(&spu_prio->active_mutex[node]);
 505                 list_for_each_entry_safe(spu, tmp, &spu_prio->active_list[node],
 506                                          list) {
 507                         list_del_init(&spu->list);
 508                         spu_free(spu);
 509                 }
 510                 mutex_unlock(&spu_prio->active_mutex[node]);
 511         }
 512         kfree(spu_prio);
 513         destroy_workqueue(spu_sched_wq);
 514 }