#include <linux/prefetch.h>
#include <linux/delay.h>
#include <linux/stop_machine.h>
+#include <linux/random.h>
#include "rcutree.h"
#include <trace/events/rcu.h>
/* Data structures. */
static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
+static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
#define RCU_STATE_INITIALIZER(sname, cr) { \
.level = { &sname##_state.node[0] }, \
.orphan_nxttail = &sname##_state.orphan_nxtlist, \
.orphan_donetail = &sname##_state.orphan_donelist, \
.barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
- .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&sname##_state.fqslock), \
.name = #sname, \
}
/* Increase (but not decrease) the CONFIG_RCU_FANOUT_LEAF at boot time. */
static int rcu_fanout_leaf = CONFIG_RCU_FANOUT_LEAF;
-module_param(rcu_fanout_leaf, int, 0);
+module_param(rcu_fanout_leaf, int, 0444);
int rcu_num_lvls __read_mostly = RCU_NUM_LVLS;
static int num_rcu_lvl[] = { /* Number of rcu_nodes at specified level. */
NUM_RCU_LVL_0,
{
struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu);
- rdp->passed_quiesce_gpnum = rdp->gpnum;
- barrier();
if (rdp->passed_quiesce == 0)
trace_rcu_grace_period("rcu_sched", rdp->gpnum, "cpuqs");
rdp->passed_quiesce = 1;
{
struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
- rdp->passed_quiesce_gpnum = rdp->gpnum;
- barrier();
if (rdp->passed_quiesce == 0)
trace_rcu_grace_period("rcu_bh", rdp->gpnum, "cpuqs");
rdp->passed_quiesce = 1;
static int qhimark = 10000; /* If this many pending, ignore blimit. */
static int qlowmark = 100; /* Once only this many pending, use blimit. */
-module_param(blimit, int, 0);
-module_param(qhimark, int, 0);
-module_param(qlowmark, int, 0);
+module_param(blimit, int, 0444);
+module_param(qhimark, int, 0444);
+module_param(qlowmark, int, 0444);
int rcu_cpu_stall_suppress __read_mostly; /* 1 = suppress stall warnings. */
int rcu_cpu_stall_timeout __read_mostly = CONFIG_RCU_CPU_STALL_TIMEOUT;
module_param(rcu_cpu_stall_suppress, int, 0644);
module_param(rcu_cpu_stall_timeout, int, 0644);
-static void force_quiescent_state(struct rcu_state *rsp, int relaxed);
+static ulong jiffies_till_first_fqs = RCU_JIFFIES_TILL_FORCE_QS;
+static ulong jiffies_till_next_fqs = RCU_JIFFIES_TILL_FORCE_QS;
+
+module_param(jiffies_till_first_fqs, ulong, 0644);
+module_param(jiffies_till_next_fqs, ulong, 0644);
+
+static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *));
+static void force_quiescent_state(struct rcu_state *rsp);
static int rcu_pending(int cpu);
/*
*/
void rcu_bh_force_quiescent_state(void)
{
- force_quiescent_state(&rcu_bh_state, 0);
+ force_quiescent_state(&rcu_bh_state);
}
EXPORT_SYMBOL_GPL(rcu_bh_force_quiescent_state);
*/
void rcu_sched_force_quiescent_state(void)
{
- force_quiescent_state(&rcu_sched_state, 0);
+ force_quiescent_state(&rcu_sched_state);
}
EXPORT_SYMBOL_GPL(rcu_sched_force_quiescent_state);
static int
cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
{
- return *rdp->nxttail[RCU_DONE_TAIL] && !rcu_gp_in_progress(rsp);
+ return *rdp->nxttail[RCU_DONE_TAIL +
+ ACCESS_ONCE(rsp->completed) != rdp->completed] &&
+ !rcu_gp_in_progress(rsp);
}
/*
else if (!trigger_all_cpu_backtrace())
dump_stack();
- /* If so configured, complain about tasks blocking the grace period. */
+ /* Complain about tasks blocking the grace period. */
rcu_print_detail_task_stall(rsp);
- force_quiescent_state(rsp, 0); /* Kick them all. */
+ force_quiescent_state(rsp); /* Kick them all. */
}
static void print_cpu_stall(struct rcu_state *rsp)
*/
rdp->gpnum = rnp->gpnum;
trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpustart");
- if (rnp->qsmask & rdp->grpmask) {
- rdp->qs_pending = 1;
- rdp->passed_quiesce = 0;
- } else {
- rdp->qs_pending = 0;
- }
+ rdp->passed_quiesce = 0;
+ rdp->qs_pending = !!(rnp->qsmask & rdp->grpmask);
zero_cpu_stall_ticks(rdp);
}
}
* our behalf. Catch up with this state to avoid noting
* spurious new grace periods. If another grace period
* has started, then rnp->gpnum will have advanced, so
- * we will detect this later on.
+ * we will detect this later on. Of course, any quiescent
+ * states we found for the old GP are now invalid.
*/
- if (ULONG_CMP_LT(rdp->gpnum, rdp->completed))
+ if (ULONG_CMP_LT(rdp->gpnum, rdp->completed)) {
rdp->gpnum = rdp->completed;
+ rdp->passed_quiesce = 0;
+ }
/*
* If RCU does not need a quiescent state from this CPU,
/* Prior grace period ended, so advance callbacks for current CPU. */
__rcu_process_gp_end(rsp, rnp, rdp);
- /*
- * Because this CPU just now started the new grace period, we know
- * that all of its callbacks will be covered by this upcoming grace
- * period, even the ones that were registered arbitrarily recently.
- * Therefore, advance all outstanding callbacks to RCU_WAIT_TAIL.
- *
- * Other CPUs cannot be sure exactly when the grace period started.
- * Therefore, their recently registered callbacks must pass through
- * an additional RCU_NEXT_READY stage, so that they will be handled
- * by the next RCU grace period.
- */
- rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
- rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
-
/* Set state so that this CPU will detect the next quiescent state. */
__note_new_gpnum(rsp, rnp, rdp);
}
/*
- * Start a new RCU grace period if warranted, re-initializing the hierarchy
- * in preparation for detecting the next grace period. The caller must hold
- * the root node's ->lock, which is released before return. Hard irqs must
- * be disabled.
- *
- * Note that it is legal for a dying CPU (which is marked as offline) to
- * invoke this function. This can happen when the dying CPU reports its
- * quiescent state.
+ * Initialize a new grace period.
*/
-static void
-rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
- __releases(rcu_get_root(rsp)->lock)
+static int rcu_gp_init(struct rcu_state *rsp)
{
- struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
+ struct rcu_data *rdp;
struct rcu_node *rnp = rcu_get_root(rsp);
- if (!rcu_scheduler_fully_active ||
- !cpu_needs_another_gp(rsp, rdp)) {
- /*
- * Either the scheduler hasn't yet spawned the first
- * non-idle task or this CPU does not need another
- * grace period. Either way, don't start a new grace
- * period.
- */
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- return;
- }
+ raw_spin_lock_irq(&rnp->lock);
+ rsp->gp_flags = 0; /* Clear all flags: New grace period. */
- if (rsp->fqs_active) {
- /*
- * This CPU needs a grace period, but force_quiescent_state()
- * is running. Tell it to start one on this CPU's behalf.
- */
- rsp->fqs_need_gp = 1;
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- return;
+ if (rcu_gp_in_progress(rsp)) {
+ /* Grace period already in progress, don't start another. */
+ raw_spin_unlock_irq(&rnp->lock);
+ return 0;
}
/* Advance to a new grace period and initialize state. */
rsp->gpnum++;
trace_rcu_grace_period(rsp->name, rsp->gpnum, "start");
- WARN_ON_ONCE(rsp->fqs_state == RCU_GP_INIT);
- rsp->fqs_state = RCU_GP_INIT; /* Hold off force_quiescent_state. */
- rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
record_gp_stall_check_time(rsp);
- raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */
+ raw_spin_unlock_irq(&rnp->lock);
/* Exclude any concurrent CPU-hotplug operations. */
- raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */
+ get_online_cpus();
/*
* Set the quiescent-state-needed bits in all the rcu_node
- * structures for all currently online CPUs in breadth-first
- * order, starting from the root rcu_node structure. This
- * operation relies on the layout of the hierarchy within the
- * rsp->node[] array. Note that other CPUs will access only
- * the leaves of the hierarchy, which still indicate that no
+ * structures for all currently online CPUs in breadth-first order,
+ * starting from the root rcu_node structure, relying on the layout
+ * of the tree within the rsp->node[] array. Note that other CPUs
+ * will access only the leaves of the hierarchy, thus seeing that no
* grace period is in progress, at least until the corresponding
* leaf node has been initialized. In addition, we have excluded
* CPU-hotplug operations.
*
- * Note that the grace period cannot complete until we finish
- * the initialization process, as there will be at least one
- * qsmask bit set in the root node until that time, namely the
- * one corresponding to this CPU, due to the fact that we have
- * irqs disabled.
+ * The grace period cannot complete until the initialization
+ * process finishes, because this kthread handles both.
*/
rcu_for_each_node_breadth_first(rsp, rnp) {
- raw_spin_lock(&rnp->lock); /* irqs already disabled. */
+ raw_spin_lock_irq(&rnp->lock);
+ rdp = this_cpu_ptr(rsp->rda);
rcu_preempt_check_blocked_tasks(rnp);
rnp->qsmask = rnp->qsmaskinit;
rnp->gpnum = rsp->gpnum;
+ WARN_ON_ONCE(rnp->completed != rsp->completed);
rnp->completed = rsp->completed;
if (rnp == rdp->mynode)
rcu_start_gp_per_cpu(rsp, rnp, rdp);
trace_rcu_grace_period_init(rsp->name, rnp->gpnum,
rnp->level, rnp->grplo,
rnp->grphi, rnp->qsmask);
- raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
+ raw_spin_unlock_irq(&rnp->lock);
+#ifdef CONFIG_PROVE_RCU_DELAY
+ if ((random32() % (rcu_num_nodes * 8)) == 0)
+ schedule_timeout_uninterruptible(2);
+#endif /* #ifdef CONFIG_PROVE_RCU_DELAY */
+ cond_resched();
}
- rnp = rcu_get_root(rsp);
- raw_spin_lock(&rnp->lock); /* irqs already disabled. */
- rsp->fqs_state = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */
- raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
- raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
+ put_online_cpus();
+ return 1;
}
/*
- * Report a full set of quiescent states to the specified rcu_state
- * data structure. This involves cleaning up after the prior grace
- * period and letting rcu_start_gp() start up the next grace period
- * if one is needed. Note that the caller must hold rnp->lock, as
- * required by rcu_start_gp(), which will release it.
+ * Do one round of quiescent-state forcing.
*/
-static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
- __releases(rcu_get_root(rsp)->lock)
+int rcu_gp_fqs(struct rcu_state *rsp, int fqs_state_in)
{
- unsigned long gp_duration;
+ int fqs_state = fqs_state_in;
struct rcu_node *rnp = rcu_get_root(rsp);
- struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
- WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
+ rsp->n_force_qs++;
+ if (fqs_state == RCU_SAVE_DYNTICK) {
+ /* Collect dyntick-idle snapshots. */
+ force_qs_rnp(rsp, dyntick_save_progress_counter);
+ fqs_state = RCU_FORCE_QS;
+ } else {
+ /* Handle dyntick-idle and offline CPUs. */
+ force_qs_rnp(rsp, rcu_implicit_dynticks_qs);
+ }
+ /* Clear flag to prevent immediate re-entry. */
+ if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
+ raw_spin_lock_irq(&rnp->lock);
+ rsp->gp_flags &= ~RCU_GP_FLAG_FQS;
+ raw_spin_unlock_irq(&rnp->lock);
+ }
+ return fqs_state;
+}
- /*
- * Ensure that all grace-period and pre-grace-period activity
- * is seen before the assignment to rsp->completed.
- */
- smp_mb(); /* See above block comment. */
+/*
+ * Clean up after the old grace period.
+ */
+static void rcu_gp_cleanup(struct rcu_state *rsp)
+{
+ unsigned long gp_duration;
+ struct rcu_data *rdp;
+ struct rcu_node *rnp = rcu_get_root(rsp);
+
+ raw_spin_lock_irq(&rnp->lock);
gp_duration = jiffies - rsp->gp_start;
if (gp_duration > rsp->gp_max)
rsp->gp_max = gp_duration;
* they can do to advance the grace period. It is therefore
* safe for us to drop the lock in order to mark the grace
* period as completed in all of the rcu_node structures.
- *
- * But if this CPU needs another grace period, it will take
- * care of this while initializing the next grace period.
- * We use RCU_WAIT_TAIL instead of the usual RCU_DONE_TAIL
- * because the callbacks have not yet been advanced: Those
- * callbacks are waiting on the grace period that just now
- * completed.
*/
- if (*rdp->nxttail[RCU_WAIT_TAIL] == NULL) {
- raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
+ raw_spin_unlock_irq(&rnp->lock);
- /*
- * Propagate new ->completed value to rcu_node structures
- * so that other CPUs don't have to wait until the start
- * of the next grace period to process their callbacks.
- */
- rcu_for_each_node_breadth_first(rsp, rnp) {
- raw_spin_lock(&rnp->lock); /* irqs already disabled. */
- rnp->completed = rsp->gpnum;
- raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
- }
- rnp = rcu_get_root(rsp);
- raw_spin_lock(&rnp->lock); /* irqs already disabled. */
+ /*
+ * Propagate new ->completed value to rcu_node structures so
+ * that other CPUs don't have to wait until the start of the next
+ * grace period to process their callbacks. This also avoids
+ * some nasty RCU grace-period initialization races by forcing
+ * the end of the current grace period to be completely recorded in
+ * all of the rcu_node structures before the beginning of the next
+ * grace period is recorded in any of the rcu_node structures.
+ */
+ rcu_for_each_node_breadth_first(rsp, rnp) {
+ raw_spin_lock_irq(&rnp->lock);
+ rnp->completed = rsp->gpnum;
+ raw_spin_unlock_irq(&rnp->lock);
+ cond_resched();
}
+ rnp = rcu_get_root(rsp);
+ raw_spin_lock_irq(&rnp->lock);
- rsp->completed = rsp->gpnum; /* Declare the grace period complete. */
+ rsp->completed = rsp->gpnum; /* Declare grace period done. */
trace_rcu_grace_period(rsp->name, rsp->completed, "end");
rsp->fqs_state = RCU_GP_IDLE;
- rcu_start_gp(rsp, flags); /* releases root node's rnp->lock. */
+ rdp = this_cpu_ptr(rsp->rda);
+ if (cpu_needs_another_gp(rsp, rdp))
+ rsp->gp_flags = 1;
+ raw_spin_unlock_irq(&rnp->lock);
+}
+
+/*
+ * Body of kthread that handles grace periods.
+ */
+static int __noreturn rcu_gp_kthread(void *arg)
+{
+ int fqs_state;
+ unsigned long j;
+ int ret;
+ struct rcu_state *rsp = arg;
+ struct rcu_node *rnp = rcu_get_root(rsp);
+
+ for (;;) {
+
+ /* Handle grace-period start. */
+ for (;;) {
+ wait_event_interruptible(rsp->gp_wq,
+ rsp->gp_flags &
+ RCU_GP_FLAG_INIT);
+ if ((rsp->gp_flags & RCU_GP_FLAG_INIT) &&
+ rcu_gp_init(rsp))
+ break;
+ cond_resched();
+ flush_signals(current);
+ }
+
+ /* Handle quiescent-state forcing. */
+ fqs_state = RCU_SAVE_DYNTICK;
+ j = jiffies_till_first_fqs;
+ if (j > HZ) {
+ j = HZ;
+ jiffies_till_first_fqs = HZ;
+ }
+ for (;;) {
+ rsp->jiffies_force_qs = jiffies + j;
+ ret = wait_event_interruptible_timeout(rsp->gp_wq,
+ (rsp->gp_flags & RCU_GP_FLAG_FQS) ||
+ (!ACCESS_ONCE(rnp->qsmask) &&
+ !rcu_preempt_blocked_readers_cgp(rnp)),
+ j);
+ /* If grace period done, leave loop. */
+ if (!ACCESS_ONCE(rnp->qsmask) &&
+ !rcu_preempt_blocked_readers_cgp(rnp))
+ break;
+ /* If time for quiescent-state forcing, do it. */
+ if (ret == 0 || (rsp->gp_flags & RCU_GP_FLAG_FQS)) {
+ fqs_state = rcu_gp_fqs(rsp, fqs_state);
+ cond_resched();
+ } else {
+ /* Deal with stray signal. */
+ cond_resched();
+ flush_signals(current);
+ }
+ j = jiffies_till_next_fqs;
+ if (j > HZ) {
+ j = HZ;
+ jiffies_till_next_fqs = HZ;
+ } else if (j < 1) {
+ j = 1;
+ jiffies_till_next_fqs = 1;
+ }
+ }
+
+ /* Handle grace-period end. */
+ rcu_gp_cleanup(rsp);
+ }
+}
+
+/*
+ * Start a new RCU grace period if warranted, re-initializing the hierarchy
+ * in preparation for detecting the next grace period. The caller must hold
+ * the root node's ->lock, which is released before return. Hard irqs must
+ * be disabled.
+ *
+ * Note that it is legal for a dying CPU (which is marked as offline) to
+ * invoke this function. This can happen when the dying CPU reports its
+ * quiescent state.
+ */
+static void
+rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
+ __releases(rcu_get_root(rsp)->lock)
+{
+ struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
+ struct rcu_node *rnp = rcu_get_root(rsp);
+
+ if (!rsp->gp_kthread ||
+ !cpu_needs_another_gp(rsp, rdp)) {
+ /*
+ * Either we have not yet spawned the grace-period
+ * task or this CPU does not need another grace period.
+ * Either way, don't start a new grace period.
+ */
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ return;
+ }
+
+ rsp->gp_flags = RCU_GP_FLAG_INIT;
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ wake_up(&rsp->gp_wq);
+}
+
+/*
+ * Report a full set of quiescent states to the specified rcu_state
+ * data structure. This involves cleaning up after the prior grace
+ * period and letting rcu_start_gp() start up the next grace period
+ * if one is needed. Note that the caller must hold rnp->lock, as
+ * required by rcu_start_gp(), which will release it.
+ */
+static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags)
+ __releases(rcu_get_root(rsp)->lock)
+{
+ WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
+ raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags);
+ wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */
}
/*
* based on quiescent states detected in an earlier grace period!
*/
static void
-rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastgp)
+rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
{
unsigned long flags;
unsigned long mask;
rnp = rdp->mynode;
raw_spin_lock_irqsave(&rnp->lock, flags);
- if (lastgp != rnp->gpnum || rnp->completed == rnp->gpnum) {
+ if (rdp->passed_quiesce == 0 || rdp->gpnum != rnp->gpnum ||
+ rnp->completed == rnp->gpnum) {
/*
* The grace period in which this quiescent state was
* Tell RCU we are done (but rcu_report_qs_rdp() will be the
* judge of that).
*/
- rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesce_gpnum);
+ rcu_report_qs_rdp(rdp->cpu, rsp, rdp);
}
#ifdef CONFIG_HOTPLUG_CPU
struct rcu_node *rnp;
rcu_for_each_leaf_node(rsp, rnp) {
+ cond_resched();
mask = 0;
raw_spin_lock_irqsave(&rnp->lock, flags);
if (!rcu_gp_in_progress(rsp)) {
* Force quiescent states on reluctant CPUs, and also detect which
* CPUs are in dyntick-idle mode.
*/
-static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
+static void force_quiescent_state(struct rcu_state *rsp)
{
unsigned long flags;
- struct rcu_node *rnp = rcu_get_root(rsp);
-
- trace_rcu_utilization("Start fqs");
- if (!rcu_gp_in_progress(rsp)) {
- trace_rcu_utilization("End fqs");
- return; /* No grace period in progress, nothing to force. */
- }
- if (!raw_spin_trylock_irqsave(&rsp->fqslock, flags)) {
- rsp->n_force_qs_lh++; /* Inexact, can lose counts. Tough! */
- trace_rcu_utilization("End fqs");
- return; /* Someone else is already on the job. */
- }
- if (relaxed && ULONG_CMP_GE(rsp->jiffies_force_qs, jiffies))
- goto unlock_fqs_ret; /* no emergency and done recently. */
- rsp->n_force_qs++;
- raw_spin_lock(&rnp->lock); /* irqs already disabled */
- rsp->jiffies_force_qs = jiffies + RCU_JIFFIES_TILL_FORCE_QS;
- if(!rcu_gp_in_progress(rsp)) {
- rsp->n_force_qs_ngp++;
- raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
- goto unlock_fqs_ret; /* no GP in progress, time updated. */
- }
- rsp->fqs_active = 1;
- switch (rsp->fqs_state) {
- case RCU_GP_IDLE:
- case RCU_GP_INIT:
-
- break; /* grace period idle or initializing, ignore. */
-
- case RCU_SAVE_DYNTICK:
-
- raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
-
- /* Record dyntick-idle state. */
- force_qs_rnp(rsp, dyntick_save_progress_counter);
- raw_spin_lock(&rnp->lock); /* irqs already disabled */
- if (rcu_gp_in_progress(rsp))
- rsp->fqs_state = RCU_FORCE_QS;
- break;
-
- case RCU_FORCE_QS:
-
- /* Check dyntick-idle state, send IPI to laggarts. */
- raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
- force_qs_rnp(rsp, rcu_implicit_dynticks_qs);
-
- /* Leave state in case more forcing is required. */
-
- raw_spin_lock(&rnp->lock); /* irqs already disabled */
- break;
+ bool ret;
+ struct rcu_node *rnp;
+ struct rcu_node *rnp_old = NULL;
+
+ /* Funnel through hierarchy to reduce memory contention. */
+ rnp = per_cpu_ptr(rsp->rda, raw_smp_processor_id())->mynode;
+ for (; rnp != NULL; rnp = rnp->parent) {
+ ret = (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) ||
+ !raw_spin_trylock(&rnp->fqslock);
+ if (rnp_old != NULL)
+ raw_spin_unlock(&rnp_old->fqslock);
+ if (ret) {
+ rsp->n_force_qs_lh++;
+ return;
+ }
+ rnp_old = rnp;
}
- rsp->fqs_active = 0;
- if (rsp->fqs_need_gp) {
- raw_spin_unlock(&rsp->fqslock); /* irqs remain disabled */
- rsp->fqs_need_gp = 0;
- rcu_start_gp(rsp, flags); /* releases rnp->lock */
- trace_rcu_utilization("End fqs");
- return;
+ /* rnp_old == rcu_get_root(rsp), rnp == NULL. */
+
+ /* Reached the root of the rcu_node tree, acquire lock. */
+ raw_spin_lock_irqsave(&rnp_old->lock, flags);
+ raw_spin_unlock(&rnp_old->fqslock);
+ if (ACCESS_ONCE(rsp->gp_flags) & RCU_GP_FLAG_FQS) {
+ rsp->n_force_qs_lh++;
+ raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
+ return; /* Someone beat us to it. */
}
- raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
-unlock_fqs_ret:
- raw_spin_unlock_irqrestore(&rsp->fqslock, flags);
- trace_rcu_utilization("End fqs");
+ rsp->gp_flags |= RCU_GP_FLAG_FQS;
+ raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
+ wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */
}
/*
WARN_ON_ONCE(rdp->beenonline == 0);
- /*
- * If an RCU GP has gone long enough, go check for dyntick
- * idle CPUs and, if needed, send resched IPIs.
- */
- if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
- force_quiescent_state(rsp, 1);
-
/*
* Advance callbacks in response to end of earlier grace
* period that some other CPU ended.
{
struct rcu_state *rsp;
+ if (cpu_is_offline(smp_processor_id()))
+ return;
trace_rcu_utilization("Start RCU core");
for_each_rcu_flavor(rsp)
__rcu_process_callbacks(rsp);
rdp->blimit = LONG_MAX;
if (rsp->n_force_qs == rdp->n_force_qs_snap &&
*rdp->nxttail[RCU_DONE_TAIL] != head)
- force_quiescent_state(rsp, 0);
+ force_quiescent_state(rsp);
rdp->n_force_qs_snap = rsp->n_force_qs;
rdp->qlen_last_fqs_check = rdp->qlen;
}
- } else if (ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies))
- force_quiescent_state(rsp, 1);
+ }
}
static void
/* Is the RCU core waiting for a quiescent state from this CPU? */
if (rcu_scheduler_fully_active &&
rdp->qs_pending && !rdp->passed_quiesce) {
-
- /*
- * If force_quiescent_state() coming soon and this CPU
- * needs a quiescent state, and this is either RCU-sched
- * or RCU-bh, force a local reschedule.
- */
rdp->n_rp_qs_pending++;
- if (!rdp->preemptible &&
- ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1,
- jiffies))
- set_need_resched();
} else if (rdp->qs_pending && rdp->passed_quiesce) {
rdp->n_rp_report_qs++;
return 1;
return 1;
}
- /* Has an RCU GP gone long enough to send resched IPIs &c? */
- if (rcu_gp_in_progress(rsp) &&
- ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs), jiffies)) {
- rdp->n_rp_need_fqs++;
- return 1;
- }
-
/* nothing to do */
rdp->n_rp_need_nothing++;
return 0;
rdp->completed = rnp->completed;
rdp->passed_quiesce = 0;
rdp->qs_pending = 0;
- rdp->passed_quiesce_gpnum = rnp->gpnum - 1;
trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuonl");
}
raw_spin_unlock(&rnp->lock); /* irqs already disabled. */
return NOTIFY_OK;
}
+/*
+ * Spawn the kthread that handles this RCU flavor's grace periods.
+ */
+static int __init rcu_spawn_gp_kthread(void)
+{
+ unsigned long flags;
+ struct rcu_node *rnp;
+ struct rcu_state *rsp;
+ struct task_struct *t;
+
+ for_each_rcu_flavor(rsp) {
+ t = kthread_run(rcu_gp_kthread, rsp, rsp->name);
+ BUG_ON(IS_ERR(t));
+ rnp = rcu_get_root(rsp);
+ raw_spin_lock_irqsave(&rnp->lock, flags);
+ rsp->gp_kthread = t;
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ }
+ return 0;
+}
+early_initcall(rcu_spawn_gp_kthread);
+
/*
* This function is invoked towards the end of the scheduler's initialization
* process. Before this is called, the idle task might contain
static void __init rcu_init_one(struct rcu_state *rsp,
struct rcu_data __percpu *rda)
{
- static char *buf[] = { "rcu_node_level_0",
- "rcu_node_level_1",
- "rcu_node_level_2",
- "rcu_node_level_3" }; /* Match MAX_RCU_LVLS */
+ static char *buf[] = { "rcu_node_0",
+ "rcu_node_1",
+ "rcu_node_2",
+ "rcu_node_3" }; /* Match MAX_RCU_LVLS */
+ static char *fqs[] = { "rcu_node_fqs_0",
+ "rcu_node_fqs_1",
+ "rcu_node_fqs_2",
+ "rcu_node_fqs_3" }; /* Match MAX_RCU_LVLS */
int cpustride = 1;
int i;
int j;
raw_spin_lock_init(&rnp->lock);
lockdep_set_class_and_name(&rnp->lock,
&rcu_node_class[i], buf[i]);
- rnp->gpnum = 0;
+ raw_spin_lock_init(&rnp->fqslock);
+ lockdep_set_class_and_name(&rnp->fqslock,
+ &rcu_fqs_class[i], fqs[i]);
+ rnp->gpnum = rsp->gpnum;
+ rnp->completed = rsp->completed;
rnp->qsmask = 0;
rnp->qsmaskinit = 0;
rnp->grplo = j * cpustride;
}
rsp->rda = rda;
+ init_waitqueue_head(&rsp->gp_wq);
rnp = rsp->level[rcu_num_lvls - 1];
for_each_possible_cpu(i) {
while (i > rnp->grphi)
projects / deliverable / linux.git / blobdiff