#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/nmi.h>
-#include <asm/atomic.h>
+#include <linux/atomic.h>
#include <linux/bitops.h>
-#include <linux/module.h>
+#include <linux/export.h>
#include <linux/completion.h>
#include <linux/moduleparam.h>
#include <linux/percpu.h>
#include <linux/kernel_stat.h>
#include <linux/wait.h>
#include <linux/kthread.h>
+#include <linux/prefetch.h>
+#include <linux/delay.h>
+#include <linux/stop_machine.h>
#include "rcutree.h"
+#include <trace/events/rcu.h>
+
+#include "rcu.h"
/* Data structures. */
static struct lock_class_key rcu_node_class[NUM_RCU_LVLS];
#define RCU_STATE_INITIALIZER(structname) { \
- .level = { &structname.node[0] }, \
+ .level = { &structname##_state.node[0] }, \
.levelcnt = { \
NUM_RCU_LVL_0, /* root of hierarchy. */ \
NUM_RCU_LVL_1, \
NUM_RCU_LVL_3, \
NUM_RCU_LVL_4, /* == MAX_RCU_LVLS */ \
}, \
- .signaled = RCU_GP_IDLE, \
+ .fqs_state = RCU_GP_IDLE, \
.gpnum = -300, \
.completed = -300, \
- .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname.onofflock), \
- .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&structname.fqslock), \
+ .onofflock = __RAW_SPIN_LOCK_UNLOCKED(&structname##_state.onofflock), \
+ .fqslock = __RAW_SPIN_LOCK_UNLOCKED(&structname##_state.fqslock), \
.n_force_qs = 0, \
.n_force_qs_ngp = 0, \
.name = #structname, \
}
-struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched_state);
+struct rcu_state rcu_sched_state = RCU_STATE_INITIALIZER(rcu_sched);
DEFINE_PER_CPU(struct rcu_data, rcu_sched_data);
-struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh_state);
+struct rcu_state rcu_bh_state = RCU_STATE_INITIALIZER(rcu_bh);
DEFINE_PER_CPU(struct rcu_data, rcu_bh_data);
static struct rcu_state *rcu_state;
+/*
+ * The rcu_scheduler_active variable transitions from zero to one just
+ * before the first task is spawned. So when this variable is zero, RCU
+ * can assume that there is but one task, allowing RCU to (for example)
+ * optimized synchronize_sched() to a simple barrier(). When this variable
+ * is one, RCU must actually do all the hard work required to detect real
+ * grace periods. This variable is also used to suppress boot-time false
+ * positives from lockdep-RCU error checking.
+ */
int rcu_scheduler_active __read_mostly;
EXPORT_SYMBOL_GPL(rcu_scheduler_active);
/*
+ * The rcu_scheduler_fully_active variable transitions from zero to one
+ * during the early_initcall() processing, which is after the scheduler
+ * is capable of creating new tasks. So RCU processing (for example,
+ * creating tasks for RCU priority boosting) must be delayed until after
+ * rcu_scheduler_fully_active transitions from zero to one. We also
+ * currently delay invocation of any RCU callbacks until after this point.
+ *
+ * It might later prove better for people registering RCU callbacks during
+ * early boot to take responsibility for these callbacks, but one step at
+ * a time.
+ */
+static int rcu_scheduler_fully_active __read_mostly;
+
+#ifdef CONFIG_RCU_BOOST
+
+/*
* Control variables for per-CPU and per-rcu_node kthreads. These
* handle all flavors of RCU.
*/
DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_status);
DEFINE_PER_CPU(int, rcu_cpu_kthread_cpu);
DEFINE_PER_CPU(unsigned int, rcu_cpu_kthread_loops);
-static DEFINE_PER_CPU(wait_queue_head_t, rcu_cpu_wq);
DEFINE_PER_CPU(char, rcu_cpu_has_work);
-static char rcu_kthreads_spawnable;
-static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
-static void invoke_rcu_cpu_kthread(void);
+#endif /* #ifdef CONFIG_RCU_BOOST */
-#define RCU_KTHREAD_PRIO 1 /* RT priority for per-CPU kthreads. */
+static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu);
+static void invoke_rcu_core(void);
+static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp);
/*
* Track the rcutorture test sequence number and the update version
* Note a quiescent state. Because we do not need to know
* how many quiescent states passed, just if there was at least
* one since the start of the grace period, this just sets a flag.
+ * The caller must have disabled preemption.
*/
void rcu_sched_qs(int cpu)
{
struct rcu_data *rdp = &per_cpu(rcu_sched_data, cpu);
- rdp->passed_quiesc_completed = rdp->gpnum - 1;
+ rdp->passed_quiesce_gpnum = rdp->gpnum;
barrier();
- rdp->passed_quiesc = 1;
+ if (rdp->passed_quiesce == 0)
+ trace_rcu_grace_period("rcu_sched", rdp->gpnum, "cpuqs");
+ rdp->passed_quiesce = 1;
}
void rcu_bh_qs(int cpu)
{
struct rcu_data *rdp = &per_cpu(rcu_bh_data, cpu);
- rdp->passed_quiesc_completed = rdp->gpnum - 1;
+ rdp->passed_quiesce_gpnum = rdp->gpnum;
barrier();
- rdp->passed_quiesc = 1;
+ if (rdp->passed_quiesce == 0)
+ trace_rcu_grace_period("rcu_bh", rdp->gpnum, "cpuqs");
+ rdp->passed_quiesce = 1;
}
/*
* Note a context switch. This is a quiescent state for RCU-sched,
* and requires special handling for preemptible RCU.
+ * The caller must have disabled preemption.
*/
void rcu_note_context_switch(int cpu)
{
+ trace_rcu_utilization("Start context switch");
rcu_sched_qs(cpu);
rcu_preempt_note_context_switch(cpu);
+ trace_rcu_utilization("End context switch");
}
+EXPORT_SYMBOL_GPL(rcu_note_context_switch);
-#ifdef CONFIG_NO_HZ
DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
- .dynticks_nesting = 1,
+ .dynticks_nesting = DYNTICK_TASK_EXIT_IDLE,
.dynticks = ATOMIC_INIT(1),
};
-#endif /* #ifdef CONFIG_NO_HZ */
-static int blimit = 10; /* Maximum callbacks per softirq. */
+static int blimit = 10; /* Maximum callbacks per rcu_do_batch. */
static int qhimark = 10000; /* If this many pending, ignore blimit. */
static int qlowmark = 100; /* Once only this many pending, use blimit. */
module_param(qhimark, int, 0);
module_param(qlowmark, int, 0);
-int rcu_cpu_stall_suppress __read_mostly;
+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 int rcu_pending(int cpu);
return &rsp->node[0];
}
-#ifdef CONFIG_SMP
-
/*
* If the specified CPU is offline, tell the caller that it is in
* a quiescent state. Otherwise, whack it with a reschedule IPI.
static int rcu_implicit_offline_qs(struct rcu_data *rdp)
{
/*
- * If the CPU is offline, it is in a quiescent state. We can
- * trust its state not to change because interrupts are disabled.
+ * If the CPU is offline for more than a jiffy, it is in a quiescent
+ * state. We can trust its state not to change because interrupts
+ * are disabled. The reason for the jiffy's worth of slack is to
+ * handle CPUs initializing on the way up and finding their way
+ * to the idle loop on the way down.
*/
- if (cpu_is_offline(rdp->cpu)) {
+ if (cpu_is_offline(rdp->cpu) &&
+ ULONG_CMP_LT(rdp->rsp->gp_start + 2, jiffies)) {
+ trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "ofl");
rdp->offline_fqs++;
return 1;
}
-
- /* If preemptible RCU, no point in sending reschedule IPI. */
- if (rdp->preemptible)
- return 0;
-
- /* The CPU is online, so send it a reschedule IPI. */
- if (rdp->cpu != smp_processor_id())
- smp_send_reschedule(rdp->cpu);
- else
- set_need_resched();
- rdp->resched_ipi++;
return 0;
}
-#endif /* #ifdef CONFIG_SMP */
+/*
+ * rcu_idle_enter_common - inform RCU that current CPU is moving towards idle
+ *
+ * If the new value of the ->dynticks_nesting counter now is zero,
+ * we really have entered idle, and must do the appropriate accounting.
+ * The caller must have disabled interrupts.
+ */
+static void rcu_idle_enter_common(struct rcu_dynticks *rdtp, long long oldval)
+{
+ trace_rcu_dyntick("Start", oldval, 0);
+ if (!is_idle_task(current)) {
+ struct task_struct *idle = idle_task(smp_processor_id());
-#ifdef CONFIG_NO_HZ
+ trace_rcu_dyntick("Error on entry: not idle task", oldval, 0);
+ ftrace_dump(DUMP_ALL);
+ WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
+ current->pid, current->comm,
+ idle->pid, idle->comm); /* must be idle task! */
+ }
+ rcu_prepare_for_idle(smp_processor_id());
+ /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
+ smp_mb__before_atomic_inc(); /* See above. */
+ atomic_inc(&rdtp->dynticks);
+ smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */
+ WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
+
+ /*
+ * The idle task is not permitted to enter the idle loop while
+ * in an RCU read-side critical section.
+ */
+ rcu_lockdep_assert(!lock_is_held(&rcu_lock_map),
+ "Illegal idle entry in RCU read-side critical section.");
+ rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map),
+ "Illegal idle entry in RCU-bh read-side critical section.");
+ rcu_lockdep_assert(!lock_is_held(&rcu_sched_lock_map),
+ "Illegal idle entry in RCU-sched read-side critical section.");
+}
/**
- * rcu_enter_nohz - inform RCU that current CPU is entering nohz
+ * rcu_idle_enter - inform RCU that current CPU is entering idle
*
- * Enter nohz mode, in other words, -leave- the mode in which RCU
+ * Enter idle mode, in other words, -leave- the mode in which RCU
* read-side critical sections can occur. (Though RCU read-side
- * critical sections can occur in irq handlers in nohz mode, a possibility
- * handled by rcu_irq_enter() and rcu_irq_exit()).
+ * critical sections can occur in irq handlers in idle, a possibility
+ * handled by irq_enter() and irq_exit().)
+ *
+ * We crowbar the ->dynticks_nesting field to zero to allow for
+ * the possibility of usermode upcalls having messed up our count
+ * of interrupt nesting level during the prior busy period.
*/
-void rcu_enter_nohz(void)
+void rcu_idle_enter(void)
{
unsigned long flags;
+ long long oldval;
struct rcu_dynticks *rdtp;
local_irq_save(flags);
rdtp = &__get_cpu_var(rcu_dynticks);
- if (--rdtp->dynticks_nesting) {
- local_irq_restore(flags);
- return;
- }
- /* CPUs seeing atomic_inc() must see prior RCU read-side crit sects */
- smp_mb__before_atomic_inc(); /* See above. */
- atomic_inc(&rdtp->dynticks);
- smp_mb__after_atomic_inc(); /* Force ordering with next sojourn. */
- WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
+ oldval = rdtp->dynticks_nesting;
+ WARN_ON_ONCE((oldval & DYNTICK_TASK_NEST_MASK) == 0);
+ if ((oldval & DYNTICK_TASK_NEST_MASK) == DYNTICK_TASK_NEST_VALUE)
+ rdtp->dynticks_nesting = 0;
+ else
+ rdtp->dynticks_nesting -= DYNTICK_TASK_NEST_VALUE;
+ rcu_idle_enter_common(rdtp, oldval);
local_irq_restore(flags);
-
- /* If the interrupt queued a callback, get out of dyntick mode. */
- if (in_irq() &&
- (__get_cpu_var(rcu_sched_data).nxtlist ||
- __get_cpu_var(rcu_bh_data).nxtlist ||
- rcu_preempt_needs_cpu(smp_processor_id())))
- set_need_resched();
}
+EXPORT_SYMBOL_GPL(rcu_idle_enter);
-/*
- * rcu_exit_nohz - inform RCU that current CPU is leaving nohz
+/**
+ * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle
+ *
+ * Exit from an interrupt handler, which might possibly result in entering
+ * idle mode, in other words, leaving the mode in which read-side critical
+ * sections can occur.
+ *
+ * This code assumes that the idle loop never does anything that might
+ * result in unbalanced calls to irq_enter() and irq_exit(). If your
+ * architecture violates this assumption, RCU will give you what you
+ * deserve, good and hard. But very infrequently and irreproducibly.
+ *
+ * Use things like work queues to work around this limitation.
*
- * Exit nohz mode, in other words, -enter- the mode in which RCU
- * read-side critical sections normally occur.
+ * You have been warned.
*/
-void rcu_exit_nohz(void)
+void rcu_irq_exit(void)
{
unsigned long flags;
+ long long oldval;
struct rcu_dynticks *rdtp;
local_irq_save(flags);
rdtp = &__get_cpu_var(rcu_dynticks);
- if (rdtp->dynticks_nesting++) {
- local_irq_restore(flags);
- return;
- }
+ oldval = rdtp->dynticks_nesting;
+ rdtp->dynticks_nesting--;
+ WARN_ON_ONCE(rdtp->dynticks_nesting < 0);
+ if (rdtp->dynticks_nesting)
+ trace_rcu_dyntick("--=", oldval, rdtp->dynticks_nesting);
+ else
+ rcu_idle_enter_common(rdtp, oldval);
+ local_irq_restore(flags);
+}
+
+/*
+ * rcu_idle_exit_common - inform RCU that current CPU is moving away from idle
+ *
+ * If the new value of the ->dynticks_nesting counter was previously zero,
+ * we really have exited idle, and must do the appropriate accounting.
+ * The caller must have disabled interrupts.
+ */
+static void rcu_idle_exit_common(struct rcu_dynticks *rdtp, long long oldval)
+{
smp_mb__before_atomic_inc(); /* Force ordering w/previous sojourn. */
atomic_inc(&rdtp->dynticks);
/* CPUs seeing atomic_inc() must see later RCU read-side crit sects */
smp_mb__after_atomic_inc(); /* See above. */
WARN_ON_ONCE(!(atomic_read(&rdtp->dynticks) & 0x1));
+ rcu_cleanup_after_idle(smp_processor_id());
+ trace_rcu_dyntick("End", oldval, rdtp->dynticks_nesting);
+ if (!is_idle_task(current)) {
+ struct task_struct *idle = idle_task(smp_processor_id());
+
+ trace_rcu_dyntick("Error on exit: not idle task",
+ oldval, rdtp->dynticks_nesting);
+ ftrace_dump(DUMP_ALL);
+ WARN_ONCE(1, "Current pid: %d comm: %s / Idle pid: %d comm: %s",
+ current->pid, current->comm,
+ idle->pid, idle->comm); /* must be idle task! */
+ }
+}
+
+/**
+ * rcu_idle_exit - inform RCU that current CPU is leaving idle
+ *
+ * Exit idle mode, in other words, -enter- the mode in which RCU
+ * read-side critical sections can occur.
+ *
+ * We crowbar the ->dynticks_nesting field to DYNTICK_TASK_NEST to
+ * allow for the possibility of usermode upcalls messing up our count
+ * of interrupt nesting level during the busy period that is just
+ * now starting.
+ */
+void rcu_idle_exit(void)
+{
+ unsigned long flags;
+ struct rcu_dynticks *rdtp;
+ long long oldval;
+
+ local_irq_save(flags);
+ rdtp = &__get_cpu_var(rcu_dynticks);
+ oldval = rdtp->dynticks_nesting;
+ WARN_ON_ONCE(oldval < 0);
+ if (oldval & DYNTICK_TASK_NEST_MASK)
+ rdtp->dynticks_nesting += DYNTICK_TASK_NEST_VALUE;
+ else
+ rdtp->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
+ rcu_idle_exit_common(rdtp, oldval);
+ local_irq_restore(flags);
+}
+EXPORT_SYMBOL_GPL(rcu_idle_exit);
+
+/**
+ * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle
+ *
+ * Enter an interrupt handler, which might possibly result in exiting
+ * idle mode, in other words, entering the mode in which read-side critical
+ * sections can occur.
+ *
+ * Note that the Linux kernel is fully capable of entering an interrupt
+ * handler that it never exits, for example when doing upcalls to
+ * user mode! This code assumes that the idle loop never does upcalls to
+ * user mode. If your architecture does do upcalls from the idle loop (or
+ * does anything else that results in unbalanced calls to the irq_enter()
+ * and irq_exit() functions), RCU will give you what you deserve, good
+ * and hard. But very infrequently and irreproducibly.
+ *
+ * Use things like work queues to work around this limitation.
+ *
+ * You have been warned.
+ */
+void rcu_irq_enter(void)
+{
+ unsigned long flags;
+ struct rcu_dynticks *rdtp;
+ long long oldval;
+
+ local_irq_save(flags);
+ rdtp = &__get_cpu_var(rcu_dynticks);
+ oldval = rdtp->dynticks_nesting;
+ rdtp->dynticks_nesting++;
+ WARN_ON_ONCE(rdtp->dynticks_nesting == 0);
+ if (oldval)
+ trace_rcu_dyntick("++=", oldval, rdtp->dynticks_nesting);
+ else
+ rcu_idle_exit_common(rdtp, oldval);
local_irq_restore(flags);
}
WARN_ON_ONCE(atomic_read(&rdtp->dynticks) & 0x1);
}
+#ifdef CONFIG_PROVE_RCU
+
/**
- * rcu_irq_enter - inform RCU of entry to hard irq context
+ * rcu_is_cpu_idle - see if RCU thinks that the current CPU is idle
*
- * If the CPU was idle with dynamic ticks active, this updates the
- * rdtp->dynticks to let the RCU handling know that the CPU is active.
+ * If the current CPU is in its idle loop and is neither in an interrupt
+ * or NMI handler, return true.
*/
-void rcu_irq_enter(void)
+int rcu_is_cpu_idle(void)
{
- rcu_exit_nohz();
+ int ret;
+
+ preempt_disable();
+ ret = (atomic_read(&__get_cpu_var(rcu_dynticks).dynticks) & 0x1) == 0;
+ preempt_enable();
+ return ret;
}
+EXPORT_SYMBOL(rcu_is_cpu_idle);
-/**
- * rcu_irq_exit - inform RCU of exit from hard irq context
+#ifdef CONFIG_HOTPLUG_CPU
+
+/*
+ * Is the current CPU online? Disable preemption to avoid false positives
+ * that could otherwise happen due to the current CPU number being sampled,
+ * this task being preempted, its old CPU being taken offline, resuming
+ * on some other CPU, then determining that its old CPU is now offline.
+ * It is OK to use RCU on an offline processor during initial boot, hence
+ * the check for rcu_scheduler_fully_active. Note also that it is OK
+ * for a CPU coming online to use RCU for one jiffy prior to marking itself
+ * online in the cpu_online_mask. Similarly, it is OK for a CPU going
+ * offline to continue to use RCU for one jiffy after marking itself
+ * offline in the cpu_online_mask. This leniency is necessary given the
+ * non-atomic nature of the online and offline processing, for example,
+ * the fact that a CPU enters the scheduler after completing the CPU_DYING
+ * notifiers.
+ *
+ * This is also why RCU internally marks CPUs online during the
+ * CPU_UP_PREPARE phase and offline during the CPU_DEAD phase.
*
- * If the CPU was idle with dynamic ticks active, update the rdp->dynticks
- * to put let the RCU handling be aware that the CPU is going back to idle
- * with no ticks.
+ * Disable checking if in an NMI handler because we cannot safely report
+ * errors from NMI handlers anyway.
*/
-void rcu_irq_exit(void)
+bool rcu_lockdep_current_cpu_online(void)
{
- rcu_enter_nohz();
+ struct rcu_data *rdp;
+ struct rcu_node *rnp;
+ bool ret;
+
+ if (in_nmi())
+ return 1;
+ preempt_disable();
+ rdp = &__get_cpu_var(rcu_sched_data);
+ rnp = rdp->mynode;
+ ret = (rdp->grpmask & rnp->qsmaskinit) ||
+ !rcu_scheduler_fully_active;
+ preempt_enable();
+ return ret;
}
+EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online);
+
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
-#ifdef CONFIG_SMP
+#endif /* #ifdef CONFIG_PROVE_RCU */
+
+/**
+ * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle
+ *
+ * If the current CPU is idle or running at a first-level (not nested)
+ * interrupt from idle, return true. The caller must have at least
+ * disabled preemption.
+ */
+int rcu_is_cpu_rrupt_from_idle(void)
+{
+ return __get_cpu_var(rcu_dynticks).dynticks_nesting <= 1;
+}
/*
* Snapshot the specified CPU's dynticks counter so that we can later
static int dyntick_save_progress_counter(struct rcu_data *rdp)
{
rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks);
- return 0;
+ return (rdp->dynticks_snap & 0x1) == 0;
}
/*
*/
static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
{
- unsigned long curr;
- unsigned long snap;
+ unsigned int curr;
+ unsigned int snap;
- curr = (unsigned long)atomic_add_return(0, &rdp->dynticks->dynticks);
- snap = (unsigned long)rdp->dynticks_snap;
+ curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks);
+ snap = (unsigned int)rdp->dynticks_snap;
/*
* If the CPU passed through or entered a dynticks idle phase with
* read-side critical section that started before the beginning
* of the current RCU grace period.
*/
- if ((curr & 0x1) == 0 || ULONG_CMP_GE(curr, snap + 2)) {
+ if ((curr & 0x1) == 0 || UINT_CMP_GE(curr, snap + 2)) {
+ trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, "dti");
rdp->dynticks_fqs++;
return 1;
}
return rcu_implicit_offline_qs(rdp);
}
-#endif /* #ifdef CONFIG_SMP */
-
-#else /* #ifdef CONFIG_NO_HZ */
-
-#ifdef CONFIG_SMP
-
-static int dyntick_save_progress_counter(struct rcu_data *rdp)
+static int jiffies_till_stall_check(void)
{
- return 0;
-}
+ int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout);
-static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
-{
- return rcu_implicit_offline_qs(rdp);
+ /*
+ * Limit check must be consistent with the Kconfig limits
+ * for CONFIG_RCU_CPU_STALL_TIMEOUT.
+ */
+ if (till_stall_check < 3) {
+ ACCESS_ONCE(rcu_cpu_stall_timeout) = 3;
+ till_stall_check = 3;
+ } else if (till_stall_check > 300) {
+ ACCESS_ONCE(rcu_cpu_stall_timeout) = 300;
+ till_stall_check = 300;
+ }
+ return till_stall_check * HZ + RCU_STALL_DELAY_DELTA;
}
-#endif /* #ifdef CONFIG_SMP */
-
-#endif /* #else #ifdef CONFIG_NO_HZ */
-
-int rcu_cpu_stall_suppress __read_mostly;
-
static void record_gp_stall_check_time(struct rcu_state *rsp)
{
rsp->gp_start = jiffies;
- rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_CHECK;
+ rsp->jiffies_stall = jiffies + jiffies_till_stall_check();
}
static void print_other_cpu_stall(struct rcu_state *rsp)
int cpu;
long delta;
unsigned long flags;
+ int ndetected;
struct rcu_node *rnp = rcu_get_root(rsp);
/* Only let one CPU complain about others per time interval. */
raw_spin_unlock_irqrestore(&rnp->lock, flags);
return;
}
- rsp->jiffies_stall = jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
-
- /*
- * Now rat on any tasks that got kicked up to the root rcu_node
- * due to CPU offlining.
- */
- rcu_print_task_stall(rnp);
+ rsp->jiffies_stall = jiffies + 3 * jiffies_till_stall_check() + 3;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
/*
* See Documentation/RCU/stallwarn.txt for info on how to debug
* RCU CPU stall warnings.
*/
- printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks: {",
+ printk(KERN_ERR "INFO: %s detected stalls on CPUs/tasks:",
rsp->name);
+ print_cpu_stall_info_begin();
rcu_for_each_leaf_node(rsp, rnp) {
raw_spin_lock_irqsave(&rnp->lock, flags);
- rcu_print_task_stall(rnp);
+ ndetected += rcu_print_task_stall(rnp);
raw_spin_unlock_irqrestore(&rnp->lock, flags);
if (rnp->qsmask == 0)
continue;
for (cpu = 0; cpu <= rnp->grphi - rnp->grplo; cpu++)
- if (rnp->qsmask & (1UL << cpu))
- printk(" %d", rnp->grplo + cpu);
+ if (rnp->qsmask & (1UL << cpu)) {
+ print_cpu_stall_info(rsp, rnp->grplo + cpu);
+ ndetected++;
+ }
}
- printk("} (detected by %d, t=%ld jiffies)\n",
+
+ /*
+ * Now rat on any tasks that got kicked up to the root rcu_node
+ * due to CPU offlining.
+ */
+ rnp = rcu_get_root(rsp);
+ raw_spin_lock_irqsave(&rnp->lock, flags);
+ ndetected = rcu_print_task_stall(rnp);
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+
+ print_cpu_stall_info_end();
+ printk(KERN_CONT "(detected by %d, t=%ld jiffies)\n",
smp_processor_id(), (long)(jiffies - rsp->gp_start));
- trigger_all_cpu_backtrace();
+ if (ndetected == 0)
+ printk(KERN_ERR "INFO: Stall ended before state dump start\n");
+ else if (!trigger_all_cpu_backtrace())
+ dump_stack();
/* If so configured, complain about tasks blocking the grace period. */
* See Documentation/RCU/stallwarn.txt for info on how to debug
* RCU CPU stall warnings.
*/
- printk(KERN_ERR "INFO: %s detected stall on CPU %d (t=%lu jiffies)\n",
- rsp->name, smp_processor_id(), jiffies - rsp->gp_start);
- trigger_all_cpu_backtrace();
+ printk(KERN_ERR "INFO: %s self-detected stall on CPU", rsp->name);
+ print_cpu_stall_info_begin();
+ print_cpu_stall_info(rsp, smp_processor_id());
+ print_cpu_stall_info_end();
+ printk(KERN_CONT " (t=%lu jiffies)\n", jiffies - rsp->gp_start);
+ if (!trigger_all_cpu_backtrace())
+ dump_stack();
raw_spin_lock_irqsave(&rnp->lock, flags);
if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall))
- rsp->jiffies_stall =
- jiffies + RCU_SECONDS_TILL_STALL_RECHECK;
+ rsp->jiffies_stall = jiffies +
+ 3 * jiffies_till_stall_check() + 3;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
set_need_resched(); /* kick ourselves to get things going. */
static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
{
- long delta;
+ unsigned long j;
+ unsigned long js;
struct rcu_node *rnp;
if (rcu_cpu_stall_suppress)
return;
- delta = jiffies - ACCESS_ONCE(rsp->jiffies_stall);
+ j = ACCESS_ONCE(jiffies);
+ js = ACCESS_ONCE(rsp->jiffies_stall);
rnp = rdp->mynode;
- if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && delta >= 0) {
+ if ((ACCESS_ONCE(rnp->qsmask) & rdp->grpmask) && ULONG_CMP_GE(j, js)) {
/* We haven't checked in, so go dump stack. */
print_cpu_stall(rsp);
- } else if (rcu_gp_in_progress(rsp) && delta >= RCU_STALL_RAT_DELAY) {
+ } else if (rcu_gp_in_progress(rsp) &&
+ ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY)) {
- /* They had two time units to dump stack, so complain. */
+ /* They had a few time units to dump stack, so complain. */
print_other_cpu_stall(rsp);
}
}
* go looking for one.
*/
rdp->gpnum = rnp->gpnum;
+ trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpustart");
if (rnp->qsmask & rdp->grpmask) {
rdp->qs_pending = 1;
- rdp->passed_quiesc = 0;
+ rdp->passed_quiesce = 0;
} else
rdp->qs_pending = 0;
+ zero_cpu_stall_ticks(rdp);
}
}
/* Remember that we saw this grace-period completion. */
rdp->completed = rnp->completed;
+ trace_rcu_grace_period(rsp->name, rdp->gpnum, "cpuend");
/*
* If we were in an extended quiescent state, we may have
* 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)
struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
struct rcu_node *rnp = rcu_get_root(rsp);
- if (!cpu_needs_another_gp(rsp, rdp) || rsp->fqs_active) {
- if (cpu_needs_another_gp(rsp, rdp))
- rsp->fqs_need_gp = 1;
- if (rnp->completed == rsp->completed) {
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- return;
- }
- raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
+ 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;
+ }
+ if (rsp->fqs_active) {
/*
- * 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 CPU needs a grace period, but force_quiescent_state()
+ * is running. Tell it to start one on this CPU's behalf.
*/
- rcu_for_each_node_breadth_first(rsp, rnp) {
- raw_spin_lock(&rnp->lock); /* irqs already disabled. */
- rnp->completed = rsp->completed;
- raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
- }
- local_irq_restore(flags);
+ rsp->fqs_need_gp = 1;
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
return;
}
/* Advance to a new grace period and initialize state. */
rsp->gpnum++;
- WARN_ON_ONCE(rsp->signaled == RCU_GP_INIT);
- rsp->signaled = RCU_GP_INIT; /* Hold off force_quiescent_state. */
+ 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);
-
- /* Special-case the common single-level case. */
- if (NUM_RCU_NODES == 1) {
- rcu_preempt_check_blocked_tasks(rnp);
- rnp->qsmask = rnp->qsmaskinit;
- rnp->gpnum = rsp->gpnum;
- rnp->completed = rsp->completed;
- rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state OK. */
- rcu_start_gp_per_cpu(rsp, rnp, rdp);
- rcu_preempt_boost_start_gp(rnp);
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- return;
- }
-
raw_spin_unlock(&rnp->lock); /* leave irqs disabled. */
-
/* Exclude any concurrent CPU-hotplug operations. */
raw_spin_lock(&rsp->onofflock); /* irqs already disabled. */
if (rnp == rdp->mynode)
rcu_start_gp_per_cpu(rsp, rnp, rdp);
rcu_preempt_boost_start_gp(rnp);
+ 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. */
}
rnp = rcu_get_root(rsp);
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
- rsp->signaled = RCU_SIGNAL_INIT; /* force_quiescent_state now OK. */
+ 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);
}
__releases(rcu_get_root(rsp)->lock)
{
unsigned long gp_duration;
+ 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));
gp_duration = jiffies - rsp->gp_start;
if (gp_duration > rsp->gp_max)
rsp->gp_max = gp_duration;
- rsp->completed = rsp->gpnum;
- rsp->signaled = RCU_GP_IDLE;
+
+ /*
+ * We know the grace period is complete, but to everyone else
+ * it appears to still be ongoing. But it is also the case
+ * that to everyone else it looks like there is nothing that
+ * 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. */
+
+ /*
+ * 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. */
+ }
+
+ rsp->completed = rsp->gpnum; /* Declare the grace period complete. */
+ 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. */
}
return;
}
rnp->qsmask &= ~mask;
+ trace_rcu_quiescent_state_report(rsp->name, rnp->gpnum,
+ mask, rnp->qsmask, rnp->level,
+ rnp->grplo, rnp->grphi,
+ !!rnp->gp_tasks);
if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) {
/* Other bits still set at this level, so done. */
* 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 lastcomp)
+rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp, long lastgp)
{
unsigned long flags;
unsigned long mask;
rnp = rdp->mynode;
raw_spin_lock_irqsave(&rnp->lock, flags);
- if (lastcomp != rnp->completed) {
+ if (lastgp != rnp->gpnum || rnp->completed == rnp->gpnum) {
/*
- * Someone beat us to it for this grace period, so leave.
- * The race with GP start is resolved by the fact that we
- * hold the leaf rcu_node lock, so that the per-CPU bits
- * cannot yet be initialized -- so we would simply find our
- * CPU's bit already cleared in rcu_report_qs_rnp() if this
- * race occurred.
+ * The grace period in which this quiescent state was
+ * recorded has ended, so don't report it upwards.
+ * We will instead need a new quiescent state that lies
+ * within the current grace period.
*/
- rdp->passed_quiesc = 0; /* try again later! */
+ rdp->passed_quiesce = 0; /* need qs for new gp. */
raw_spin_unlock_irqrestore(&rnp->lock, flags);
return;
}
* Was there a quiescent state since the beginning of the grace
* period? If no, then exit and wait for the next call.
*/
- if (!rdp->passed_quiesc)
+ if (!rdp->passed_quiesce)
return;
/*
* 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_quiesc_completed);
+ rcu_report_qs_rdp(rdp->cpu, rsp, rdp, rdp->passed_quiesce_gpnum);
}
#ifdef CONFIG_HOTPLUG_CPU
/*
* Move a dying CPU's RCU callbacks to online CPU's callback list.
- * Synchronization is not required because this function executes
- * in stop_machine() context.
+ * Also record a quiescent state for this CPU for the current grace period.
+ * Synchronization and interrupt disabling are not required because
+ * this function executes in stop_machine() context. Therefore, cleanup
+ * operations that might block must be done later from the CPU_DEAD
+ * notifier.
+ *
+ * Note that the outgoing CPU's bit has already been cleared in the
+ * cpu_online_mask. This allows us to randomly pick a callback
+ * destination from the bits set in that mask.
*/
-static void rcu_send_cbs_to_online(struct rcu_state *rsp)
+static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
{
int i;
- /* current DYING CPU is cleared in the cpu_online_mask */
+ unsigned long mask;
int receive_cpu = cpumask_any(cpu_online_mask);
struct rcu_data *rdp = this_cpu_ptr(rsp->rda);
struct rcu_data *receive_rdp = per_cpu_ptr(rsp->rda, receive_cpu);
+ RCU_TRACE(struct rcu_node *rnp = rdp->mynode); /* For dying CPU. */
+
+ /* First, adjust the counts. */
+ if (rdp->nxtlist != NULL) {
+ receive_rdp->qlen_lazy += rdp->qlen_lazy;
+ receive_rdp->qlen += rdp->qlen;
+ rdp->qlen_lazy = 0;
+ rdp->qlen = 0;
+ }
- if (rdp->nxtlist == NULL)
- return; /* irqs disabled, so comparison is stable. */
+ /*
+ * Next, move ready-to-invoke callbacks to be invoked on some
+ * other CPU. These will not be required to pass through another
+ * grace period: They are done, regardless of CPU.
+ */
+ if (rdp->nxtlist != NULL &&
+ rdp->nxttail[RCU_DONE_TAIL] != &rdp->nxtlist) {
+ struct rcu_head *oldhead;
+ struct rcu_head **oldtail;
+ struct rcu_head **newtail;
+
+ oldhead = rdp->nxtlist;
+ oldtail = receive_rdp->nxttail[RCU_DONE_TAIL];
+ rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];
+ *rdp->nxttail[RCU_DONE_TAIL] = *oldtail;
+ *receive_rdp->nxttail[RCU_DONE_TAIL] = oldhead;
+ newtail = rdp->nxttail[RCU_DONE_TAIL];
+ for (i = RCU_DONE_TAIL; i < RCU_NEXT_SIZE; i++) {
+ if (receive_rdp->nxttail[i] == oldtail)
+ receive_rdp->nxttail[i] = newtail;
+ if (rdp->nxttail[i] == newtail)
+ rdp->nxttail[i] = &rdp->nxtlist;
+ }
+ }
- *receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist;
- receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
- receive_rdp->qlen += rdp->qlen;
- receive_rdp->n_cbs_adopted += rdp->qlen;
- rdp->n_cbs_orphaned += rdp->qlen;
+ /*
+ * Finally, put the rest of the callbacks at the end of the list.
+ * The ones that made it partway through get to start over: We
+ * cannot assume that grace periods are synchronized across CPUs.
+ * (We could splice RCU_WAIT_TAIL into RCU_NEXT_READY_TAIL, but
+ * this does not seem compelling. Not yet, anyway.)
+ */
+ if (rdp->nxtlist != NULL) {
+ *receive_rdp->nxttail[RCU_NEXT_TAIL] = rdp->nxtlist;
+ receive_rdp->nxttail[RCU_NEXT_TAIL] =
+ rdp->nxttail[RCU_NEXT_TAIL];
+ receive_rdp->n_cbs_adopted += rdp->qlen;
+ rdp->n_cbs_orphaned += rdp->qlen;
+
+ rdp->nxtlist = NULL;
+ for (i = 0; i < RCU_NEXT_SIZE; i++)
+ rdp->nxttail[i] = &rdp->nxtlist;
+ }
- rdp->nxtlist = NULL;
- for (i = 0; i < RCU_NEXT_SIZE; i++)
- rdp->nxttail[i] = &rdp->nxtlist;
- rdp->qlen = 0;
+ /*
+ * Record a quiescent state for the dying CPU. This is safe
+ * only because we have already cleared out the callbacks.
+ * (Otherwise, the RCU core might try to schedule the invocation
+ * of callbacks on this now-offline CPU, which would be bad.)
+ */
+ mask = rdp->grpmask; /* rnp->grplo is constant. */
+ trace_rcu_grace_period(rsp->name,
+ rnp->gpnum + 1 - !!(rnp->qsmask & mask),
+ "cpuofl");
+ rcu_report_qs_rdp(smp_processor_id(), rsp, rdp, rsp->gpnum);
+ /* Note that rcu_report_qs_rdp() might call trace_rcu_grace_period(). */
}
/*
- * Remove the outgoing CPU from the bitmasks in the rcu_node hierarchy
- * and move all callbacks from the outgoing CPU to the current one.
+ * The CPU has been completely removed, and some other CPU is reporting
+ * this fact from process context. Do the remainder of the cleanup.
* There can only be one CPU hotplug operation at a time, so no other
* CPU can be attempting to update rcu_cpu_kthread_task.
*/
-static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
+static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
{
unsigned long flags;
unsigned long mask;
int need_report = 0;
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
- struct rcu_node *rnp;
- struct task_struct *t;
+ struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rnp. */
- /* Stop the CPU's kthread. */
- t = per_cpu(rcu_cpu_kthread_task, cpu);
- if (t != NULL) {
- per_cpu(rcu_cpu_kthread_task, cpu) = NULL;
- kthread_stop(t);
- }
+ /* Adjust any no-longer-needed kthreads. */
+ rcu_stop_cpu_kthread(cpu);
+ rcu_node_kthread_setaffinity(rnp, -1);
+
+ /* Remove the dying CPU from the bitmasks in the rcu_node hierarchy. */
/* Exclude any attempts to start a new grace period. */
raw_spin_lock_irqsave(&rsp->onofflock, flags);
/* Remove the outgoing CPU from the masks in the rcu_node hierarchy. */
- rnp = rdp->mynode; /* this is the outgoing CPU's rnp. */
mask = rdp->grpmask; /* rnp->grplo is constant. */
do {
raw_spin_lock(&rnp->lock); /* irqs already disabled. */
else
raw_spin_unlock_irqrestore(&rnp->lock, flags);
if (need_report & RCU_OFL_TASKS_EXP_GP)
- rcu_report_exp_rnp(rsp, rnp);
-
- /*
- * If there are no more online CPUs for this rcu_node structure,
- * kill the rcu_node structure's kthread. Otherwise, adjust its
- * affinity.
- */
- t = rnp->node_kthread_task;
- if (t != NULL &&
- rnp->qsmaskinit == 0) {
- raw_spin_lock_irqsave(&rnp->lock, flags);
- rnp->node_kthread_task = NULL;
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- kthread_stop(t);
- rcu_stop_boost_kthread(rnp);
- } else
- rcu_node_kthread_setaffinity(rnp, -1);
-}
-
-/*
- * Remove the specified CPU from the RCU hierarchy and move any pending
- * callbacks that it might have to the current CPU. This code assumes
- * that at least one CPU in the system will remain running at all times.
- * Any attempt to offline -all- CPUs is likely to strand RCU callbacks.
- */
-static void rcu_offline_cpu(int cpu)
-{
- __rcu_offline_cpu(cpu, &rcu_sched_state);
- __rcu_offline_cpu(cpu, &rcu_bh_state);
- rcu_preempt_offline_cpu(cpu);
+ rcu_report_exp_rnp(rsp, rnp, true);
}
#else /* #ifdef CONFIG_HOTPLUG_CPU */
-static void rcu_send_cbs_to_online(struct rcu_state *rsp)
+static void rcu_cleanup_dying_cpu(struct rcu_state *rsp)
{
}
-static void rcu_offline_cpu(int cpu)
+static void rcu_cleanup_dead_cpu(int cpu, struct rcu_state *rsp)
{
}
{
unsigned long flags;
struct rcu_head *next, *list, **tail;
- int count;
+ int bl, count, count_lazy;
/* If no callbacks are ready, just return.*/
- if (!cpu_has_callbacks_ready_to_invoke(rdp))
+ if (!cpu_has_callbacks_ready_to_invoke(rdp)) {
+ trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, 0);
+ trace_rcu_batch_end(rsp->name, 0, !!ACCESS_ONCE(rdp->nxtlist),
+ need_resched(), is_idle_task(current),
+ rcu_is_callbacks_kthread());
return;
+ }
/*
* Extract the list of ready callbacks, disabling to prevent
* races with call_rcu() from interrupt handlers.
*/
local_irq_save(flags);
+ WARN_ON_ONCE(cpu_is_offline(smp_processor_id()));
+ bl = rdp->blimit;
+ trace_rcu_batch_start(rsp->name, rdp->qlen_lazy, rdp->qlen, bl);
list = rdp->nxtlist;
rdp->nxtlist = *rdp->nxttail[RCU_DONE_TAIL];
*rdp->nxttail[RCU_DONE_TAIL] = NULL;
local_irq_restore(flags);
/* Invoke callbacks. */
- count = 0;
+ count = count_lazy = 0;
while (list) {
next = list->next;
prefetch(next);
debug_rcu_head_unqueue(list);
- list->func(list);
+ if (__rcu_reclaim(rsp->name, list))
+ count_lazy++;
list = next;
- if (++count >= rdp->blimit)
+ /* Stop only if limit reached and CPU has something to do. */
+ if (++count >= bl &&
+ (need_resched() ||
+ (!is_idle_task(current) && !rcu_is_callbacks_kthread())))
break;
}
local_irq_save(flags);
+ trace_rcu_batch_end(rsp->name, count, !!list, need_resched(),
+ is_idle_task(current),
+ rcu_is_callbacks_kthread());
/* Update count, and requeue any remaining callbacks. */
+ rdp->qlen_lazy -= count_lazy;
rdp->qlen -= count;
rdp->n_cbs_invoked += count;
if (list != NULL) {
local_irq_restore(flags);
- /* Re-raise the RCU softirq if there are callbacks remaining. */
+ /* Re-invoke RCU core processing if there are callbacks remaining. */
if (cpu_has_callbacks_ready_to_invoke(rdp))
- invoke_rcu_cpu_kthread();
+ invoke_rcu_core();
}
/*
* Check to see if this CPU is in a non-context-switch quiescent state
* (user mode or idle loop for rcu, non-softirq execution for rcu_bh).
- * Also schedule the RCU softirq handler.
+ * Also schedule RCU core processing.
*
- * This function must be called with hardirqs disabled. It is normally
+ * This function must be called from hardirq context. It is normally
* invoked from the scheduling-clock interrupt. If rcu_pending returns
* false, there is no point in invoking rcu_check_callbacks().
*/
void rcu_check_callbacks(int cpu, int user)
{
- if (user ||
- (idle_cpu(cpu) && rcu_scheduler_active &&
- !in_softirq() && hardirq_count() <= (1 << HARDIRQ_SHIFT))) {
+ trace_rcu_utilization("Start scheduler-tick");
+ increment_cpu_stall_ticks();
+ if (user || rcu_is_cpu_rrupt_from_idle()) {
/*
* Get here if this CPU took its interrupt from user
}
rcu_preempt_check_callbacks(cpu);
if (rcu_pending(cpu))
- invoke_rcu_cpu_kthread();
+ invoke_rcu_core();
+ trace_rcu_utilization("End scheduler-tick");
}
-#ifdef CONFIG_SMP
-
/*
* Scan the leaf rcu_node structures, processing dyntick state for any that
* have not yet encountered a quiescent state, using the function specified.
return;
}
if (rnp->qsmask == 0) {
- rcu_initiate_boost(rnp);
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ rcu_initiate_boost(rnp, flags); /* releases rnp->lock */
continue;
}
cpu = rnp->grplo;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
rnp = rcu_get_root(rsp);
- raw_spin_lock_irqsave(&rnp->lock, flags);
- if (rnp->qsmask == 0)
- rcu_initiate_boost(rnp);
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ if (rnp->qsmask == 0) {
+ raw_spin_lock_irqsave(&rnp->lock, flags);
+ rcu_initiate_boost(rnp, flags); /* releases rnp->lock. */
+ }
}
/*
unsigned long flags;
struct rcu_node *rnp = rcu_get_root(rsp);
- if (!rcu_gp_in_progress(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 GP in progress, time updated. */
}
rsp->fqs_active = 1;
- switch (rsp->signaled) {
+ switch (rsp->fqs_state) {
case RCU_GP_IDLE:
case RCU_GP_INIT:
force_qs_rnp(rsp, dyntick_save_progress_counter);
raw_spin_lock(&rnp->lock); /* irqs already disabled */
if (rcu_gp_in_progress(rsp))
- rsp->signaled = RCU_FORCE_QS;
+ rsp->fqs_state = RCU_FORCE_QS;
break;
case RCU_FORCE_QS:
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;
}
raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
unlock_fqs_ret:
raw_spin_unlock_irqrestore(&rsp->fqslock, flags);
+ trace_rcu_utilization("End fqs");
}
-#else /* #ifdef CONFIG_SMP */
-
-static void force_quiescent_state(struct rcu_state *rsp, int relaxed)
-{
- set_need_resched();
-}
-
-#endif /* #else #ifdef CONFIG_SMP */
-
/*
- * This does the RCU processing work from softirq context for the
- * specified rcu_state and rcu_data structures. This may be called
- * only from the CPU to whom the rdp belongs.
+ * This does the RCU core processing work for the specified rcu_state
+ * and rcu_data structures. This may be called only from the CPU to
+ * whom the rdp belongs.
*/
static void
__rcu_process_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
}
/* If there are callbacks ready, invoke them. */
- rcu_do_batch(rsp, rdp);
+ if (cpu_has_callbacks_ready_to_invoke(rdp))
+ invoke_rcu_callbacks(rsp, rdp);
}
/*
- * Do softirq processing for the current CPU.
+ * Do RCU core processing for the current CPU.
*/
-static void rcu_process_callbacks(void)
+static void rcu_process_callbacks(struct softirq_action *unused)
{
+ trace_rcu_utilization("Start RCU core");
__rcu_process_callbacks(&rcu_sched_state,
&__get_cpu_var(rcu_sched_data));
__rcu_process_callbacks(&rcu_bh_state, &__get_cpu_var(rcu_bh_data));
rcu_preempt_process_callbacks();
-
- /* If we are last CPU on way to dyntick-idle mode, accelerate it. */
- rcu_needs_cpu_flush();
-}
-
-/*
- * Wake up the current CPU's kthread. This replaces raise_softirq()
- * in earlier versions of RCU. Note that because we are running on
- * the current CPU with interrupts disabled, the rcu_cpu_kthread_task
- * cannot disappear out from under us.
- */
-static void invoke_rcu_cpu_kthread(void)
-{
- unsigned long flags;
-
- local_irq_save(flags);
- __this_cpu_write(rcu_cpu_has_work, 1);
- if (__this_cpu_read(rcu_cpu_kthread_task) == NULL) {
- local_irq_restore(flags);
- return;
- }
- wake_up(&__get_cpu_var(rcu_cpu_wq));
- local_irq_restore(flags);
-}
-
-/*
- * Wake up the specified per-rcu_node-structure kthread.
- * The caller must hold ->lock.
- */
-static void invoke_rcu_node_kthread(struct rcu_node *rnp)
-{
- struct task_struct *t;
-
- t = rnp->node_kthread_task;
- if (t != NULL)
- wake_up_process(t);
-}
-
-/*
- * Set the specified CPU's kthread to run RT or not, as specified by
- * the to_rt argument. The CPU-hotplug locks are held, so the task
- * is not going away.
- */
-static void rcu_cpu_kthread_setrt(int cpu, int to_rt)
-{
- int policy;
- struct sched_param sp;
- struct task_struct *t;
-
- t = per_cpu(rcu_cpu_kthread_task, cpu);
- if (t == NULL)
- return;
- if (to_rt) {
- policy = SCHED_FIFO;
- sp.sched_priority = RCU_KTHREAD_PRIO;
- } else {
- policy = SCHED_NORMAL;
- sp.sched_priority = 0;
- }
- sched_setscheduler_nocheck(t, policy, &sp);
-}
-
-/*
- * Timer handler to initiate the waking up of per-CPU kthreads that
- * have yielded the CPU due to excess numbers of RCU callbacks.
- * We wake up the per-rcu_node kthread, which in turn will wake up
- * the booster kthread.
- */
-static void rcu_cpu_kthread_timer(unsigned long arg)
-{
- unsigned long flags;
- struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, arg);
- struct rcu_node *rnp = rdp->mynode;
-
- raw_spin_lock_irqsave(&rnp->lock, flags);
- rnp->wakemask |= rdp->grpmask;
- invoke_rcu_node_kthread(rnp);
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
-}
-
-/*
- * Drop to non-real-time priority and yield, but only after posting a
- * timer that will cause us to regain our real-time priority if we
- * remain preempted. Either way, we restore our real-time priority
- * before returning.
- */
-static void rcu_yield(void (*f)(unsigned long), unsigned long arg)
-{
- struct sched_param sp;
- struct timer_list yield_timer;
-
- setup_timer_on_stack(&yield_timer, f, arg);
- mod_timer(&yield_timer, jiffies + 2);
- sp.sched_priority = 0;
- sched_setscheduler_nocheck(current, SCHED_NORMAL, &sp);
- schedule();
- sp.sched_priority = RCU_KTHREAD_PRIO;
- sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
- del_timer(&yield_timer);
-}
-
-/*
- * Handle cases where the rcu_cpu_kthread() ends up on the wrong CPU.
- * This can happen while the corresponding CPU is either coming online
- * or going offline. We cannot wait until the CPU is fully online
- * before starting the kthread, because the various notifier functions
- * can wait for RCU grace periods. So we park rcu_cpu_kthread() until
- * the corresponding CPU is online.
- *
- * Return 1 if the kthread needs to stop, 0 otherwise.
- *
- * Caller must disable bh. This function can momentarily enable it.
- */
-static int rcu_cpu_kthread_should_stop(int cpu)
-{
- while (cpu_is_offline(cpu) ||
- !cpumask_equal(¤t->cpus_allowed, cpumask_of(cpu)) ||
- smp_processor_id() != cpu) {
- if (kthread_should_stop())
- return 1;
- per_cpu(rcu_cpu_kthread_status, cpu) = RCU_KTHREAD_OFFCPU;
- per_cpu(rcu_cpu_kthread_cpu, cpu) = raw_smp_processor_id();
- local_bh_enable();
- schedule_timeout_uninterruptible(1);
- if (!cpumask_equal(¤t->cpus_allowed, cpumask_of(cpu)))
- set_cpus_allowed_ptr(current, cpumask_of(cpu));
- local_bh_disable();
- }
- per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu;
- return 0;
-}
-
-/*
- * Per-CPU kernel thread that invokes RCU callbacks. This replaces the
- * earlier RCU softirq.
- */
-static int rcu_cpu_kthread(void *arg)
-{
- int cpu = (int)(long)arg;
- unsigned long flags;
- int spincnt = 0;
- unsigned int *statusp = &per_cpu(rcu_cpu_kthread_status, cpu);
- wait_queue_head_t *wqp = &per_cpu(rcu_cpu_wq, cpu);
- char work;
- char *workp = &per_cpu(rcu_cpu_has_work, cpu);
-
- for (;;) {
- *statusp = RCU_KTHREAD_WAITING;
- wait_event_interruptible(*wqp,
- *workp != 0 || kthread_should_stop());
- local_bh_disable();
- if (rcu_cpu_kthread_should_stop(cpu)) {
- local_bh_enable();
- break;
- }
- *statusp = RCU_KTHREAD_RUNNING;
- per_cpu(rcu_cpu_kthread_loops, cpu)++;
- local_irq_save(flags);
- work = *workp;
- *workp = 0;
- local_irq_restore(flags);
- if (work)
- rcu_process_callbacks();
- local_bh_enable();
- if (*workp != 0)
- spincnt++;
- else
- spincnt = 0;
- if (spincnt > 10) {
- *statusp = RCU_KTHREAD_YIELDING;
- rcu_yield(rcu_cpu_kthread_timer, (unsigned long)cpu);
- spincnt = 0;
- }
- }
- *statusp = RCU_KTHREAD_STOPPED;
- return 0;
-}
-
-/*
- * Spawn a per-CPU kthread, setting up affinity and priority.
- * Because the CPU hotplug lock is held, no other CPU will be attempting
- * to manipulate rcu_cpu_kthread_task. There might be another CPU
- * attempting to access it during boot, but the locking in kthread_bind()
- * will enforce sufficient ordering.
- */
-static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu)
-{
- struct sched_param sp;
- struct task_struct *t;
-
- if (!rcu_kthreads_spawnable ||
- per_cpu(rcu_cpu_kthread_task, cpu) != NULL)
- return 0;
- t = kthread_create(rcu_cpu_kthread, (void *)(long)cpu, "rcuc%d", cpu);
- if (IS_ERR(t))
- return PTR_ERR(t);
- kthread_bind(t, cpu);
- per_cpu(rcu_cpu_kthread_cpu, cpu) = cpu;
- WARN_ON_ONCE(per_cpu(rcu_cpu_kthread_task, cpu) != NULL);
- per_cpu(rcu_cpu_kthread_task, cpu) = t;
- wake_up_process(t);
- sp.sched_priority = RCU_KTHREAD_PRIO;
- sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
- return 0;
+ trace_rcu_utilization("End RCU core");
}
/*
- * Per-rcu_node kthread, which is in charge of waking up the per-CPU
- * kthreads when needed. We ignore requests to wake up kthreads
- * for offline CPUs, which is OK because force_quiescent_state()
- * takes care of this case.
- */
-static int rcu_node_kthread(void *arg)
-{
- int cpu;
- unsigned long flags;
- unsigned long mask;
- struct rcu_node *rnp = (struct rcu_node *)arg;
- struct sched_param sp;
- struct task_struct *t;
-
- for (;;) {
- rnp->node_kthread_status = RCU_KTHREAD_WAITING;
- wait_event_interruptible(rnp->node_wq, rnp->wakemask != 0 ||
- kthread_should_stop());
- if (kthread_should_stop())
- break;
- rnp->node_kthread_status = RCU_KTHREAD_RUNNING;
- raw_spin_lock_irqsave(&rnp->lock, flags);
- mask = rnp->wakemask;
- rnp->wakemask = 0;
- rcu_initiate_boost(rnp);
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1) {
- if ((mask & 0x1) == 0)
- continue;
- preempt_disable();
- t = per_cpu(rcu_cpu_kthread_task, cpu);
- if (!cpu_online(cpu) || t == NULL) {
- preempt_enable();
- continue;
- }
- per_cpu(rcu_cpu_has_work, cpu) = 1;
- sp.sched_priority = RCU_KTHREAD_PRIO;
- sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
- preempt_enable();
- }
- }
- rnp->node_kthread_status = RCU_KTHREAD_STOPPED;
- return 0;
-}
-
-/*
- * Set the per-rcu_node kthread's affinity to cover all CPUs that are
- * served by the rcu_node in question. The CPU hotplug lock is still
- * held, so the value of rnp->qsmaskinit will be stable.
- *
- * We don't include outgoingcpu in the affinity set, use -1 if there is
- * no outgoing CPU. If there are no CPUs left in the affinity set,
- * this function allows the kthread to execute on any CPU.
+ * Schedule RCU callback invocation. If the specified type of RCU
+ * does not support RCU priority boosting, just do a direct call,
+ * otherwise wake up the per-CPU kernel kthread. Note that because we
+ * are running on the current CPU with interrupts disabled, the
+ * rcu_cpu_kthread_task cannot disappear out from under us.
*/
-static void rcu_node_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu)
+static void invoke_rcu_callbacks(struct rcu_state *rsp, struct rcu_data *rdp)
{
- cpumask_var_t cm;
- int cpu;
- unsigned long mask = rnp->qsmaskinit;
-
- if (rnp->node_kthread_task == NULL || mask == 0)
+ if (unlikely(!ACCESS_ONCE(rcu_scheduler_fully_active)))
return;
- if (!alloc_cpumask_var(&cm, GFP_KERNEL))
+ if (likely(!rsp->boost)) {
+ rcu_do_batch(rsp, rdp);
return;
- cpumask_clear(cm);
- for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask >>= 1)
- if ((mask & 0x1) && cpu != outgoingcpu)
- cpumask_set_cpu(cpu, cm);
- if (cpumask_weight(cm) == 0) {
- cpumask_setall(cm);
- for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++)
- cpumask_clear_cpu(cpu, cm);
- WARN_ON_ONCE(cpumask_weight(cm) == 0);
}
- set_cpus_allowed_ptr(rnp->node_kthread_task, cm);
- rcu_boost_kthread_setaffinity(rnp, cm);
- free_cpumask_var(cm);
+ invoke_rcu_callbacks_kthread();
}
-/*
- * Spawn a per-rcu_node kthread, setting priority and affinity.
- * Called during boot before online/offline can happen, or, if
- * during runtime, with the main CPU-hotplug locks held. So only
- * one of these can be executing at a time.
- */
-static int __cpuinit rcu_spawn_one_node_kthread(struct rcu_state *rsp,
- struct rcu_node *rnp)
+static void invoke_rcu_core(void)
{
- unsigned long flags;
- int rnp_index = rnp - &rsp->node[0];
- struct sched_param sp;
- struct task_struct *t;
-
- if (!rcu_kthreads_spawnable ||
- rnp->qsmaskinit == 0)
- return 0;
- if (rnp->node_kthread_task == NULL) {
- t = kthread_create(rcu_node_kthread, (void *)rnp,
- "rcun%d", rnp_index);
- if (IS_ERR(t))
- return PTR_ERR(t);
- raw_spin_lock_irqsave(&rnp->lock, flags);
- rnp->node_kthread_task = t;
- raw_spin_unlock_irqrestore(&rnp->lock, flags);
- wake_up_process(t);
- sp.sched_priority = 99;
- sched_setscheduler_nocheck(t, SCHED_FIFO, &sp);
- }
- return rcu_spawn_one_boost_kthread(rsp, rnp, rnp_index);
+ raise_softirq(RCU_SOFTIRQ);
}
-/*
- * Spawn all kthreads -- called as soon as the scheduler is running.
- */
-static int __init rcu_spawn_kthreads(void)
-{
- int cpu;
- struct rcu_node *rnp;
-
- rcu_kthreads_spawnable = 1;
- for_each_possible_cpu(cpu) {
- init_waitqueue_head(&per_cpu(rcu_cpu_wq, cpu));
- per_cpu(rcu_cpu_has_work, cpu) = 0;
- if (cpu_online(cpu))
- (void)rcu_spawn_one_cpu_kthread(cpu);
- }
- rnp = rcu_get_root(rcu_state);
- init_waitqueue_head(&rnp->node_wq);
- rcu_init_boost_waitqueue(rnp);
- (void)rcu_spawn_one_node_kthread(rcu_state, rnp);
- if (NUM_RCU_NODES > 1)
- rcu_for_each_leaf_node(rcu_state, rnp) {
- init_waitqueue_head(&rnp->node_wq);
- rcu_init_boost_waitqueue(rnp);
- (void)rcu_spawn_one_node_kthread(rcu_state, rnp);
- }
- return 0;
-}
-early_initcall(rcu_spawn_kthreads);
-
static void
__call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu),
- struct rcu_state *rsp)
+ struct rcu_state *rsp, bool lazy)
{
unsigned long flags;
struct rcu_data *rdp;
+ WARN_ON_ONCE((unsigned long)head & 0x3); /* Misaligned rcu_head! */
debug_rcu_head_queue(head);
head->func = func;
head->next = NULL;
/* Add the callback to our list. */
*rdp->nxttail[RCU_NEXT_TAIL] = head;
rdp->nxttail[RCU_NEXT_TAIL] = &head->next;
+ rdp->qlen++;
+ if (lazy)
+ rdp->qlen_lazy++;
+
+ if (__is_kfree_rcu_offset((unsigned long)func))
+ trace_rcu_kfree_callback(rsp->name, head, (unsigned long)func,
+ rdp->qlen_lazy, rdp->qlen);
+ else
+ trace_rcu_callback(rsp->name, head, rdp->qlen_lazy, rdp->qlen);
+
+ /* If interrupts were disabled, don't dive into RCU core. */
+ if (irqs_disabled_flags(flags)) {
+ local_irq_restore(flags);
+ return;
+ }
/*
* Force the grace period if too many callbacks or too long waiting.
* invoking force_quiescent_state() if the newly enqueued callback
* is the only one waiting for a grace period to complete.
*/
- if (unlikely(++rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
+ if (unlikely(rdp->qlen > rdp->qlen_last_fqs_check + qhimark)) {
/* Are we ignoring a completed grace period? */
rcu_process_gp_end(rsp, rdp);
*/
void call_rcu_sched(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
{
- __call_rcu(head, func, &rcu_sched_state);
+ __call_rcu(head, func, &rcu_sched_state, 0);
}
EXPORT_SYMBOL_GPL(call_rcu_sched);
/*
- * Queue an RCU for invocation after a quicker grace period.
+ * Queue an RCU callback for invocation after a quicker grace period.
*/
void call_rcu_bh(struct rcu_head *head, void (*func)(struct rcu_head *rcu))
{
- __call_rcu(head, func, &rcu_bh_state);
+ __call_rcu(head, func, &rcu_bh_state, 0);
}
EXPORT_SYMBOL_GPL(call_rcu_bh);
*/
void synchronize_sched(void)
{
- struct rcu_synchronize rcu;
-
+ rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
+ !lock_is_held(&rcu_lock_map) &&
+ !lock_is_held(&rcu_sched_lock_map),
+ "Illegal synchronize_sched() in RCU-sched read-side critical section");
if (rcu_blocking_is_gp())
return;
-
- init_rcu_head_on_stack(&rcu.head);
- init_completion(&rcu.completion);
- /* Will wake me after RCU finished. */
- call_rcu_sched(&rcu.head, wakeme_after_rcu);
- /* Wait for it. */
- wait_for_completion(&rcu.completion);
- destroy_rcu_head_on_stack(&rcu.head);
+ wait_rcu_gp(call_rcu_sched);
}
EXPORT_SYMBOL_GPL(synchronize_sched);
*/
void synchronize_rcu_bh(void)
{
- struct rcu_synchronize rcu;
-
+ rcu_lockdep_assert(!lock_is_held(&rcu_bh_lock_map) &&
+ !lock_is_held(&rcu_lock_map) &&
+ !lock_is_held(&rcu_sched_lock_map),
+ "Illegal synchronize_rcu_bh() in RCU-bh read-side critical section");
if (rcu_blocking_is_gp())
return;
-
- init_rcu_head_on_stack(&rcu.head);
- init_completion(&rcu.completion);
- /* Will wake me after RCU finished. */
- call_rcu_bh(&rcu.head, wakeme_after_rcu);
- /* Wait for it. */
- wait_for_completion(&rcu.completion);
- destroy_rcu_head_on_stack(&rcu.head);
+ wait_rcu_gp(call_rcu_bh);
}
EXPORT_SYMBOL_GPL(synchronize_rcu_bh);
+static atomic_t sync_sched_expedited_started = ATOMIC_INIT(0);
+static atomic_t sync_sched_expedited_done = ATOMIC_INIT(0);
+
+static int synchronize_sched_expedited_cpu_stop(void *data)
+{
+ /*
+ * There must be a full memory barrier on each affected CPU
+ * between the time that try_stop_cpus() is called and the
+ * time that it returns.
+ *
+ * In the current initial implementation of cpu_stop, the
+ * above condition is already met when the control reaches
+ * this point and the following smp_mb() is not strictly
+ * necessary. Do smp_mb() anyway for documentation and
+ * robustness against future implementation changes.
+ */
+ smp_mb(); /* See above comment block. */
+ return 0;
+}
+
+/**
+ * synchronize_sched_expedited - Brute-force RCU-sched grace period
+ *
+ * Wait for an RCU-sched grace period to elapse, but use a "big hammer"
+ * approach to force the grace period to end quickly. This consumes
+ * significant time on all CPUs and is unfriendly to real-time workloads,
+ * so is thus not recommended for any sort of common-case code. In fact,
+ * if you are using synchronize_sched_expedited() in a loop, please
+ * restructure your code to batch your updates, and then use a single
+ * synchronize_sched() instead.
+ *
+ * Note that it is illegal to call this function while holding any lock
+ * that is acquired by a CPU-hotplug notifier. And yes, it is also illegal
+ * to call this function from a CPU-hotplug notifier. Failing to observe
+ * these restriction will result in deadlock.
+ *
+ * This implementation can be thought of as an application of ticket
+ * locking to RCU, with sync_sched_expedited_started and
+ * sync_sched_expedited_done taking on the roles of the halves
+ * of the ticket-lock word. Each task atomically increments
+ * sync_sched_expedited_started upon entry, snapshotting the old value,
+ * then attempts to stop all the CPUs. If this succeeds, then each
+ * CPU will have executed a context switch, resulting in an RCU-sched
+ * grace period. We are then done, so we use atomic_cmpxchg() to
+ * update sync_sched_expedited_done to match our snapshot -- but
+ * only if someone else has not already advanced past our snapshot.
+ *
+ * On the other hand, if try_stop_cpus() fails, we check the value
+ * of sync_sched_expedited_done. If it has advanced past our
+ * initial snapshot, then someone else must have forced a grace period
+ * some time after we took our snapshot. In this case, our work is
+ * done for us, and we can simply return. Otherwise, we try again,
+ * but keep our initial snapshot for purposes of checking for someone
+ * doing our work for us.
+ *
+ * If we fail too many times in a row, we fall back to synchronize_sched().
+ */
+void synchronize_sched_expedited(void)
+{
+ int firstsnap, s, snap, trycount = 0;
+
+ /* Note that atomic_inc_return() implies full memory barrier. */
+ firstsnap = snap = atomic_inc_return(&sync_sched_expedited_started);
+ get_online_cpus();
+ WARN_ON_ONCE(cpu_is_offline(raw_smp_processor_id()));
+
+ /*
+ * Each pass through the following loop attempts to force a
+ * context switch on each CPU.
+ */
+ while (try_stop_cpus(cpu_online_mask,
+ synchronize_sched_expedited_cpu_stop,
+ NULL) == -EAGAIN) {
+ put_online_cpus();
+
+ /* No joy, try again later. Or just synchronize_sched(). */
+ if (trycount++ < 10)
+ udelay(trycount * num_online_cpus());
+ else {
+ synchronize_sched();
+ return;
+ }
+
+ /* Check to see if someone else did our work for us. */
+ s = atomic_read(&sync_sched_expedited_done);
+ if (UINT_CMP_GE((unsigned)s, (unsigned)firstsnap)) {
+ smp_mb(); /* ensure test happens before caller kfree */
+ return;
+ }
+
+ /*
+ * Refetching sync_sched_expedited_started allows later
+ * callers to piggyback on our grace period. We subtract
+ * 1 to get the same token that the last incrementer got.
+ * We retry after they started, so our grace period works
+ * for them, and they started after our first try, so their
+ * grace period works for us.
+ */
+ get_online_cpus();
+ snap = atomic_read(&sync_sched_expedited_started);
+ smp_mb(); /* ensure read is before try_stop_cpus(). */
+ }
+
+ /*
+ * Everyone up to our most recent fetch is covered by our grace
+ * period. Update the counter, but only if our work is still
+ * relevant -- which it won't be if someone who started later
+ * than we did beat us to the punch.
+ */
+ do {
+ s = atomic_read(&sync_sched_expedited_done);
+ if (UINT_CMP_GE((unsigned)s, (unsigned)snap)) {
+ smp_mb(); /* ensure test happens before caller kfree */
+ break;
+ }
+ } while (atomic_cmpxchg(&sync_sched_expedited_done, s, snap) != s);
+
+ put_online_cpus();
+}
+EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
+
/*
* Check to see if there is any immediate RCU-related work to be done
* by the current CPU, for the specified type of RCU, returning 1 if so.
check_cpu_stall(rsp, rdp);
/* Is the RCU core waiting for a quiescent state from this CPU? */
- if (rdp->qs_pending && !rdp->passed_quiesc) {
+ if (rcu_scheduler_fully_active &&
+ rdp->qs_pending && !rdp->passed_quiesce) {
/*
* If force_quiescent_state() coming soon and this CPU
ULONG_CMP_LT(ACCESS_ONCE(rsp->jiffies_force_qs) - 1,
jiffies))
set_need_resched();
- } else if (rdp->qs_pending && rdp->passed_quiesc) {
+ } else if (rdp->qs_pending && rdp->passed_quiesce) {
rdp->n_rp_report_qs++;
return 1;
}
* by the current CPU, even if none need be done immediately, returning
* 1 if so.
*/
-static int rcu_needs_cpu_quick_check(int cpu)
+static int rcu_cpu_has_callbacks(int cpu)
{
/* RCU callbacks either ready or pending? */
return per_cpu(rcu_sched_data, cpu).nxtlist ||
per_cpu(rcu_bh_data, cpu).nxtlist ||
- rcu_preempt_needs_cpu(cpu);
+ rcu_preempt_cpu_has_callbacks(cpu);
}
static DEFINE_PER_CPU(struct rcu_head, rcu_barrier_head) = {NULL};
rdp->nxtlist = NULL;
for (i = 0; i < RCU_NEXT_SIZE; i++)
rdp->nxttail[i] = &rdp->nxtlist;
+ rdp->qlen_lazy = 0;
rdp->qlen = 0;
-#ifdef CONFIG_NO_HZ
rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
-#endif /* #ifdef CONFIG_NO_HZ */
+ WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE);
+ WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
rdp->cpu = cpu;
+ rdp->rsp = rsp;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
}
/* Set up local state, ensuring consistent view of global state. */
raw_spin_lock_irqsave(&rnp->lock, flags);
- rdp->passed_quiesc = 0; /* We could be racing with new GP, */
- rdp->qs_pending = 1; /* so set up to respond to current GP. */
rdp->beenonline = 1; /* We have now been online. */
rdp->preemptible = preemptible;
rdp->qlen_last_fqs_check = 0;
rdp->n_force_qs_snap = rsp->n_force_qs;
rdp->blimit = blimit;
+ rdp->dynticks->dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
+ atomic_set(&rdp->dynticks->dynticks,
+ (atomic_read(&rdp->dynticks->dynticks) & ~0x1) + 1);
+ rcu_prepare_for_idle_init(cpu);
raw_spin_unlock(&rnp->lock); /* irqs remain disabled. */
/*
rnp->qsmaskinit |= mask;
mask = rnp->grpmask;
if (rnp == rdp->mynode) {
- rdp->gpnum = rnp->completed; /* if GP in progress... */
+ /*
+ * If there is a grace period in progress, we will
+ * set up to wait for it next time we run the
+ * RCU core code.
+ */
+ rdp->gpnum = rnp->completed;
rdp->completed = rnp->completed;
- rdp->passed_quiesc_completed = rnp->completed - 1;
+ 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. */
rnp = rnp->parent;
raw_spin_unlock_irqrestore(&rsp->onofflock, flags);
}
-static void __cpuinit rcu_online_cpu(int cpu)
+static void __cpuinit rcu_prepare_cpu(int cpu)
{
rcu_init_percpu_data(cpu, &rcu_sched_state, 0);
rcu_init_percpu_data(cpu, &rcu_bh_state, 0);
rcu_preempt_init_percpu_data(cpu);
}
-static void __cpuinit rcu_online_kthreads(int cpu)
-{
- struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
- struct rcu_node *rnp = rdp->mynode;
-
- /* Fire up the incoming CPU's kthread and leaf rcu_node kthread. */
- if (rcu_kthreads_spawnable) {
- (void)rcu_spawn_one_cpu_kthread(cpu);
- if (rnp->node_kthread_task == NULL)
- (void)rcu_spawn_one_node_kthread(rcu_state, rnp);
- }
-}
-
/*
* Handle CPU online/offline notification events.
*/
struct rcu_data *rdp = per_cpu_ptr(rcu_state->rda, cpu);
struct rcu_node *rnp = rdp->mynode;
+ trace_rcu_utilization("Start CPU hotplug");
switch (action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
- rcu_online_cpu(cpu);
- rcu_online_kthreads(cpu);
+ rcu_prepare_cpu(cpu);
+ rcu_prepare_kthreads(cpu);
break;
case CPU_ONLINE:
case CPU_DOWN_FAILED:
* touch any data without introducing corruption. We send the
* dying CPU's callbacks to an arbitrarily chosen online CPU.
*/
- rcu_send_cbs_to_online(&rcu_bh_state);
- rcu_send_cbs_to_online(&rcu_sched_state);
- rcu_preempt_send_cbs_to_online();
+ rcu_cleanup_dying_cpu(&rcu_bh_state);
+ rcu_cleanup_dying_cpu(&rcu_sched_state);
+ rcu_preempt_cleanup_dying_cpu();
+ rcu_cleanup_after_idle(cpu);
break;
case CPU_DEAD:
case CPU_DEAD_FROZEN:
case CPU_UP_CANCELED:
case CPU_UP_CANCELED_FROZEN:
- rcu_offline_cpu(cpu);
+ rcu_cleanup_dead_cpu(cpu, &rcu_bh_state);
+ rcu_cleanup_dead_cpu(cpu, &rcu_sched_state);
+ rcu_preempt_cleanup_dead_cpu(cpu);
break;
default:
break;
}
+ trace_rcu_utilization("End CPU hotplug");
return NOTIFY_OK;
}
rcu_init_one(&rcu_sched_state, &rcu_sched_data);
rcu_init_one(&rcu_bh_state, &rcu_bh_data);
__rcu_init_preempt();
+ open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
/*
* We don't need protection against CPU-hotplug here because
projects / linux-flexiantxendom0-3.2.10.git / blobdiff