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-rw-r--r--kernel/context_tracking.c75
-rw-r--r--kernel/rcu.h7
-rw-r--r--kernel/rcupdate.c60
-rw-r--r--kernel/rcutiny.c8
-rw-r--r--kernel/rcutiny_plugin.h56
-rw-r--r--kernel/rcutorture.c57
-rw-r--r--kernel/rcutree.c260
-rw-r--r--kernel/rcutree.h11
-rw-r--r--kernel/rcutree_plugin.h13
-rw-r--r--kernel/trace/trace_clock.c1
10 files changed, 431 insertions, 117 deletions
diff --git a/kernel/context_tracking.c b/kernel/context_tracking.c
index e0e07fd5550..d566aba7e80 100644
--- a/kernel/context_tracking.c
+++ b/kernel/context_tracking.c
@@ -1,3 +1,19 @@
+/*
+ * Context tracking: Probe on high level context boundaries such as kernel
+ * and userspace. This includes syscalls and exceptions entry/exit.
+ *
+ * This is used by RCU to remove its dependency on the timer tick while a CPU
+ * runs in userspace.
+ *
+ * Started by Frederic Weisbecker:
+ *
+ * Copyright (C) 2012 Red Hat, Inc., Frederic Weisbecker <fweisbec@redhat.com>
+ *
+ * Many thanks to Gilad Ben-Yossef, Paul McKenney, Ingo Molnar, Andrew Morton,
+ * Steven Rostedt, Peter Zijlstra for suggestions and improvements.
+ *
+ */
+
#include <linux/context_tracking.h>
#include <linux/rcupdate.h>
#include <linux/sched.h>
@@ -6,8 +22,8 @@
struct context_tracking {
/*
- * When active is false, hooks are not set to
- * minimize overhead: TIF flags are cleared
+ * When active is false, probes are unset in order
+ * to minimize overhead: TIF flags are cleared
* and calls to user_enter/exit are ignored. This
* may be further optimized using static keys.
*/
@@ -24,6 +40,15 @@ static DEFINE_PER_CPU(struct context_tracking, context_tracking) = {
#endif
};
+/**
+ * user_enter - Inform the context tracking that the CPU is going to
+ * enter userspace mode.
+ *
+ * This function must be called right before we switch from the kernel
+ * to userspace, when it's guaranteed the remaining kernel instructions
+ * to execute won't use any RCU read side critical section because this
+ * function sets RCU in extended quiescent state.
+ */
void user_enter(void)
{
unsigned long flags;
@@ -39,40 +64,70 @@ void user_enter(void)
if (in_interrupt())
return;
+ /* Kernel threads aren't supposed to go to userspace */
WARN_ON_ONCE(!current->mm);
local_irq_save(flags);
if (__this_cpu_read(context_tracking.active) &&
__this_cpu_read(context_tracking.state) != IN_USER) {
__this_cpu_write(context_tracking.state, IN_USER);
+ /*
+ * At this stage, only low level arch entry code remains and
+ * then we'll run in userspace. We can assume there won't be
+ * any RCU read-side critical section until the next call to
+ * user_exit() or rcu_irq_enter(). Let's remove RCU's dependency
+ * on the tick.
+ */
rcu_user_enter();
}
local_irq_restore(flags);
}
+
+/**
+ * user_exit - Inform the context tracking that the CPU is
+ * exiting userspace mode and entering the kernel.
+ *
+ * This function must be called after we entered the kernel from userspace
+ * before any use of RCU read side critical section. This potentially include
+ * any high level kernel code like syscalls, exceptions, signal handling, etc...
+ *
+ * This call supports re-entrancy. This way it can be called from any exception
+ * handler without needing to know if we came from userspace or not.
+ */
void user_exit(void)
{
unsigned long flags;
- /*
- * Some contexts may involve an exception occuring in an irq,
- * leading to that nesting:
- * rcu_irq_enter() rcu_user_exit() rcu_user_exit() rcu_irq_exit()
- * This would mess up the dyntick_nesting count though. And rcu_irq_*()
- * helpers are enough to protect RCU uses inside the exception. So
- * just return immediately if we detect we are in an IRQ.
- */
if (in_interrupt())
return;
local_irq_save(flags);
if (__this_cpu_read(context_tracking.state) == IN_USER) {
__this_cpu_write(context_tracking.state, IN_KERNEL);
+ /*
+ * We are going to run code that may use RCU. Inform
+ * RCU core about that (ie: we may need the tick again).
+ */
rcu_user_exit();
}
local_irq_restore(flags);
}
+
+/**
+ * context_tracking_task_switch - context switch the syscall callbacks
+ * @prev: the task that is being switched out
+ * @next: the task that is being switched in
+ *
+ * The context tracking uses the syscall slow path to implement its user-kernel
+ * boundaries probes on syscalls. This way it doesn't impact the syscall fast
+ * path on CPUs that don't do context tracking.
+ *
+ * But we need to clear the flag on the previous task because it may later
+ * migrate to some CPU that doesn't do the context tracking. As such the TIF
+ * flag may not be desired there.
+ */
void context_tracking_task_switch(struct task_struct *prev,
struct task_struct *next)
{
diff --git a/kernel/rcu.h b/kernel/rcu.h
index 20dfba576c2..7f8e7590e3e 100644
--- a/kernel/rcu.h
+++ b/kernel/rcu.h
@@ -111,4 +111,11 @@ static inline bool __rcu_reclaim(char *rn, struct rcu_head *head)
extern int rcu_expedited;
+#ifdef CONFIG_RCU_STALL_COMMON
+
+extern int rcu_cpu_stall_suppress;
+int rcu_jiffies_till_stall_check(void);
+
+#endif /* #ifdef CONFIG_RCU_STALL_COMMON */
+
#endif /* __LINUX_RCU_H */
diff --git a/kernel/rcupdate.c b/kernel/rcupdate.c
index a2cf76177b4..48ab70384a4 100644
--- a/kernel/rcupdate.c
+++ b/kernel/rcupdate.c
@@ -404,11 +404,65 @@ EXPORT_SYMBOL_GPL(rcuhead_debug_descr);
#endif /* #ifdef CONFIG_DEBUG_OBJECTS_RCU_HEAD */
#if defined(CONFIG_TREE_RCU) || defined(CONFIG_TREE_PREEMPT_RCU) || defined(CONFIG_RCU_TRACE)
-void do_trace_rcu_torture_read(char *rcutorturename, struct rcu_head *rhp)
+void do_trace_rcu_torture_read(char *rcutorturename, struct rcu_head *rhp,
+ unsigned long secs,
+ unsigned long c_old, unsigned long c)
{
- trace_rcu_torture_read(rcutorturename, rhp);
+ trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c);
}
EXPORT_SYMBOL_GPL(do_trace_rcu_torture_read);
#else
-#define do_trace_rcu_torture_read(rcutorturename, rhp) do { } while (0)
+#define do_trace_rcu_torture_read(rcutorturename, rhp, secs, c_old, c) \
+ do { } while (0)
#endif
+
+#ifdef CONFIG_RCU_STALL_COMMON
+
+#ifdef CONFIG_PROVE_RCU
+#define RCU_STALL_DELAY_DELTA (5 * HZ)
+#else
+#define RCU_STALL_DELAY_DELTA 0
+#endif
+
+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);
+
+int rcu_jiffies_till_stall_check(void)
+{
+ int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout);
+
+ /*
+ * 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;
+}
+
+static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
+{
+ rcu_cpu_stall_suppress = 1;
+ return NOTIFY_DONE;
+}
+
+static struct notifier_block rcu_panic_block = {
+ .notifier_call = rcu_panic,
+};
+
+static int __init check_cpu_stall_init(void)
+{
+ atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
+ return 0;
+}
+early_initcall(check_cpu_stall_init);
+
+#endif /* #ifdef CONFIG_RCU_STALL_COMMON */
diff --git a/kernel/rcutiny.c b/kernel/rcutiny.c
index e7dce58f9c2..a0714a51b6d 100644
--- a/kernel/rcutiny.c
+++ b/kernel/rcutiny.c
@@ -51,10 +51,10 @@ static void __call_rcu(struct rcu_head *head,
void (*func)(struct rcu_head *rcu),
struct rcu_ctrlblk *rcp);
-#include "rcutiny_plugin.h"
-
static long long rcu_dynticks_nesting = DYNTICK_TASK_EXIT_IDLE;
+#include "rcutiny_plugin.h"
+
/* Common code for rcu_idle_enter() and rcu_irq_exit(), see kernel/rcutree.c. */
static void rcu_idle_enter_common(long long newval)
{
@@ -193,7 +193,7 @@ EXPORT_SYMBOL(rcu_is_cpu_idle);
* interrupts don't count, we must be running at the first interrupt
* level.
*/
-int rcu_is_cpu_rrupt_from_idle(void)
+static int rcu_is_cpu_rrupt_from_idle(void)
{
return rcu_dynticks_nesting <= 1;
}
@@ -205,6 +205,7 @@ int rcu_is_cpu_rrupt_from_idle(void)
*/
static int rcu_qsctr_help(struct rcu_ctrlblk *rcp)
{
+ reset_cpu_stall_ticks(rcp);
if (rcp->rcucblist != NULL &&
rcp->donetail != rcp->curtail) {
rcp->donetail = rcp->curtail;
@@ -251,6 +252,7 @@ void rcu_bh_qs(int cpu)
*/
void rcu_check_callbacks(int cpu, int user)
{
+ check_cpu_stalls();
if (user || rcu_is_cpu_rrupt_from_idle())
rcu_sched_qs(cpu);
else if (!in_softirq())
diff --git a/kernel/rcutiny_plugin.h b/kernel/rcutiny_plugin.h
index f85016a2309..8a233002fae 100644
--- a/kernel/rcutiny_plugin.h
+++ b/kernel/rcutiny_plugin.h
@@ -33,6 +33,9 @@ struct rcu_ctrlblk {
struct rcu_head **donetail; /* ->next pointer of last "done" CB. */
struct rcu_head **curtail; /* ->next pointer of last CB. */
RCU_TRACE(long qlen); /* Number of pending CBs. */
+ RCU_TRACE(unsigned long gp_start); /* Start time for stalls. */
+ RCU_TRACE(unsigned long ticks_this_gp); /* Statistic for stalls. */
+ RCU_TRACE(unsigned long jiffies_stall); /* Jiffies at next stall. */
RCU_TRACE(char *name); /* Name of RCU type. */
};
@@ -54,6 +57,51 @@ int rcu_scheduler_active __read_mostly;
EXPORT_SYMBOL_GPL(rcu_scheduler_active);
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
+#ifdef CONFIG_RCU_TRACE
+
+static void check_cpu_stall(struct rcu_ctrlblk *rcp)
+{
+ unsigned long j;
+ unsigned long js;
+
+ if (rcu_cpu_stall_suppress)
+ return;
+ rcp->ticks_this_gp++;
+ j = jiffies;
+ js = rcp->jiffies_stall;
+ if (*rcp->curtail && ULONG_CMP_GE(j, js)) {
+ pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n",
+ rcp->name, rcp->ticks_this_gp, rcu_dynticks_nesting,
+ jiffies - rcp->gp_start, rcp->qlen);
+ dump_stack();
+ }
+ if (*rcp->curtail && ULONG_CMP_GE(j, js))
+ rcp->jiffies_stall = jiffies +
+ 3 * rcu_jiffies_till_stall_check() + 3;
+ else if (ULONG_CMP_GE(j, js))
+ rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
+}
+
+static void check_cpu_stall_preempt(void);
+
+#endif /* #ifdef CONFIG_RCU_TRACE */
+
+static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)
+{
+#ifdef CONFIG_RCU_TRACE
+ rcp->ticks_this_gp = 0;
+ rcp->gp_start = jiffies;
+ rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
+#endif /* #ifdef CONFIG_RCU_TRACE */
+}
+
+static void check_cpu_stalls(void)
+{
+ RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk));
+ RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk));
+ RCU_TRACE(check_cpu_stall_preempt());
+}
+
#ifdef CONFIG_TINY_PREEMPT_RCU
#include <linux/delay.h>
@@ -448,6 +496,7 @@ static void rcu_preempt_start_gp(void)
/* Official start of GP. */
rcu_preempt_ctrlblk.gpnum++;
RCU_TRACE(rcu_preempt_ctrlblk.n_grace_periods++);
+ reset_cpu_stall_ticks(&rcu_preempt_ctrlblk.rcb);
/* Any blocked RCU readers block new GP. */
if (rcu_preempt_blocked_readers_any())
@@ -1054,4 +1103,11 @@ MODULE_AUTHOR("Paul E. McKenney");
MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation");
MODULE_LICENSE("GPL");
+static void check_cpu_stall_preempt(void)
+{
+#ifdef CONFIG_TINY_PREEMPT_RCU
+ check_cpu_stall(&rcu_preempt_ctrlblk.rcb);
+#endif /* #ifdef CONFIG_TINY_PREEMPT_RCU */
+}
+
#endif /* #ifdef CONFIG_RCU_TRACE */
diff --git a/kernel/rcutorture.c b/kernel/rcutorture.c
index 31dea01c85f..cd4c35d097a 100644
--- a/kernel/rcutorture.c
+++ b/kernel/rcutorture.c
@@ -46,6 +46,7 @@
#include <linux/stat.h>
#include <linux/srcu.h>
#include <linux/slab.h>
+#include <linux/trace_clock.h>
#include <asm/byteorder.h>
MODULE_LICENSE("GPL");
@@ -845,7 +846,7 @@ static int rcu_torture_boost(void *arg)
/* Wait for the next test interval. */
oldstarttime = boost_starttime;
while (ULONG_CMP_LT(jiffies, oldstarttime)) {
- schedule_timeout_uninterruptible(1);
+ schedule_timeout_interruptible(oldstarttime - jiffies);
rcu_stutter_wait("rcu_torture_boost");
if (kthread_should_stop() ||
fullstop != FULLSTOP_DONTSTOP)
@@ -1028,7 +1029,6 @@ void rcutorture_trace_dump(void)
return;
if (atomic_xchg(&beenhere, 1) != 0)
return;
- do_trace_rcu_torture_read(cur_ops->name, (struct rcu_head *)~0UL);
ftrace_dump(DUMP_ALL);
}
@@ -1042,13 +1042,16 @@ static void rcu_torture_timer(unsigned long unused)
{
int idx;
int completed;
+ int completed_end;
static DEFINE_RCU_RANDOM(rand);
static DEFINE_SPINLOCK(rand_lock);
struct rcu_torture *p;
int pipe_count;
+ unsigned long long ts;
idx = cur_ops->readlock();
completed = cur_ops->completed();
+ ts = trace_clock_local();
p = rcu_dereference_check(rcu_torture_current,
rcu_read_lock_bh_held() ||
rcu_read_lock_sched_held() ||
@@ -1058,7 +1061,6 @@ static void rcu_torture_timer(unsigned long unused)
cur_ops->readunlock(idx);
return;
}
- do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu);
if (p->rtort_mbtest == 0)
atomic_inc(&n_rcu_torture_mberror);
spin_lock(&rand_lock);
@@ -1071,10 +1073,16 @@ static void rcu_torture_timer(unsigned long unused)
/* Should not happen, but... */
pipe_count = RCU_TORTURE_PIPE_LEN;
}
- if (pipe_count > 1)
+ completed_end = cur_ops->completed();
+ if (pipe_count > 1) {
+ unsigned long __maybe_unused ts_rem = do_div(ts, NSEC_PER_USEC);
+
+ do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu, ts,
+ completed, completed_end);
rcutorture_trace_dump();
+ }
__this_cpu_inc(rcu_torture_count[pipe_count]);
- completed = cur_ops->completed() - completed;
+ completed = completed_end - completed;
if (completed > RCU_TORTURE_PIPE_LEN) {
/* Should not happen, but... */
completed = RCU_TORTURE_PIPE_LEN;
@@ -1094,11 +1102,13 @@ static int
rcu_torture_reader(void *arg)
{
int completed;
+ int completed_end;
int idx;
DEFINE_RCU_RANDOM(rand);
struct rcu_torture *p;
int pipe_count;
struct timer_list t;
+ unsigned long long ts;
VERBOSE_PRINTK_STRING("rcu_torture_reader task started");
set_user_nice(current, 19);
@@ -1112,6 +1122,7 @@ rcu_torture_reader(void *arg)
}
idx = cur_ops->readlock();
completed = cur_ops->completed();
+ ts = trace_clock_local();
p = rcu_dereference_check(rcu_torture_current,
rcu_read_lock_bh_held() ||
rcu_read_lock_sched_held() ||
@@ -1122,7 +1133,6 @@ rcu_torture_reader(void *arg)
schedule_timeout_interruptible(HZ);
continue;
}
- do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu);
if (p->rtort_mbtest == 0)
atomic_inc(&n_rcu_torture_mberror);
cur_ops->read_delay(&rand);
@@ -1132,10 +1142,17 @@ rcu_torture_reader(void *arg)
/* Should not happen, but... */
pipe_count = RCU_TORTURE_PIPE_LEN;
}
- if (pipe_count > 1)
+ completed_end = cur_ops->completed();
+ if (pipe_count > 1) {
+ unsigned long __maybe_unused ts_rem =
+ do_div(ts, NSEC_PER_USEC);
+
+ do_trace_rcu_torture_read(cur_ops->name, &p->rtort_rcu,
+ ts, completed, completed_end);
rcutorture_trace_dump();
+ }
__this_cpu_inc(rcu_torture_count[pipe_count]);
- completed = cur_ops->completed() - completed;
+ completed = completed_end - completed;
if (completed > RCU_TORTURE_PIPE_LEN) {
/* Should not happen, but... */
completed = RCU_TORTURE_PIPE_LEN;
@@ -1301,19 +1318,35 @@ static void rcu_torture_shuffle_tasks(void)
set_cpus_allowed_ptr(reader_tasks[i],
shuffle_tmp_mask);
}
-
if (fakewriter_tasks) {
for (i = 0; i < nfakewriters; i++)
if (fakewriter_tasks[i])
set_cpus_allowed_ptr(fakewriter_tasks[i],
shuffle_tmp_mask);
}
-
if (writer_task)
set_cpus_allowed_ptr(writer_task, shuffle_tmp_mask);
-
if (stats_task)
set_cpus_allowed_ptr(stats_task, shuffle_tmp_mask);
+ if (stutter_task)
+ set_cpus_allowed_ptr(stutter_task, shuffle_tmp_mask);
+ if (fqs_task)
+ set_cpus_allowed_ptr(fqs_task, shuffle_tmp_mask);
+ if (shutdown_task)
+ set_cpus_allowed_ptr(shutdown_task, shuffle_tmp_mask);
+#ifdef CONFIG_HOTPLUG_CPU
+ if (onoff_task)
+ set_cpus_allowed_ptr(onoff_task, shuffle_tmp_mask);
+#endif /* #ifdef CONFIG_HOTPLUG_CPU */
+ if (stall_task)
+ set_cpus_allowed_ptr(stall_task, shuffle_tmp_mask);
+ if (barrier_cbs_tasks)
+ for (i = 0; i < n_barrier_cbs; i++)
+ if (barrier_cbs_tasks[i])
+ set_cpus_allowed_ptr(barrier_cbs_tasks[i],
+ shuffle_tmp_mask);
+ if (barrier_task)
+ set_cpus_allowed_ptr(barrier_task, shuffle_tmp_mask);
if (rcu_idle_cpu == -1)
rcu_idle_cpu = num_online_cpus() - 1;
@@ -1749,7 +1782,7 @@ static int rcu_torture_barrier_init(void)
barrier_cbs_wq =
kzalloc(n_barrier_cbs * sizeof(barrier_cbs_wq[0]),
GFP_KERNEL);
- if (barrier_cbs_tasks == NULL || barrier_cbs_wq == 0)
+ if (barrier_cbs_tasks == NULL || !barrier_cbs_wq)
return -ENOMEM;
for (i = 0; i < n_barrier_cbs; i++) {
init_waitqueue_head(&barrier_cbs_wq[i]);
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index e441b77b614..5b8ad827fd8 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -105,7 +105,7 @@ int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */
* 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
+ * optimize 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.
@@ -217,12 +217,6 @@ module_param(blimit, long, 0444);
module_param(qhimark, long, 0444);
module_param(qlowmark, long, 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 ulong jiffies_till_first_fqs = RCU_JIFFIES_TILL_FORCE_QS;
static ulong jiffies_till_next_fqs = RCU_JIFFIES_TILL_FORCE_QS;
@@ -305,17 +299,27 @@ cpu_has_callbacks_ready_to_invoke(struct rcu_data *rdp)
}
/*
- * Does the current CPU require a yet-as-unscheduled grace period?
+ * Does the current CPU require a not-yet-started grace period?
+ * The caller must have disabled interrupts to prevent races with
+ * normal callback registry.
*/
static int
cpu_needs_another_gp(struct rcu_state *rsp, struct rcu_data *rdp)
{
- struct rcu_head **ntp;
+ int i;
- ntp = rdp->nxttail[RCU_DONE_TAIL +
- (ACCESS_ONCE(rsp->completed) != rdp->completed)];
- return rdp->nxttail[RCU_DONE_TAIL] && ntp && *ntp &&
- !rcu_gp_in_progress(rsp);
+ if (rcu_gp_in_progress(rsp))
+ return 0; /* No, a grace period is already in progress. */
+ if (!rdp->nxttail[RCU_NEXT_TAIL])
+ return 0; /* No, this is a no-CBs (or offline) CPU. */
+ if (*rdp->nxttail[RCU_NEXT_READY_TAIL])
+ return 1; /* Yes, this CPU has newly registered callbacks. */
+ for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++)
+ if (rdp->nxttail[i - 1] != rdp->nxttail[i] &&
+ ULONG_CMP_LT(ACCESS_ONCE(rsp->completed),
+ rdp->nxtcompleted[i]))
+ return 1; /* Yes, CBs for future grace period. */
+ return 0; /* No grace period needed. */
}
/*
@@ -336,7 +340,7 @@ static struct rcu_node *rcu_get_root(struct rcu_state *rsp)
static void rcu_eqs_enter_common(struct rcu_dynticks *rdtp, long long oldval,
bool user)
{
- trace_rcu_dyntick("Start", oldval, 0);
+ trace_rcu_dyntick("Start", oldval, rdtp->dynticks_nesting);
if (!user && !is_idle_task(current)) {
struct task_struct *idle = idle_task(smp_processor_id());
@@ -727,7 +731,7 @@ EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online);
* interrupt from idle, return true. The caller must have at least
* disabled preemption.
*/
-int rcu_is_cpu_rrupt_from_idle(void)
+static int rcu_is_cpu_rrupt_from_idle(void)
{
return __get_cpu_var(rcu_dynticks).dynticks_nesting <= 1;
}
@@ -793,28 +797,10 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
return 0;
}
-static int jiffies_till_stall_check(void)
-{
- int till_stall_check = ACCESS_ONCE(rcu_cpu_stall_timeout);
-
- /*
- * 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;
-}
-
static void record_gp_stall_check_time(struct rcu_state *rsp)
{
rsp->gp_start = jiffies;
- rsp->jiffies_stall = jiffies + jiffies_till_stall_check();
+ rsp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
}
/*
@@ -857,7 +843,7 @@ static void print_other_cpu_stall(struct rcu_state *rsp)
raw_spin_unlock_irqrestore(&rnp->lock, flags);
return;
}
- rsp->jiffies_stall = jiffies + 3 * jiffies_till_stall_check() + 3;
+ rsp->jiffies_stall = jiffies + 3 * rcu_jiffies_till_stall_check() + 3;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
/*
@@ -935,7 +921,7 @@ static void print_cpu_stall(struct rcu_state *rsp)
raw_spin_lock_irqsave(&rnp->lock, flags);
if (ULONG_CMP_GE(jiffies, rsp->jiffies_stall))
rsp->jiffies_stall = jiffies +
- 3 * jiffies_till_stall_check() + 3;
+ 3 * rcu_jiffies_till_stall_check() + 3;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
set_need_resched(); /* kick ourselves to get things going. */
@@ -966,12 +952,6 @@ static void check_cpu_stall(struct rcu_state *rsp, struct rcu_data *rdp)
}
}
-static int rcu_panic(struct notifier_block *this, unsigned long ev, void *ptr)
-{
- rcu_cpu_stall_suppress = 1;
- return NOTIFY_DONE;
-}
-
/**
* rcu_cpu_stall_reset - prevent further stall warnings in current grace period
*
@@ -989,15 +969,6 @@ void rcu_cpu_stall_reset(void)
rsp->jiffies_stall = jiffies + ULONG_MAX / 2;
}
-static struct notifier_block rcu_panic_block = {
- .notifier_call = rcu_panic,
-};
-
-static void __init check_cpu_stall_init(void)
-{
- atomic_notifier_chain_register(&panic_notifier_list, &rcu_panic_block);
-}
-
/*
* Update CPU-local rcu_data state to record the newly noticed grace period.
* This is used both when we started the grace period and when we notice
@@ -1071,6 +1042,145 @@ static void init_callback_list(struct rcu_data *rdp)
}
/*
+ * Determine the value that ->completed will have at the end of the
+ * next subsequent grace period. This is used to tag callbacks so that
+ * a CPU can invoke callbacks in a timely fashion even if that CPU has
+ * been dyntick-idle for an extended period with callbacks under the
+ * influence of RCU_FAST_NO_HZ.
+ *
+ * The caller must hold rnp->lock with interrupts disabled.
+ */
+static unsigned long rcu_cbs_completed(struct rcu_state *rsp,
+ struct rcu_node *rnp)
+{
+ /*
+ * If RCU is idle, we just wait for the next grace period.
+ * But we can only be sure that RCU is idle if we are looking
+ * at the root rcu_node structure -- otherwise, a new grace
+ * period might have started, but just not yet gotten around
+ * to initializing the current non-root rcu_node structure.
+ */
+ if (rcu_get_root(rsp) == rnp && rnp->gpnum == rnp->completed)
+ return rnp->completed + 1;
+
+ /*
+ * Otherwise, wait for a possible partial grace period and
+ * then the subsequent full grace period.
+ */
+ return rnp->completed + 2;
+}
+
+/*
+ * If there is room, assign a ->completed number to any callbacks on
+ * this CPU that have not already been assigned. Also accelerate any
+ * callbacks that were previously assigned a ->completed number that has
+ * since proven to be too conservative, which can happen if callbacks get
+ * assigned a ->completed number while RCU is idle, but with reference to
+ * a non-root rcu_node structure. This function is idempotent, so it does
+ * not hurt to call it repeatedly.
+ *
+ * The caller must hold rnp->lock with interrupts disabled.
+ */
+static void rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
+ struct rcu_data *rdp)
+{
+ unsigned long c;
+ int i;
+
+ /* If the CPU has no callbacks, nothing to do. */
+ if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL])
+ return;
+
+ /*
+ * Starting from the sublist containing the callbacks most
+ * recently assigned a ->completed number and working down, find the
+ * first sublist that is not assignable to an upcoming grace period.
+ * Such a sublist has something in it (first two tests) and has
+ * a ->completed number assigned that will complete sooner than
+ * the ->completed number for newly arrived callbacks (last test).
+ *
+ * The key point is that any later sublist can be assigned the
+ * same ->completed number as the newly arrived callbacks, which
+ * means that the callbacks in any of these later sublist can be
+ * grouped into a single sublist, whether or not they have already
+ * been assigned a ->completed number.
+ */
+ c = rcu_cbs_completed(rsp, rnp);
+ for (i = RCU_NEXT_TAIL - 1; i > RCU_DONE_TAIL; i--)
+ if (rdp->nxttail[i] != rdp->nxttail[i - 1] &&
+ !ULONG_CMP_GE(rdp->nxtcompleted[i], c))
+ break;
+
+ /*
+ * If there are no sublist for unassigned callbacks, leave.
+ * At the same time, advance "i" one sublist, so that "i" will
+ * index into the sublist where all the remaining callbacks should
+ * be grouped into.
+ */
+ if (++i >= RCU_NEXT_TAIL)
+ return;
+
+ /*
+ * Assign all subsequent callbacks' ->completed number to the next
+ * full grace period and group them all in the sublist initially
+ * indexed by "i".
+ */
+ for (; i <= RCU_NEXT_TAIL; i++) {
+ rdp->nxttail[i] = rdp->nxttail[RCU_NEXT_TAIL];
+ rdp->nxtcompleted[i] = c;
+ }
+
+ /* Trace depending on how much we were able to accelerate. */
+ if (!*rdp->nxttail[RCU_WAIT_TAIL])
+ trace_rcu_grace_period(rsp->name, rdp->gpnum, "AccWaitCB");
+ else
+ trace_rcu_grace_period(rsp->name, rdp->gpnum, "AccReadyCB");
+}
+
+/*
+ * Move any callbacks whose grace period has completed to the
+ * RCU_DONE_TAIL sublist, then compact the remaining sublists and
+ * assign ->completed numbers to any callbacks in the RCU_NEXT_TAIL
+ * sublist. This function is idempotent, so it does not hurt to
+ * invoke it repeatedly. As long as it is not invoked -too- often...
+ *
+ * The caller must hold rnp->lock with interrupts disabled.
+ */
+static void rcu_advance_cbs(struct rcu_state *rsp, struct rcu_node *rnp,
+ struct rcu_data *rdp)
+{
+ int i, j;
+
+ /* If the CPU has no callbacks, nothing to do. */
+ if (!rdp->nxttail[RCU_NEXT_TAIL] || !*rdp->nxttail[RCU_DONE_TAIL])
+ return;
+
+ /*
+ * Find all callbacks whose ->completed numbers indicate that they
+ * are ready to invoke, and put them into the RCU_DONE_TAIL sublist.
+ */
+ for (i = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++) {
+ if (ULONG_CMP_LT(rnp->completed, rdp->nxtcompleted[i]))
+ break;
+ rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[i];
+ }
+ /* Clean up any sublist tail pointers that were misordered above. */
+ for (j = RCU_WAIT_TAIL; j < i; j++)
+ rdp->nxttail[j] = rdp->nxttail[RCU_DONE_TAIL];
+
+ /* Copy down callbacks to fill in empty sublists. */
+ for (j = RCU_WAIT_TAIL; i < RCU_NEXT_TAIL; i++, j++) {
+ if (rdp->nxttail[j] == rdp->nxttail[RCU_NEXT_TAIL])
+ break;
+ rdp->nxttail[j] = rdp->nxttail[i];
+ rdp->nxtcompleted[j] = rdp->nxtcompleted[i];
+ }
+
+ /* Classify any remaining callbacks. */
+ rcu_accelerate_cbs(rsp, rnp, rdp);
+}
+
+/*
* Advance this CPU's callbacks, but only if the current grace period
* has ended. This may be called only from the CPU to whom the rdp
* belongs. In addition, the corresponding leaf rcu_node structure's
@@ -1080,12 +1190,15 @@ static void
__rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
{
/* Did another grace period end? */
- if (rdp->completed != rnp->completed) {
+ if (rdp->completed == rnp->completed) {
- /* Advance callbacks. No harm if list empty. */
- rdp->nxttail[RCU_DONE_TAIL] = rdp->nxttail[RCU_WAIT_TAIL];
- rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_READY_TAIL];
- rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
+ /* No, so just accelerate recent callbacks. */
+ rcu_accelerate_cbs(rsp, rnp, rdp);
+
+ } else {
+
+ /* Advance callbacks. */
+ rcu_advance_cbs(rsp, rnp, rdp);
/* Remember that we saw this grace-period completion. */
rdp->completed = rnp->completed;
@@ -1392,17 +1505,10 @@ rcu_start_gp(struct rcu_state *rsp, unsigned long flags)
/*
* Because there is no grace period in progress right now,
* any callbacks we have up to this point will be satisfied
- * by the next grace period. So promote all callbacks to be
- * handled after the end of the next grace period. If the
- * CPU is not yet aware of the end of the previous grace period,
- * we need to allow for the callback advancement that will
- * occur when it does become aware. Deadlock prevents us from
- * making it aware at this point: We cannot acquire a leaf
- * rcu_node ->lock while holding the root rcu_node ->lock.
+ * by the next grace period. So this is a good place to
+ * assign a grace period number to recently posted callbacks.
*/
- rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
- if (rdp->completed == rsp->completed)
- rdp->nxttail[RCU_WAIT_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
+ rcu_accelerate_cbs(rsp, rnp, rdp);
rsp->gp_flags = RCU_GP_FLAG_INIT;
raw_spin_unlock(&rnp->lock); /* Interrupts remain disabled. */
@@ -1527,7 +1633,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp)
* This GP can't end until cpu checks in, so all of our
* callbacks can be processed during the next GP.
*/
- rdp->nxttail[RCU_NEXT_READY_TAIL] = rdp->nxttail[RCU_NEXT_TAIL];
+ rcu_accelerate_cbs(rsp, rnp, rdp);
rcu_report_qs_rnp(mask, rsp, rnp, flags); /* rlses rnp->lock */
}
@@ -1779,7 +1885,7 @@ static void rcu_do_batch(struct rcu_state *rsp, struct rcu_data *rdp)
long bl, count, count_lazy;
int i;
- /* If no callbacks are ready, just return.*/
+ /* If no callbacks are ready, just return. */
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),
@@ -2008,19 +2114,19 @@ __rcu_process_callbacks(struct rcu_state *rsp)
WARN_ON_ONCE(rdp->beenonline == 0);
- /*
- * Advance callbacks in response to end of earlier grace
- * period that some other CPU ended.
- */
+ /* Handle the end of a grace period that some other CPU ended. */
rcu_process_gp_end(rsp, rdp);
/* Update RCU state based on any recent quiescent states. */
rcu_check_quiescent_state(rsp, rdp);
/* Does this CPU require a not-yet-started grace period? */
+ local_irq_save(flags);
if (cpu_needs_another_gp(rsp, rdp)) {
- raw_spin_lock_irqsave(&rcu_get_root(rsp)->lock, flags);
+ raw_spin_lock(&rcu_get_root(rsp)->lock); /* irqs disabled. */
rcu_start_gp(rsp, flags); /* releases above lock */
+ } else {
+ local_irq_restore(flags);
}
/* If there are callbacks ready, invoke them. */
@@ -2719,9 +2825,6 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
rdp->dynticks = &per_cpu(rcu_dynticks, cpu);
WARN_ON_ONCE(rdp->dynticks->dynticks_nesting != DYNTICK_TASK_EXIT_IDLE);
WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
-#ifdef CONFIG_RCU_USER_QS
- WARN_ON_ONCE(rdp->dynticks->in_user);
-#endif
rdp->cpu = cpu;
rdp->rsp = rsp;
rcu_boot_init_nocb_percpu_data(rdp);
@@ -2938,6 +3041,10 @@ static void __init rcu_init_one(struct rcu_state *rsp,
BUILD_BUG_ON(MAX_RCU_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */
+ /* Silence gcc 4.8 warning about array index out of range. */
+ if (rcu_num_lvls > RCU_NUM_LVLS)
+ panic("rcu_init_one: rcu_num_lvls overflow");
+
/* Initialize the level-tracking arrays. */
for (i = 0; i < rcu_num_lvls; i++)
@@ -3074,7 +3181,6 @@ void __init rcu_init(void)
cpu_notifier(rcu_cpu_notify, 0);
for_each_online_cpu(cpu)
rcu_cpu_notify(NULL, CPU_UP_PREPARE, (void *)(long)cpu);
- check_cpu_stall_init();
}
#include "rcutree_plugin.h"
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 4b69291b093..c896b5045d9 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -102,10 +102,6 @@ struct rcu_dynticks {
/* idle-period nonlazy_posted snapshot. */
int tick_nohz_enabled_snap; /* Previously seen value from sysfs. */
#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
-#ifdef CONFIG_RCU_USER_QS
- bool ignore_user_qs; /* Treat userspace as extended QS or not */
- bool in_user; /* Is the CPU in userland from RCU POV? */
-#endif
};
/* RCU's kthread states for tracing. */
@@ -282,6 +278,8 @@ struct rcu_data {
*/
struct rcu_head *nxtlist;
struct rcu_head **nxttail[RCU_NEXT_SIZE];
+ unsigned long nxtcompleted[RCU_NEXT_SIZE];
+ /* grace periods for sublists. */
long qlen_lazy; /* # of lazy queued callbacks */
long qlen; /* # of queued callbacks, incl lazy */
long qlen_last_fqs_check;
@@ -343,11 +341,6 @@ struct rcu_data {
#define RCU_JIFFIES_TILL_FORCE_QS 3 /* for rsp->jiffies_force_qs */
-#ifdef CONFIG_PROVE_RCU
-#define RCU_STALL_DELAY_DELTA (5 * HZ)
-#else
-#define RCU_STALL_DELAY_DELTA 0
-#endif
#define RCU_STALL_RAT_DELAY 2 /* Allow other CPUs time */
/* to take at least one */
/* scheduling clock irq */
diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index f6e5ec2932b..c1cc7e17ff9 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -40,8 +40,7 @@
#ifdef CONFIG_RCU_NOCB_CPU
static cpumask_var_t rcu_nocb_mask; /* CPUs to have callbacks offloaded. */
static bool have_rcu_nocb_mask; /* Was rcu_nocb_mask allocated? */
-static bool rcu_nocb_poll; /* Offload kthread are to poll. */
-module_param(rcu_nocb_poll, bool, 0444);
+static bool __read_mostly rcu_nocb_poll; /* Offload kthread are to poll. */
static char __initdata nocb_buf[NR_CPUS * 5];
#endif /* #ifdef CONFIG_RCU_NOCB_CPU */
@@ -2159,6 +2158,13 @@ static int __init rcu_nocb_setup(char *str)
}
__setup("rcu_nocbs=", rcu_nocb_setup);
+static int __init parse_rcu_nocb_poll(char *arg)
+{
+ rcu_nocb_poll = 1;
+ return 0;
+}
+early_param("rcu_nocb_poll", parse_rcu_nocb_poll);
+
/* Is the specified CPU a no-CPUs CPU? */
static bool is_nocb_cpu(int cpu)
{
@@ -2366,10 +2372,11 @@ static int rcu_nocb_kthread(void *arg)
for (;;) {
/* If not polling, wait for next batch of callbacks. */
if (!rcu_nocb_poll)
- wait_event(rdp->nocb_wq, rdp->nocb_head);
+ wait_event_interruptible(rdp->nocb_wq, rdp->nocb_head);
list = ACCESS_ONCE(rdp->nocb_head);
if (!list) {
schedule_timeout_interruptible(1);
+ flush_signals(current);
continue;
}
diff --git a/kernel/trace/trace_clock.c b/kernel/trace/trace_clock.c
index 394783531cb..1bbb1b200ce 100644
--- a/kernel/trace/trace_clock.c
+++ b/kernel/trace/trace_clock.c
@@ -44,6 +44,7 @@ u64 notrace trace_clock_local(void)
return clock;
}
+EXPORT_SYMBOL_GPL(trace_clock_local);
/*
* trace_clock(): 'between' trace clock. Not completely serialized,