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-rw-r--r--kernel/rcu/Makefile1
-rw-r--r--kernel/rcu/rcuperf.c655
-rw-r--r--kernel/rcu/rcutorture.c12
-rw-r--r--kernel/rcu/tree.c231
-rw-r--r--kernel/rcu/tree.h18
-rw-r--r--kernel/rcu/tree_plugin.h37
-rw-r--r--kernel/rcu/tree_trace.c13
7 files changed, 848 insertions, 119 deletions
diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile
index 032b2c015beb..18dfc485225c 100644
--- a/kernel/rcu/Makefile
+++ b/kernel/rcu/Makefile
@@ -5,6 +5,7 @@ KCOV_INSTRUMENT := n
obj-y += update.o sync.o
obj-$(CONFIG_SRCU) += srcu.o
obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
+obj-$(CONFIG_RCU_PERF_TEST) += rcuperf.o
obj-$(CONFIG_TREE_RCU) += tree.o
obj-$(CONFIG_PREEMPT_RCU) += tree.o
obj-$(CONFIG_TREE_RCU_TRACE) += tree_trace.o
diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c
new file mode 100644
index 000000000000..3cee0d8393ed
--- /dev/null
+++ b/kernel/rcu/rcuperf.c
@@ -0,0 +1,655 @@
+/*
+ * Read-Copy Update module-based performance-test facility
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, you can access it online at
+ * http://www.gnu.org/licenses/gpl-2.0.html.
+ *
+ * Copyright (C) IBM Corporation, 2015
+ *
+ * Authors: Paul E. McKenney <paulmck@us.ibm.com>
+ */
+#include <linux/types.h>
+#include <linux/kernel.h>
+#include <linux/init.h>
+#include <linux/module.h>
+#include <linux/kthread.h>
+#include <linux/err.h>
+#include <linux/spinlock.h>
+#include <linux/smp.h>
+#include <linux/rcupdate.h>
+#include <linux/interrupt.h>
+#include <linux/sched.h>
+#include <linux/atomic.h>
+#include <linux/bitops.h>
+#include <linux/completion.h>
+#include <linux/moduleparam.h>
+#include <linux/percpu.h>
+#include <linux/notifier.h>
+#include <linux/reboot.h>
+#include <linux/freezer.h>
+#include <linux/cpu.h>
+#include <linux/delay.h>
+#include <linux/stat.h>
+#include <linux/srcu.h>
+#include <linux/slab.h>
+#include <asm/byteorder.h>
+#include <linux/torture.h>
+#include <linux/vmalloc.h>
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.vnet.ibm.com>");
+
+#define PERF_FLAG "-perf:"
+#define PERFOUT_STRING(s) \
+ pr_alert("%s" PERF_FLAG s "\n", perf_type)
+#define VERBOSE_PERFOUT_STRING(s) \
+ do { if (verbose) pr_alert("%s" PERF_FLAG " %s\n", perf_type, s); } while (0)
+#define VERBOSE_PERFOUT_ERRSTRING(s) \
+ do { if (verbose) pr_alert("%s" PERF_FLAG "!!! %s\n", perf_type, s); } while (0)
+
+torture_param(bool, gp_exp, true, "Use expedited GP wait primitives");
+torture_param(int, holdoff, 10, "Holdoff time before test start (s)");
+torture_param(int, nreaders, -1, "Number of RCU reader threads");
+torture_param(int, nwriters, -1, "Number of RCU updater threads");
+torture_param(bool, shutdown, false, "Shutdown at end of performance tests.");
+torture_param(bool, verbose, true, "Enable verbose debugging printk()s");
+
+static char *perf_type = "rcu";
+module_param(perf_type, charp, 0444);
+MODULE_PARM_DESC(perf_type, "Type of RCU to performance-test (rcu, rcu_bh, ...)");
+
+static int nrealreaders;
+static int nrealwriters;
+static struct task_struct **writer_tasks;
+static struct task_struct **reader_tasks;
+static struct task_struct *shutdown_task;
+
+static u64 **writer_durations;
+static int *writer_n_durations;
+static atomic_t n_rcu_perf_reader_started;
+static atomic_t n_rcu_perf_writer_started;
+static atomic_t n_rcu_perf_writer_finished;
+static wait_queue_head_t shutdown_wq;
+static u64 t_rcu_perf_writer_started;
+static u64 t_rcu_perf_writer_finished;
+static unsigned long b_rcu_perf_writer_started;
+static unsigned long b_rcu_perf_writer_finished;
+
+static int rcu_perf_writer_state;
+#define RTWS_INIT 0
+#define RTWS_EXP_SYNC 1
+#define RTWS_SYNC 2
+#define RTWS_IDLE 2
+#define RTWS_STOPPING 3
+
+#define MAX_MEAS 10000
+#define MIN_MEAS 100
+
+#if defined(MODULE) || defined(CONFIG_RCU_PERF_TEST_RUNNABLE)
+#define RCUPERF_RUNNABLE_INIT 1
+#else
+#define RCUPERF_RUNNABLE_INIT 0
+#endif
+static int perf_runnable = RCUPERF_RUNNABLE_INIT;
+module_param(perf_runnable, int, 0444);
+MODULE_PARM_DESC(perf_runnable, "Start rcuperf at boot");
+
+/*
+ * Operations vector for selecting different types of tests.
+ */
+
+struct rcu_perf_ops {
+ int ptype;
+ void (*init)(void);
+ void (*cleanup)(void);
+ int (*readlock)(void);
+ void (*readunlock)(int idx);
+ unsigned long (*started)(void);
+ unsigned long (*completed)(void);
+ unsigned long (*exp_completed)(void);
+ void (*sync)(void);
+ void (*exp_sync)(void);
+ const char *name;
+};
+
+static struct rcu_perf_ops *cur_ops;
+
+/*
+ * Definitions for rcu perf testing.
+ */
+
+static int rcu_perf_read_lock(void) __acquires(RCU)
+{
+ rcu_read_lock();
+ return 0;
+}
+
+static void rcu_perf_read_unlock(int idx) __releases(RCU)
+{
+ rcu_read_unlock();
+}
+
+static unsigned long __maybe_unused rcu_no_completed(void)
+{
+ return 0;
+}
+
+static void rcu_sync_perf_init(void)
+{
+}
+
+static struct rcu_perf_ops rcu_ops = {
+ .ptype = RCU_FLAVOR,
+ .init = rcu_sync_perf_init,
+ .readlock = rcu_perf_read_lock,
+ .readunlock = rcu_perf_read_unlock,
+ .started = rcu_batches_started,
+ .completed = rcu_batches_completed,
+ .exp_completed = rcu_exp_batches_completed,
+ .sync = synchronize_rcu,
+ .exp_sync = synchronize_rcu_expedited,
+ .name = "rcu"
+};
+
+/*
+ * Definitions for rcu_bh perf testing.
+ */
+
+static int rcu_bh_perf_read_lock(void) __acquires(RCU_BH)
+{
+ rcu_read_lock_bh();
+ return 0;
+}
+
+static void rcu_bh_perf_read_unlock(int idx) __releases(RCU_BH)
+{
+ rcu_read_unlock_bh();
+}
+
+static struct rcu_perf_ops rcu_bh_ops = {
+ .ptype = RCU_BH_FLAVOR,
+ .init = rcu_sync_perf_init,
+ .readlock = rcu_bh_perf_read_lock,
+ .readunlock = rcu_bh_perf_read_unlock,
+ .started = rcu_batches_started_bh,
+ .completed = rcu_batches_completed_bh,
+ .exp_completed = rcu_exp_batches_completed_sched,
+ .sync = synchronize_rcu_bh,
+ .exp_sync = synchronize_rcu_bh_expedited,
+ .name = "rcu_bh"
+};
+
+/*
+ * Definitions for srcu perf testing.
+ */
+
+DEFINE_STATIC_SRCU(srcu_ctl_perf);
+static struct srcu_struct *srcu_ctlp = &srcu_ctl_perf;
+
+static int srcu_perf_read_lock(void) __acquires(srcu_ctlp)
+{
+ return srcu_read_lock(srcu_ctlp);
+}
+
+static void srcu_perf_read_unlock(int idx) __releases(srcu_ctlp)
+{
+ srcu_read_unlock(srcu_ctlp, idx);
+}
+
+static unsigned long srcu_perf_completed(void)
+{
+ return srcu_batches_completed(srcu_ctlp);
+}
+
+static void srcu_perf_synchronize(void)
+{
+ synchronize_srcu(srcu_ctlp);
+}
+
+static void srcu_perf_synchronize_expedited(void)
+{
+ synchronize_srcu_expedited(srcu_ctlp);
+}
+
+static struct rcu_perf_ops srcu_ops = {
+ .ptype = SRCU_FLAVOR,
+ .init = rcu_sync_perf_init,
+ .readlock = srcu_perf_read_lock,
+ .readunlock = srcu_perf_read_unlock,
+ .started = NULL,
+ .completed = srcu_perf_completed,
+ .exp_completed = srcu_perf_completed,
+ .sync = srcu_perf_synchronize,
+ .exp_sync = srcu_perf_synchronize_expedited,
+ .name = "srcu"
+};
+
+/*
+ * Definitions for sched perf testing.
+ */
+
+static int sched_perf_read_lock(void)
+{
+ preempt_disable();
+ return 0;
+}
+
+static void sched_perf_read_unlock(int idx)
+{
+ preempt_enable();
+}
+
+static struct rcu_perf_ops sched_ops = {
+ .ptype = RCU_SCHED_FLAVOR,
+ .init = rcu_sync_perf_init,
+ .readlock = sched_perf_read_lock,
+ .readunlock = sched_perf_read_unlock,
+ .started = rcu_batches_started_sched,
+ .completed = rcu_batches_completed_sched,
+ .exp_completed = rcu_exp_batches_completed_sched,
+ .sync = synchronize_sched,
+ .exp_sync = synchronize_sched_expedited,
+ .name = "sched"
+};
+
+#ifdef CONFIG_TASKS_RCU
+
+/*
+ * Definitions for RCU-tasks perf testing.
+ */
+
+static int tasks_perf_read_lock(void)
+{
+ return 0;
+}
+
+static void tasks_perf_read_unlock(int idx)
+{
+}
+
+static struct rcu_perf_ops tasks_ops = {
+ .ptype = RCU_TASKS_FLAVOR,
+ .init = rcu_sync_perf_init,
+ .readlock = tasks_perf_read_lock,
+ .readunlock = tasks_perf_read_unlock,
+ .started = rcu_no_completed,
+ .completed = rcu_no_completed,
+ .sync = synchronize_rcu_tasks,
+ .exp_sync = synchronize_rcu_tasks,
+ .name = "tasks"
+};
+
+#define RCUPERF_TASKS_OPS &tasks_ops,
+
+static bool __maybe_unused torturing_tasks(void)
+{
+ return cur_ops == &tasks_ops;
+}
+
+#else /* #ifdef CONFIG_TASKS_RCU */
+
+#define RCUPERF_TASKS_OPS
+
+static bool __maybe_unused torturing_tasks(void)
+{
+ return false;
+}
+
+#endif /* #else #ifdef CONFIG_TASKS_RCU */
+
+/*
+ * If performance tests complete, wait for shutdown to commence.
+ */
+static void rcu_perf_wait_shutdown(void)
+{
+ cond_resched_rcu_qs();
+ if (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters)
+ return;
+ while (!torture_must_stop())
+ schedule_timeout_uninterruptible(1);
+}
+
+/*
+ * RCU perf reader kthread. Repeatedly does empty RCU read-side
+ * critical section, minimizing update-side interference.
+ */
+static int
+rcu_perf_reader(void *arg)
+{
+ unsigned long flags;
+ int idx;
+ long me = (long)arg;
+
+ VERBOSE_PERFOUT_STRING("rcu_perf_reader task started");
+ set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
+ set_user_nice(current, MAX_NICE);
+ atomic_inc(&n_rcu_perf_reader_started);
+
+ do {
+ local_irq_save(flags);
+ idx = cur_ops->readlock();
+ cur_ops->readunlock(idx);
+ local_irq_restore(flags);
+ rcu_perf_wait_shutdown();
+ } while (!torture_must_stop());
+ torture_kthread_stopping("rcu_perf_reader");
+ return 0;
+}
+
+/*
+ * RCU perf writer kthread. Repeatedly does a grace period.
+ */
+static int
+rcu_perf_writer(void *arg)
+{
+ int i = 0;
+ int i_max;
+ long me = (long)arg;
+ struct sched_param sp;
+ bool started = false, done = false, alldone = false;
+ u64 t;
+ u64 *wdp;
+ u64 *wdpp = writer_durations[me];
+
+ VERBOSE_PERFOUT_STRING("rcu_perf_writer task started");
+ WARN_ON(rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp);
+ WARN_ON(rcu_gp_is_normal() && gp_exp);
+ WARN_ON(!wdpp);
+ set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids));
+ sp.sched_priority = 1;
+ sched_setscheduler_nocheck(current, SCHED_FIFO, &sp);
+
+ if (holdoff)
+ schedule_timeout_uninterruptible(holdoff * HZ);
+
+ t = ktime_get_mono_fast_ns();
+ if (atomic_inc_return(&n_rcu_perf_writer_started) >= nrealwriters) {
+ t_rcu_perf_writer_started = t;
+ if (gp_exp) {
+ b_rcu_perf_writer_started =
+ cur_ops->exp_completed() / 2;
+ } else {
+ b_rcu_perf_writer_started =
+ cur_ops->completed();
+ }
+ }
+
+ do {
+ wdp = &wdpp[i];
+ *wdp = ktime_get_mono_fast_ns();
+ if (gp_exp) {
+ rcu_perf_writer_state = RTWS_EXP_SYNC;
+ cur_ops->exp_sync();
+ } else {
+ rcu_perf_writer_state = RTWS_SYNC;
+ cur_ops->sync();
+ }
+ rcu_perf_writer_state = RTWS_IDLE;
+ t = ktime_get_mono_fast_ns();
+ *wdp = t - *wdp;
+ i_max = i;
+ if (!started &&
+ atomic_read(&n_rcu_perf_writer_started) >= nrealwriters)
+ started = true;
+ if (!done && i >= MIN_MEAS) {
+ done = true;
+ sp.sched_priority = 0;
+ sched_setscheduler_nocheck(current,
+ SCHED_NORMAL, &sp);
+ pr_alert("%s" PERF_FLAG
+ "rcu_perf_writer %ld has %d measurements\n",
+ perf_type, me, MIN_MEAS);
+ if (atomic_inc_return(&n_rcu_perf_writer_finished) >=
+ nrealwriters) {
+ schedule_timeout_interruptible(10);
+ rcu_ftrace_dump(DUMP_ALL);
+ PERFOUT_STRING("Test complete");
+ t_rcu_perf_writer_finished = t;
+ if (gp_exp) {
+ b_rcu_perf_writer_finished =
+ cur_ops->exp_completed() / 2;
+ } else {
+ b_rcu_perf_writer_finished =
+ cur_ops->completed();
+ }
+ if (shutdown) {
+ smp_mb(); /* Assign before wake. */
+ wake_up(&shutdown_wq);
+ }
+ }
+ }
+ if (done && !alldone &&
+ atomic_read(&n_rcu_perf_writer_finished) >= nrealwriters)
+ alldone = true;
+ if (started && !alldone && i < MAX_MEAS - 1)
+ i++;
+ rcu_perf_wait_shutdown();
+ } while (!torture_must_stop());
+ rcu_perf_writer_state = RTWS_STOPPING;
+ writer_n_durations[me] = i_max;
+ torture_kthread_stopping("rcu_perf_writer");
+ return 0;
+}
+
+static inline void
+rcu_perf_print_module_parms(struct rcu_perf_ops *cur_ops, const char *tag)
+{
+ pr_alert("%s" PERF_FLAG
+ "--- %s: nreaders=%d nwriters=%d verbose=%d shutdown=%d\n",
+ perf_type, tag, nrealreaders, nrealwriters, verbose, shutdown);
+}
+
+static void
+rcu_perf_cleanup(void)
+{
+ int i;
+ int j;
+ int ngps = 0;
+ u64 *wdp;
+ u64 *wdpp;
+
+ if (torture_cleanup_begin())
+ return;
+
+ if (reader_tasks) {
+ for (i = 0; i < nrealreaders; i++)
+ torture_stop_kthread(rcu_perf_reader,
+ reader_tasks[i]);
+ kfree(reader_tasks);
+ }
+
+ if (writer_tasks) {
+ for (i = 0; i < nrealwriters; i++) {
+ torture_stop_kthread(rcu_perf_writer,
+ writer_tasks[i]);
+ if (!writer_n_durations)
+ continue;
+ j = writer_n_durations[i];
+ pr_alert("%s%s writer %d gps: %d\n",
+ perf_type, PERF_FLAG, i, j);
+ ngps += j;
+ }
+ pr_alert("%s%s start: %llu end: %llu duration: %llu gps: %d batches: %ld\n",
+ perf_type, PERF_FLAG,
+ t_rcu_perf_writer_started, t_rcu_perf_writer_finished,
+ t_rcu_perf_writer_finished -
+ t_rcu_perf_writer_started,
+ ngps,
+ b_rcu_perf_writer_finished -
+ b_rcu_perf_writer_started);
+ for (i = 0; i < nrealwriters; i++) {
+ if (!writer_durations)
+ break;
+ if (!writer_n_durations)
+ continue;
+ wdpp = writer_durations[i];
+ if (!wdpp)
+ continue;
+ for (j = 0; j <= writer_n_durations[i]; j++) {
+ wdp = &wdpp[j];
+ pr_alert("%s%s %4d writer-duration: %5d %llu\n",
+ perf_type, PERF_FLAG,
+ i, j, *wdp);
+ if (j % 100 == 0)
+ schedule_timeout_uninterruptible(1);
+ }
+ kfree(writer_durations[i]);
+ }
+ kfree(writer_tasks);
+ kfree(writer_durations);
+ kfree(writer_n_durations);
+ }
+
+ /* Do flavor-specific cleanup operations. */
+ if (cur_ops->cleanup != NULL)
+ cur_ops->cleanup();
+
+ torture_cleanup_end();
+}
+
+/*
+ * Return the number if non-negative. If -1, the number of CPUs.
+ * If less than -1, that much less than the number of CPUs, but
+ * at least one.
+ */
+static int compute_real(int n)
+{
+ int nr;
+
+ if (n >= 0) {
+ nr = n;
+ } else {
+ nr = num_online_cpus() + 1 + n;
+ if (nr <= 0)
+ nr = 1;
+ }
+ return nr;
+}
+
+/*
+ * RCU perf shutdown kthread. Just waits to be awakened, then shuts
+ * down system.
+ */
+static int
+rcu_perf_shutdown(void *arg)
+{
+ do {
+ wait_event(shutdown_wq,
+ atomic_read(&n_rcu_perf_writer_finished) >=
+ nrealwriters);
+ } while (atomic_read(&n_rcu_perf_writer_finished) < nrealwriters);
+ smp_mb(); /* Wake before output. */
+ rcu_perf_cleanup();
+ kernel_power_off();
+ return -EINVAL;
+}
+
+static int __init
+rcu_perf_init(void)
+{
+ long i;
+ int firsterr = 0;
+ static struct rcu_perf_ops *perf_ops[] = {
+ &rcu_ops, &rcu_bh_ops, &srcu_ops, &sched_ops,
+ RCUPERF_TASKS_OPS
+ };
+
+ if (!torture_init_begin(perf_type, verbose, &perf_runnable))
+ return -EBUSY;
+
+ /* Process args and tell the world that the perf'er is on the job. */
+ for (i = 0; i < ARRAY_SIZE(perf_ops); i++) {
+ cur_ops = perf_ops[i];
+ if (strcmp(perf_type, cur_ops->name) == 0)
+ break;
+ }
+ if (i == ARRAY_SIZE(perf_ops)) {
+ pr_alert("rcu-perf: invalid perf type: \"%s\"\n",
+ perf_type);
+ pr_alert("rcu-perf types:");
+ for (i = 0; i < ARRAY_SIZE(perf_ops); i++)
+ pr_alert(" %s", perf_ops[i]->name);
+ pr_alert("\n");
+ firsterr = -EINVAL;
+ goto unwind;
+ }
+ if (cur_ops->init)
+ cur_ops->init();
+
+ nrealwriters = compute_real(nwriters);
+ nrealreaders = compute_real(nreaders);
+ atomic_set(&n_rcu_perf_reader_started, 0);
+ atomic_set(&n_rcu_perf_writer_started, 0);
+ atomic_set(&n_rcu_perf_writer_finished, 0);
+ rcu_perf_print_module_parms(cur_ops, "Start of test");
+
+ /* Start up the kthreads. */
+
+ if (shutdown) {
+ init_waitqueue_head(&shutdown_wq);
+ firsterr = torture_create_kthread(rcu_perf_shutdown, NULL,
+ shutdown_task);
+ if (firsterr)
+ goto unwind;
+ schedule_timeout_uninterruptible(1);
+ }
+ reader_tasks = kcalloc(nrealreaders, sizeof(reader_tasks[0]),
+ GFP_KERNEL);
+ if (reader_tasks == NULL) {
+ VERBOSE_PERFOUT_ERRSTRING("out of memory");
+ firsterr = -ENOMEM;
+ goto unwind;
+ }
+ for (i = 0; i < nrealreaders; i++) {
+ firsterr = torture_create_kthread(rcu_perf_reader, (void *)i,
+ reader_tasks[i]);
+ if (firsterr)
+ goto unwind;
+ }
+ while (atomic_read(&n_rcu_perf_reader_started) < nrealreaders)
+ schedule_timeout_uninterruptible(1);
+ writer_tasks = kcalloc(nrealwriters, sizeof(reader_tasks[0]),
+ GFP_KERNEL);
+ writer_durations = kcalloc(nrealwriters, sizeof(*writer_durations),
+ GFP_KERNEL);
+ writer_n_durations =
+ kcalloc(nrealwriters, sizeof(*writer_n_durations),
+ GFP_KERNEL);
+ if (!writer_tasks || !writer_durations || !writer_n_durations) {
+ VERBOSE_PERFOUT_ERRSTRING("out of memory");
+ firsterr = -ENOMEM;
+ goto unwind;
+ }
+ for (i = 0; i < nrealwriters; i++) {
+ writer_durations[i] =
+ kcalloc(MAX_MEAS, sizeof(*writer_durations[i]),
+ GFP_KERNEL);
+ if (!writer_durations[i])
+ goto unwind;
+ firsterr = torture_create_kthread(rcu_perf_writer, (void *)i,
+ writer_tasks[i]);
+ if (firsterr)
+ goto unwind;
+ }
+ torture_init_end();
+ return 0;
+
+unwind:
+ torture_init_end();
+ rcu_perf_cleanup();
+ return firsterr;
+}
+
+module_init(rcu_perf_init);
+module_exit(rcu_perf_cleanup);
diff --git a/kernel/rcu/rcutorture.c b/kernel/rcu/rcutorture.c
index 463867c43221..084a28a732eb 100644
--- a/kernel/rcu/rcutorture.c
+++ b/kernel/rcu/rcutorture.c
@@ -130,8 +130,8 @@ static struct rcu_torture __rcu *rcu_torture_current;
static unsigned long rcu_torture_current_version;
static struct rcu_torture rcu_tortures[10 * RCU_TORTURE_PIPE_LEN];
static DEFINE_SPINLOCK(rcu_torture_lock);
-static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count) = { 0 };
-static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch) = { 0 };
+static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_count);
+static DEFINE_PER_CPU(long [RCU_TORTURE_PIPE_LEN + 1], rcu_torture_batch);
static atomic_t rcu_torture_wcount[RCU_TORTURE_PIPE_LEN + 1];
static atomic_t n_rcu_torture_alloc;
static atomic_t n_rcu_torture_alloc_fail;
@@ -916,7 +916,7 @@ rcu_torture_fqs(void *arg)
static int
rcu_torture_writer(void *arg)
{
- bool can_expedite = !rcu_gp_is_expedited();
+ bool can_expedite = !rcu_gp_is_expedited() && !rcu_gp_is_normal();
int expediting = 0;
unsigned long gp_snap;
bool gp_cond1 = gp_cond, gp_exp1 = gp_exp, gp_normal1 = gp_normal;
@@ -932,7 +932,7 @@ rcu_torture_writer(void *arg)
VERBOSE_TOROUT_STRING("rcu_torture_writer task started");
if (!can_expedite) {
pr_alert("%s" TORTURE_FLAG
- " Grace periods expedited from boot/sysfs for %s,\n",
+ " GP expediting controlled from boot/sysfs for %s,\n",
torture_type, cur_ops->name);
pr_alert("%s" TORTURE_FLAG
" Disabled dynamic grace-period expediting.\n",
@@ -1478,7 +1478,9 @@ static int rcu_torture_barrier_cbs(void *arg)
* The above smp_load_acquire() ensures barrier_phase load
* is ordered before the folloiwng ->call().
*/
+ local_irq_disable(); /* Just to test no-irq call_rcu(). */
cur_ops->call(&rcu, rcu_torture_barrier_cbf);
+ local_irq_enable();
if (atomic_dec_and_test(&barrier_cbs_count))
wake_up(&barrier_wq);
} while (!torture_must_stop());
@@ -1585,7 +1587,7 @@ static int rcutorture_cpu_notify(struct notifier_block *self,
{
long cpu = (long)hcpu;
- switch (action) {
+ switch (action & ~CPU_TASKS_FROZEN) {
case CPU_ONLINE:
case CPU_DOWN_FAILED:
(void)rcutorture_booster_init(cpu);
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 86edb92276d3..c7f1bc4f817c 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -102,6 +102,8 @@ struct rcu_state sname##_state = { \
.barrier_mutex = __MUTEX_INITIALIZER(sname##_state.barrier_mutex), \
.name = RCU_STATE_NAME(sname), \
.abbr = sabbr, \
+ .exp_mutex = __MUTEX_INITIALIZER(sname##_state.exp_mutex), \
+ .exp_wake_mutex = __MUTEX_INITIALIZER(sname##_state.exp_wake_mutex), \
}
RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
@@ -370,6 +372,21 @@ void rcu_all_qs(void)
rcu_momentary_dyntick_idle();
local_irq_restore(flags);
}
+ if (unlikely(raw_cpu_read(rcu_sched_data.cpu_no_qs.b.exp))) {
+ /*
+ * Yes, we just checked a per-CPU variable with preemption
+ * enabled, so we might be migrated to some other CPU at
+ * this point. That is OK because in that case, the
+ * migration will supply the needed quiescent state.
+ * We might end up needlessly disabling preemption and
+ * invoking rcu_sched_qs() on the destination CPU, but
+ * the probability and cost are both quite low, so this
+ * should not be a problem in practice.
+ */
+ preempt_disable();
+ rcu_sched_qs();
+ preempt_enable();
+ }
this_cpu_inc(rcu_qs_ctr);
barrier(); /* Avoid RCU read-side critical sections leaking up. */
}
@@ -462,6 +479,28 @@ unsigned long rcu_batches_completed_bh(void)
EXPORT_SYMBOL_GPL(rcu_batches_completed_bh);
/*
+ * Return the number of RCU expedited batches completed thus far for
+ * debug & stats. Odd numbers mean that a batch is in progress, even
+ * numbers mean idle. The value returned will thus be roughly double
+ * the cumulative batches since boot.
+ */
+unsigned long rcu_exp_batches_completed(void)
+{
+ return rcu_state_p->expedited_sequence;
+}
+EXPORT_SYMBOL_GPL(rcu_exp_batches_completed);
+
+/*
+ * Return the number of RCU-sched expedited batches completed thus far
+ * for debug & stats. Similar to rcu_exp_batches_completed().
+ */
+unsigned long rcu_exp_batches_completed_sched(void)
+{
+ return rcu_sched_state.expedited_sequence;
+}
+EXPORT_SYMBOL_GPL(rcu_exp_batches_completed_sched);
+
+/*
* Force a quiescent state.
*/
void rcu_force_quiescent_state(void)
@@ -3421,8 +3460,12 @@ static void rcu_exp_gp_seq_end(struct rcu_state *rsp)
}
static unsigned long rcu_exp_gp_seq_snap(struct rcu_state *rsp)
{
+ unsigned long s;
+
smp_mb(); /* Caller's modifications seen first by other CPUs. */
- return rcu_seq_snap(&rsp->expedited_sequence);
+ s = rcu_seq_snap(&rsp->expedited_sequence);
+ trace_rcu_exp_grace_period(rsp->name, s, TPS("snap"));
+ return s;
}
static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s)
{
@@ -3514,7 +3557,7 @@ static void __maybe_unused sync_exp_reset_tree(struct rcu_state *rsp)
* for the current expedited grace period. Works only for preemptible
* RCU -- other RCU implementation use other means.
*
- * Caller must hold the root rcu_node's exp_funnel_mutex.
+ * Caller must hold the rcu_state's exp_mutex.
*/
static int sync_rcu_preempt_exp_done(struct rcu_node *rnp)
{
@@ -3530,8 +3573,8 @@ static int sync_rcu_preempt_exp_done(struct rcu_node *rnp)
* recursively up the tree. (Calm down, calm down, we do the recursion
* iteratively!)
*
- * Caller must hold the root rcu_node's exp_funnel_mutex and the
- * specified rcu_node structure's ->lock.
+ * Caller must hold the rcu_state's exp_mutex and the specified rcu_node
+ * structure's ->lock.
*/
static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
bool wake, unsigned long flags)
@@ -3568,7 +3611,7 @@ static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
* Report expedited quiescent state for specified node. This is a
* lock-acquisition wrapper function for __rcu_report_exp_rnp().
*
- * Caller must hold the root rcu_node's exp_funnel_mutex.
+ * Caller must hold the rcu_state's exp_mutex.
*/
static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp,
struct rcu_node *rnp, bool wake)
@@ -3581,8 +3624,8 @@ static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp,
/*
* Report expedited quiescent state for multiple CPUs, all covered by the
- * specified leaf rcu_node structure. Caller must hold the root
- * rcu_node's exp_funnel_mutex.
+ * specified leaf rcu_node structure. Caller must hold the rcu_state's
+ * exp_mutex.
*/
static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp,
unsigned long mask, bool wake)
@@ -3600,7 +3643,6 @@ static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp,
/*
* Report expedited quiescent state for specified rcu_data (CPU).
- * Caller must hold the root rcu_node's exp_funnel_mutex.
*/
static void rcu_report_exp_rdp(struct rcu_state *rsp, struct rcu_data *rdp,
bool wake)
@@ -3609,15 +3651,11 @@ static void rcu_report_exp_rdp(struct rcu_state *rsp, struct rcu_data *rdp,
}
/* Common code for synchronize_{rcu,sched}_expedited() work-done checking. */
-static bool sync_exp_work_done(struct rcu_state *rsp, struct rcu_node *rnp,
- struct rcu_data *rdp,
- atomic_long_t *stat, unsigned long s)
+static bool sync_exp_work_done(struct rcu_state *rsp, atomic_long_t *stat,
+ unsigned long s)
{
if (rcu_exp_gp_seq_done(rsp, s)) {
- if (rnp)
- mutex_unlock(&rnp->exp_funnel_mutex);
- else if (rdp)
- mutex_unlock(&rdp->exp_funnel_mutex);
+ trace_rcu_exp_grace_period(rsp->name, s, TPS("done"));
/* Ensure test happens before caller kfree(). */
smp_mb__before_atomic(); /* ^^^ */
atomic_long_inc(stat);
@@ -3627,59 +3665,65 @@ static bool sync_exp_work_done(struct rcu_state *rsp, struct rcu_node *rnp,
}
/*
- * Funnel-lock acquisition for expedited grace periods. Returns a
- * pointer to the root rcu_node structure, or NULL if some other
- * task did the expedited grace period for us.
+ * Funnel-lock acquisition for expedited grace periods. Returns true
+ * if some other task completed an expedited grace period that this task
+ * can piggy-back on, and with no mutex held. Otherwise, returns false
+ * with the mutex held, indicating that the caller must actually do the
+ * expedited grace period.
*/
-static struct rcu_node *exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
+static bool exp_funnel_lock(struct rcu_state *rsp, unsigned long s)
{
struct rcu_data *rdp = per_cpu_ptr(rsp->rda, raw_smp_processor_id());
- struct rcu_node *rnp0;
- struct rcu_node *rnp1 = NULL;
+ struct rcu_node *rnp = rdp->mynode;
+ struct rcu_node *rnp_root = rcu_get_root(rsp);
+
+ /* Low-contention fastpath. */
+ if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s) &&
+ (rnp == rnp_root ||
+ ULONG_CMP_LT(READ_ONCE(rnp_root->exp_seq_rq), s)) &&
+ !mutex_is_locked(&rsp->exp_mutex) &&
+ mutex_trylock(&rsp->exp_mutex))
+ goto fastpath;
/*
- * First try directly acquiring the root lock in order to reduce
- * latency in the common case where expedited grace periods are
- * rare. We check mutex_is_locked() to avoid pathological levels of
- * memory contention on ->exp_funnel_mutex in the heavy-load case.
+ * Each pass through the following loop works its way up
+ * the rcu_node tree, returning if others have done the work or
+ * otherwise falls through to acquire rsp->exp_mutex. The mapping
+ * from CPU to rcu_node structure can be inexact, as it is just
+ * promoting locality and is not strictly needed for correctness.
*/
- rnp0 = rcu_get_root(rsp);
- if (!mutex_is_locked(&rnp0->exp_funnel_mutex)) {
- if (mutex_trylock(&rnp0->exp_funnel_mutex)) {
- if (sync_exp_work_done(rsp, rnp0, NULL,
- &rdp->expedited_workdone0, s))
- return NULL;
- return rnp0;
+ for (; rnp != NULL; rnp = rnp->parent) {
+ if (sync_exp_work_done(rsp, &rdp->exp_workdone1, s))
+ return true;
+
+ /* Work not done, either wait here or go up. */
+ spin_lock(&rnp->exp_lock);
+ if (ULONG_CMP_GE(rnp->exp_seq_rq, s)) {
+
+ /* Someone else doing GP, so wait for them. */
+ spin_unlock(&rnp->exp_lock);
+ trace_rcu_exp_funnel_lock(rsp->name, rnp->level,
+ rnp->grplo, rnp->grphi,
+ TPS("wait"));
+ wait_event(rnp->exp_wq[(s >> 1) & 0x3],
+ sync_exp_work_done(rsp,
+ &rdp->exp_workdone2, s));
+ return true;
}
+ rnp->exp_seq_rq = s; /* Followers can wait on us. */
+ spin_unlock(&rnp->exp_lock);
+ trace_rcu_exp_funnel_lock(rsp->name, rnp->level, rnp->grplo,
+ rnp->grphi, TPS("nxtlvl"));
}
-
- /*
- * Each pass through the following loop works its way
- * up the rcu_node tree, returning if others have done the
- * work or otherwise falls through holding the root rnp's
- * ->exp_funnel_mutex. The mapping from CPU to rcu_node structure
- * can be inexact, as it is just promoting locality and is not
- * strictly needed for correctness.
- */
- if (sync_exp_work_done(rsp, NULL, NULL, &rdp->expedited_workdone1, s))
- return NULL;
- mutex_lock(&rdp->exp_funnel_mutex);
- rnp0 = rdp->mynode;
- for (; rnp0 != NULL; rnp0 = rnp0->parent) {
- if (sync_exp_work_done(rsp, rnp1, rdp,
- &rdp->expedited_workdone2, s))
- return NULL;
- mutex_lock(&rnp0->exp_funnel_mutex);
- if (rnp1)
- mutex_unlock(&rnp1->exp_funnel_mutex);
- else
- mutex_unlock(&rdp->exp_funnel_mutex);
- rnp1 = rnp0;
+ mutex_lock(&rsp->exp_mutex);
+fastpath:
+ if (sync_exp_work_done(rsp, &rdp->exp_workdone3, s)) {
+ mutex_unlock(&rsp->exp_mutex);
+ return true;
}
- if (sync_exp_work_done(rsp, rnp1, rdp,
- &rdp->expedited_workdone3, s))
- return NULL;
- return rnp1;
+ rcu_exp_gp_seq_start(rsp);
+ trace_rcu_exp_grace_period(rsp->name, s, TPS("start"));
+ return false;
}
/* Invoked on each online non-idle CPU for expedited quiescent state. */
@@ -3694,6 +3738,11 @@ static void sync_sched_exp_handler(void *data)
if (!(READ_ONCE(rnp->expmask) & rdp->grpmask) ||
__this_cpu_read(rcu_sched_data.cpu_no_qs.b.exp))
return;
+ if (rcu_is_cpu_rrupt_from_idle()) {
+ rcu_report_exp_rdp(&rcu_sched_state,
+ this_cpu_ptr(&rcu_sched_data), true);
+ return;
+ }
__this_cpu_write(rcu_sched_data.cpu_no_qs.b.exp, true);
resched_cpu(smp_processor_id());
}
@@ -3818,7 +3867,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
rsp->name);
ndetected = 0;
rcu_for_each_leaf_node(rsp, rnp) {
- ndetected = rcu_print_task_exp_stall(rnp);
+ ndetected += rcu_print_task_exp_stall(rnp);
mask = 1;
for (cpu = rnp->grplo; cpu <= rnp->grphi; cpu++, mask <<= 1) {
struct rcu_data *rdp;
@@ -3828,7 +3877,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
ndetected++;
rdp = per_cpu_ptr(rsp->rda, cpu);
pr_cont(" %d-%c%c%c", cpu,
- "O."[cpu_online(cpu)],
+ "O."[!!cpu_online(cpu)],
"o."[!!(rdp->grpmask & rnp->expmaskinit)],
"N."[!!(rdp->grpmask & rnp->expmaskinitnext)]);
}
@@ -3837,7 +3886,7 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
pr_cont(" } %lu jiffies s: %lu root: %#lx/%c\n",
jiffies - jiffies_start, rsp->expedited_sequence,
rnp_root->expmask, ".T"[!!rnp_root->exp_tasks]);
- if (!ndetected) {
+ if (ndetected) {
pr_err("blocking rcu_node structures:");
rcu_for_each_node_breadth_first(rsp, rnp) {
if (rnp == rnp_root)
@@ -3863,6 +3912,41 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
}
}
+/*
+ * Wait for the current expedited grace period to complete, and then
+ * wake up everyone who piggybacked on the just-completed expedited
+ * grace period. Also update all the ->exp_seq_rq counters as needed
+ * in order to avoid counter-wrap problems.
+ */
+static void rcu_exp_wait_wake(struct rcu_state *rsp, unsigned long s)
+{
+ struct rcu_node *rnp;
+
+ synchronize_sched_expedited_wait(rsp);
+ rcu_exp_gp_seq_end(rsp);
+ trace_rcu_exp_grace_period(rsp->name, s, TPS("end"));
+
+ /*
+ * Switch over to wakeup mode, allowing the next GP, but -only- the
+ * next GP, to proceed.
+ */
+ mutex_lock(&rsp->exp_wake_mutex);
+ mutex_unlock(&rsp->exp_mutex);
+
+ rcu_for_each_node_breadth_first(rsp, rnp) {
+ if (ULONG_CMP_LT(READ_ONCE(rnp->exp_seq_rq), s)) {
+ spin_lock(&rnp->exp_lock);
+ /* Recheck, avoid hang in case someone just arrived. */
+ if (ULONG_CMP_LT(rnp->exp_seq_rq, s))
+ rnp->exp_seq_rq = s;
+ spin_unlock(&rnp->exp_lock);
+ }
+ wake_up_all(&rnp->exp_wq[(rsp->expedited_sequence >> 1) & 0x3]);
+ }
+ trace_rcu_exp_grace_period(rsp->name, s, TPS("endwake"));
+ mutex_unlock(&rsp->exp_wake_mutex);
+}
+
/**
* synchronize_sched_expedited - Brute-force RCU-sched grace period
*
@@ -3882,7 +3966,6 @@ static void synchronize_sched_expedited_wait(struct rcu_state *rsp)
void synchronize_sched_expedited(void)
{
unsigned long s;
- struct rcu_node *rnp;
struct rcu_state *rsp = &rcu_sched_state;
/* If only one CPU, this is automatically a grace period. */
@@ -3897,17 +3980,14 @@ void synchronize_sched_expedited(void)
/* Take a snapshot of the sequence number. */
s = rcu_exp_gp_seq_snap(rsp);
-
- rnp = exp_funnel_lock(rsp, s);
- if (rnp == NULL)
+ if (exp_funnel_lock(rsp, s))
return; /* Someone else did our work for us. */
- rcu_exp_gp_seq_start(rsp);
+ /* Initialize the rcu_node tree in preparation for the wait. */
sync_rcu_exp_select_cpus(rsp, sync_sched_exp_handler);
- synchronize_sched_expedited_wait(rsp);
- rcu_exp_gp_seq_end(rsp);
- mutex_unlock(&rnp->exp_funnel_mutex);
+ /* Wait and clean up, including waking everyone. */
+ rcu_exp_wait_wake(rsp, s);
}
EXPORT_SYMBOL_GPL(synchronize_sched_expedited);
@@ -4207,7 +4287,6 @@ rcu_boot_init_percpu_data(int cpu, struct rcu_state *rsp)
WARN_ON_ONCE(atomic_read(&rdp->dynticks->dynticks) != 1);
rdp->cpu = cpu;
rdp->rsp = rsp;
- mutex_init(&rdp->exp_funnel_mutex);
rcu_boot_init_nocb_percpu_data(rdp);
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
}
@@ -4465,10 +4544,8 @@ static void __init rcu_init_one(struct rcu_state *rsp)
{
static const char * const buf[] = RCU_NODE_NAME_INIT;
static const char * const fqs[] = RCU_FQS_NAME_INIT;
- static const char * const exp[] = RCU_EXP_NAME_INIT;
static struct lock_class_key rcu_node_class[RCU_NUM_LVLS];
static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS];
- static struct lock_class_key rcu_exp_class[RCU_NUM_LVLS];
static u8 fl_mask = 0x1;
int levelcnt[RCU_NUM_LVLS]; /* # nodes in each level. */
@@ -4527,9 +4604,11 @@ static void __init rcu_init_one(struct rcu_state *rsp)
rnp->level = i;
INIT_LIST_HEAD(&rnp->blkd_tasks);
rcu_init_one_nocb(rnp);
- mutex_init(&rnp->exp_funnel_mutex);
- lockdep_set_class_and_name(&rnp->exp_funnel_mutex,
- &rcu_exp_class[i], exp[i]);
+ init_waitqueue_head(&rnp->exp_wq[0]);
+ init_waitqueue_head(&rnp->exp_wq[1]);
+ init_waitqueue_head(&rnp->exp_wq[2]);
+ init_waitqueue_head(&rnp->exp_wq[3]);
+ spin_lock_init(&rnp->exp_lock);
}
}
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 34d3973f7223..e3959f5e6ddf 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -70,7 +70,6 @@
# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0 }
# define RCU_NODE_NAME_INIT { "rcu_node_0" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0" }
-# define RCU_EXP_NAME_INIT { "rcu_node_exp_0" }
#elif NR_CPUS <= RCU_FANOUT_2
# define RCU_NUM_LVLS 2
# define NUM_RCU_LVL_0 1
@@ -79,7 +78,6 @@
# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1 }
# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1" }
-# define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1" }
#elif NR_CPUS <= RCU_FANOUT_3
# define RCU_NUM_LVLS 3
# define NUM_RCU_LVL_0 1
@@ -89,7 +87,6 @@
# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2 }
# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2" }
-# define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1", "rcu_node_exp_2" }
#elif NR_CPUS <= RCU_FANOUT_4
# define RCU_NUM_LVLS 4
# define NUM_RCU_LVL_0 1
@@ -100,7 +97,6 @@
# define NUM_RCU_LVL_INIT { NUM_RCU_LVL_0, NUM_RCU_LVL_1, NUM_RCU_LVL_2, NUM_RCU_LVL_3 }
# define RCU_NODE_NAME_INIT { "rcu_node_0", "rcu_node_1", "rcu_node_2", "rcu_node_3" }
# define RCU_FQS_NAME_INIT { "rcu_node_fqs_0", "rcu_node_fqs_1", "rcu_node_fqs_2", "rcu_node_fqs_3" }
-# define RCU_EXP_NAME_INIT { "rcu_node_exp_0", "rcu_node_exp_1", "rcu_node_exp_2", "rcu_node_exp_3" }
#else
# error "CONFIG_RCU_FANOUT insufficient for NR_CPUS"
#endif /* #if (NR_CPUS) <= RCU_FANOUT_1 */
@@ -252,7 +248,9 @@ struct rcu_node {
/* Counts of upcoming no-CB GP requests. */
raw_spinlock_t fqslock ____cacheline_internodealigned_in_smp;
- struct mutex exp_funnel_mutex ____cacheline_internodealigned_in_smp;
+ spinlock_t exp_lock ____cacheline_internodealigned_in_smp;
+ unsigned long exp_seq_rq;
+ wait_queue_head_t exp_wq[4];
} ____cacheline_internodealigned_in_smp;
/*
@@ -387,11 +385,9 @@ struct rcu_data {
#ifdef CONFIG_RCU_FAST_NO_HZ
struct rcu_head oom_head;
#endif /* #ifdef CONFIG_RCU_FAST_NO_HZ */
- struct mutex exp_funnel_mutex;
- atomic_long_t expedited_workdone0; /* # done by others #0. */
- atomic_long_t expedited_workdone1; /* # done by others #1. */
- atomic_long_t expedited_workdone2; /* # done by others #2. */
- atomic_long_t expedited_workdone3; /* # done by others #3. */
+ atomic_long_t exp_workdone1; /* # done by others #1. */
+ atomic_long_t exp_workdone2; /* # done by others #2. */
+ atomic_long_t exp_workdone3; /* # done by others #3. */
/* 7) Callback offloading. */
#ifdef CONFIG_RCU_NOCB_CPU
@@ -505,6 +501,8 @@ struct rcu_state {
/* _rcu_barrier(). */
/* End of fields guarded by barrier_mutex. */
+ struct mutex exp_mutex; /* Serialize expedited GP. */
+ struct mutex exp_wake_mutex; /* Serialize wakeup. */
unsigned long expedited_sequence; /* Take a ticket. */
atomic_long_t expedited_normal; /* # fallbacks to normal. */
atomic_t expedited_need_qs; /* # CPUs left to check in. */
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h
index efdf7b61ce12..ff1cd4e1188d 100644
--- a/kernel/rcu/tree_plugin.h
+++ b/kernel/rcu/tree_plugin.h
@@ -722,18 +722,22 @@ static void sync_rcu_exp_handler(void *info)
* synchronize_rcu_expedited - Brute-force RCU grace period
*
* Wait for an RCU-preempt grace period, but expedite it. The basic
- * idea is to invoke synchronize_sched_expedited() to push all the tasks to
- * the ->blkd_tasks lists and wait for this list to drain. 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_rcu_expedited() in a loop,
- * please restructure your code to batch your updates, and then Use a
- * single synchronize_rcu() instead.
+ * idea is to IPI all non-idle non-nohz online CPUs. The IPI handler
+ * checks whether the CPU is in an RCU-preempt critical section, and
+ * if so, it sets a flag that causes the outermost rcu_read_unlock()
+ * to report the quiescent state. On the other hand, if the CPU is
+ * not in an RCU read-side critical section, the IPI handler reports
+ * the quiescent state immediately.
+ *
+ * Although this is a greate improvement over previous expedited
+ * implementations, it is still unfriendly to real-time workloads, so is
+ * thus not recommended for any sort of common-case code. In fact, if
+ * you are using synchronize_rcu_expedited() in a loop, please restructure
+ * your code to batch your updates, and then Use a single synchronize_rcu()
+ * instead.
*/
void synchronize_rcu_expedited(void)
{
- struct rcu_node *rnp;
- struct rcu_node *rnp_unlock;
struct rcu_state *rsp = rcu_state_p;
unsigned long s;
@@ -744,23 +748,14 @@ void synchronize_rcu_expedited(void)
}
s = rcu_exp_gp_seq_snap(rsp);
-
- rnp_unlock = exp_funnel_lock(rsp, s);
- if (rnp_unlock == NULL)
+ if (exp_funnel_lock(rsp, s))
return; /* Someone else did our work for us. */
- rcu_exp_gp_seq_start(rsp);
-
/* Initialize the rcu_node tree in preparation for the wait. */
sync_rcu_exp_select_cpus(rsp, sync_rcu_exp_handler);
- /* Wait for snapshotted ->blkd_tasks lists to drain. */
- rnp = rcu_get_root(rsp);
- synchronize_sched_expedited_wait(rsp);
-
- /* Clean up and exit. */
- rcu_exp_gp_seq_end(rsp);
- mutex_unlock(&rnp_unlock->exp_funnel_mutex);
+ /* Wait for ->blkd_tasks lists to drain, then wake everyone up. */
+ rcu_exp_wait_wake(rsp, s);
}
EXPORT_SYMBOL_GPL(synchronize_rcu_expedited);
diff --git a/kernel/rcu/tree_trace.c b/kernel/rcu/tree_trace.c
index 1088e64f01ad..86782f9a4604 100644
--- a/kernel/rcu/tree_trace.c
+++ b/kernel/rcu/tree_trace.c
@@ -185,17 +185,16 @@ static int show_rcuexp(struct seq_file *m, void *v)
int cpu;
struct rcu_state *rsp = (struct rcu_state *)m->private;
struct rcu_data *rdp;
- unsigned long s0 = 0, s1 = 0, s2 = 0, s3 = 0;
+ unsigned long s1 = 0, s2 = 0, s3 = 0;
for_each_possible_cpu(cpu) {
rdp = per_cpu_ptr(rsp->rda, cpu);
- s0 += atomic_long_read(&rdp->expedited_workdone0);
- s1 += atomic_long_read(&rdp->expedited_workdone1);
- s2 += atomic_long_read(&rdp->expedited_workdone2);
- s3 += atomic_long_read(&rdp->expedited_workdone3);
+ s1 += atomic_long_read(&rdp->exp_workdone1);
+ s2 += atomic_long_read(&rdp->exp_workdone2);
+ s3 += atomic_long_read(&rdp->exp_workdone3);
}
- seq_printf(m, "s=%lu wd0=%lu wd1=%lu wd2=%lu wd3=%lu n=%lu enq=%d sc=%lu\n",
- rsp->expedited_sequence, s0, s1, s2, s3,
+ seq_printf(m, "s=%lu wd1=%lu wd2=%lu wd3=%lu n=%lu enq=%d sc=%lu\n",
+ rsp->expedited_sequence, s1, s2, s3,
atomic_long_read(&rsp->expedited_normal),
atomic_read(&rsp->expedited_need_qs),
rsp->expedited_sequence / 2);