doc.2015.10.06a: Documentation updates.
percpu-rwsem.2015.10.06a: Optimization of per-CPU reader-writer semaphores.
torture.2015.10.06a: Torture-test updates.
behavior, you might need to replace some of the cond_resched()
calls with calls to cond_resched_rcu_qs().
+o Booting Linux using a console connection that is too slow to
+ keep up with the boot-time console-message rate. For example,
+ a 115Kbaud serial console can be -way- too slow to keep up
+ with boot-time message rates, and will frequently result in
+ RCU CPU stall warning messages. Especially if you have added
+ debug printk()s.
+
o Anything that prevents RCU's grace-period kthreads from running.
This can result in the "All QSes seen" console-log message.
This message will include information on when the kthread last
torture_type The type of RCU to test, with string values as follows:
- "rcu": rcu_read_lock(), rcu_read_unlock() and call_rcu().
-
- "rcu_sync": rcu_read_lock(), rcu_read_unlock(), and
- synchronize_rcu().
-
- "rcu_expedited": rcu_read_lock(), rcu_read_unlock(), and
- synchronize_rcu_expedited().
+ "rcu": rcu_read_lock(), rcu_read_unlock() and call_rcu(),
+ along with expedited, synchronous, and polling
+ variants.
"rcu_bh": rcu_read_lock_bh(), rcu_read_unlock_bh(), and
- call_rcu_bh().
-
- "rcu_bh_sync": rcu_read_lock_bh(), rcu_read_unlock_bh(),
- and synchronize_rcu_bh().
+ call_rcu_bh(), along with expedited and synchronous
+ variants.
- "rcu_bh_expedited": rcu_read_lock_bh(), rcu_read_unlock_bh(),
- and synchronize_rcu_bh_expedited().
+ "rcu_busted": This tests an intentionally incorrect version
+ of RCU in order to help test rcutorture itself.
"srcu": srcu_read_lock(), srcu_read_unlock() and
- call_srcu().
-
- "srcu_sync": srcu_read_lock(), srcu_read_unlock() and
- synchronize_srcu().
-
- "srcu_expedited": srcu_read_lock(), srcu_read_unlock() and
- synchronize_srcu_expedited().
+ call_srcu(), along with expedited and
+ synchronous variants.
"sched": preempt_disable(), preempt_enable(), and
- call_rcu_sched().
-
- "sched_sync": preempt_disable(), preempt_enable(), and
- synchronize_sched().
+ call_rcu_sched(), along with expedited,
+ synchronous, and polling variants.
- "sched_expedited": preempt_disable(), preempt_enable(), and
- synchronize_sched_expedited().
+ "tasks": voluntary context switch and call_rcu_tasks(),
+ along with expedited and synchronous variants.
Defaults to "rcu".
};
DEFINE_SPINLOCK(foo_mutex);
- struct foo *gbl_foo;
+ struct foo __rcu *gbl_foo;
/*
* Create a new struct foo that is the same as the one currently
new_fp = kmalloc(sizeof(*new_fp), GFP_KERNEL);
spin_lock(&foo_mutex);
- old_fp = gbl_foo;
+ old_fp = rcu_dereference_protected(gbl_foo, lockdep_is_held(&foo_mutex));
*new_fp = *old_fp;
new_fp->a = new_a;
rcu_assign_pointer(gbl_foo, new_fp);
new_fp = kmalloc(sizeof(*new_fp), GFP_KERNEL);
spin_lock(&foo_mutex);
- old_fp = gbl_foo;
+ old_fp = rcu_dereference_protected(gbl_foo, lockdep_is_held(&foo_mutex));
*new_fp = *old_fp;
new_fp->a = new_a;
rcu_assign_pointer(gbl_foo, new_fp);
o "mutex_lock": mutex_lock() and mutex_unlock() pairs.
+ o "rtmutex_lock": rtmutex_lock() and rtmutex_unlock()
+ pairs. Kernel must have CONFIG_RT_MUTEX=y.
+
o "rwsem_lock": read/write down() and up() semaphore pairs.
torture_runnable Start locktorture at boot time in the case where the
operations" subsection for information on where to use these.
+ (*) lockless_dereference();
+ This can be thought of as a pointer-fetch wrapper around the
+ smp_read_barrier_depends() data-dependency barrier.
+
+ This is also similar to rcu_dereference(), but in cases where
+ object lifetime is handled by some mechanism other than RCU, for
+ example, when the objects removed only when the system goes down.
+ In addition, lockless_dereference() is used in some data structures
+ that can be used both with and without RCU.
+
+
(*) dma_wmb();
(*) dma_rmb();
(*) mutexes
(*) semaphores
(*) R/W semaphores
- (*) RCU
In all cases there are variants on "ACQUIRE" operations and "RELEASE" operations
for each construct. These operations all imply certain barriers:
#include <linux/rwsem.h>
#include <linux/percpu.h>
#include <linux/wait.h>
+#include <linux/rcu_sync.h>
#include <linux/lockdep.h>
struct percpu_rw_semaphore {
+ struct rcu_sync rss;
unsigned int __percpu *fast_read_ctr;
- atomic_t write_ctr;
struct rw_semaphore rw_sem;
atomic_t slow_read_ctr;
wait_queue_head_t write_waitq;
--- /dev/null
+/*
+ * RCU-based infrastructure for lightweight reader-writer locking
+ *
+ * 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) 2015, Red Hat, Inc.
+ *
+ * Author: Oleg Nesterov <oleg@redhat.com>
+ */
+
+#ifndef _LINUX_RCU_SYNC_H_
+#define _LINUX_RCU_SYNC_H_
+
+#include <linux/wait.h>
+#include <linux/rcupdate.h>
+
+enum rcu_sync_type { RCU_SYNC, RCU_SCHED_SYNC, RCU_BH_SYNC };
+
+/* Structure to mediate between updaters and fastpath-using readers. */
+struct rcu_sync {
+ int gp_state;
+ int gp_count;
+ wait_queue_head_t gp_wait;
+
+ int cb_state;
+ struct rcu_head cb_head;
+
+ enum rcu_sync_type gp_type;
+};
+
+extern void rcu_sync_lockdep_assert(struct rcu_sync *);
+
+/**
+ * rcu_sync_is_idle() - Are readers permitted to use their fastpaths?
+ * @rsp: Pointer to rcu_sync structure to use for synchronization
+ *
+ * Returns true if readers are permitted to use their fastpaths.
+ * Must be invoked within an RCU read-side critical section whose
+ * flavor matches that of the rcu_sync struture.
+ */
+static inline bool rcu_sync_is_idle(struct rcu_sync *rsp)
+{
+#ifdef CONFIG_PROVE_RCU
+ rcu_sync_lockdep_assert(rsp);
+#endif
+ return !rsp->gp_state; /* GP_IDLE */
+}
+
+extern void rcu_sync_init(struct rcu_sync *, enum rcu_sync_type);
+extern void rcu_sync_enter(struct rcu_sync *);
+extern void rcu_sync_exit(struct rcu_sync *);
+extern void rcu_sync_dtor(struct rcu_sync *);
+
+#define __RCU_SYNC_INITIALIZER(name, type) { \
+ .gp_state = 0, \
+ .gp_count = 0, \
+ .gp_wait = __WAIT_QUEUE_HEAD_INITIALIZER(name.gp_wait), \
+ .cb_state = 0, \
+ .gp_type = type, \
+ }
+
+#define __DEFINE_RCU_SYNC(name, type) \
+ struct rcu_sync_struct name = __RCU_SYNC_INITIALIZER(name, type)
+
+#define DEFINE_RCU_SYNC(name) \
+ __DEFINE_RCU_SYNC(name, RCU_SYNC)
+
+#define DEFINE_RCU_SCHED_SYNC(name) \
+ __DEFINE_RCU_SYNC(name, RCU_SCHED_SYNC)
+
+#define DEFINE_RCU_BH_SYNC(name) \
+ __DEFINE_RCU_SYNC(name, RCU_BH_SYNC)
+
+#endif /* _LINUX_RCU_SYNC_H_ */
*
* Copyright (C) IBM Corporation, 2014
*
- * Author: Paul E. McKenney <paulmck@us.ibm.com>
+ * Authors: Paul E. McKenney <paulmck@us.ibm.com>
+ * Davidlohr Bueso <dave@stgolabs.net>
* Based on kernel/rcu/torture.c.
*/
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/kthread.h>
+#include <linux/sched/rt.h>
#include <linux/spinlock.h>
#include <linux/rwlock.h>
#include <linux/mutex.h>
#include <linux/moduleparam.h>
#include <linux/delay.h>
#include <linux/slab.h>
+#include <linux/percpu-rwsem.h>
#include <linux/torture.h>
MODULE_LICENSE("GPL");
void (*init)(void);
int (*writelock)(void);
void (*write_delay)(struct torture_random_state *trsp);
+ void (*task_boost)(struct torture_random_state *trsp);
void (*writeunlock)(void);
int (*readlock)(void);
void (*read_delay)(struct torture_random_state *trsp);
void (*readunlock)(void);
- unsigned long flags;
+
+ unsigned long flags; /* for irq spinlocks */
const char *name;
};
/* BUGGY, do not use in real life!!! */
}
+static void torture_boost_dummy(struct torture_random_state *trsp)
+{
+ /* Only rtmutexes care about priority */
+}
+
static struct lock_torture_ops lock_busted_ops = {
.writelock = torture_lock_busted_write_lock,
.write_delay = torture_lock_busted_write_delay,
+ .task_boost = torture_boost_dummy,
.writeunlock = torture_lock_busted_write_unlock,
.readlock = NULL,
.read_delay = NULL,
static struct lock_torture_ops spin_lock_ops = {
.writelock = torture_spin_lock_write_lock,
.write_delay = torture_spin_lock_write_delay,
+ .task_boost = torture_boost_dummy,
.writeunlock = torture_spin_lock_write_unlock,
.readlock = NULL,
.read_delay = NULL,
static struct lock_torture_ops spin_lock_irq_ops = {
.writelock = torture_spin_lock_write_lock_irq,
.write_delay = torture_spin_lock_write_delay,
+ .task_boost = torture_boost_dummy,
.writeunlock = torture_lock_spin_write_unlock_irq,
.readlock = NULL,
.read_delay = NULL,
static struct lock_torture_ops rw_lock_ops = {
.writelock = torture_rwlock_write_lock,
.write_delay = torture_rwlock_write_delay,
+ .task_boost = torture_boost_dummy,
.writeunlock = torture_rwlock_write_unlock,
.readlock = torture_rwlock_read_lock,
.read_delay = torture_rwlock_read_delay,
static struct lock_torture_ops rw_lock_irq_ops = {
.writelock = torture_rwlock_write_lock_irq,
.write_delay = torture_rwlock_write_delay,
+ .task_boost = torture_boost_dummy,
.writeunlock = torture_rwlock_write_unlock_irq,
.readlock = torture_rwlock_read_lock_irq,
.read_delay = torture_rwlock_read_delay,
static struct lock_torture_ops mutex_lock_ops = {
.writelock = torture_mutex_lock,
.write_delay = torture_mutex_delay,
+ .task_boost = torture_boost_dummy,
.writeunlock = torture_mutex_unlock,
.readlock = NULL,
.read_delay = NULL,
.name = "mutex_lock"
};
+#ifdef CONFIG_RT_MUTEXES
+static DEFINE_RT_MUTEX(torture_rtmutex);
+
+static int torture_rtmutex_lock(void) __acquires(torture_rtmutex)
+{
+ rt_mutex_lock(&torture_rtmutex);
+ return 0;
+}
+
+static void torture_rtmutex_boost(struct torture_random_state *trsp)
+{
+ int policy;
+ struct sched_param param;
+ const unsigned int factor = 50000; /* yes, quite arbitrary */
+
+ if (!rt_task(current)) {
+ /*
+ * (1) Boost priority once every ~50k operations. When the
+ * task tries to take the lock, the rtmutex it will account
+ * for the new priority, and do any corresponding pi-dance.
+ */
+ if (!(torture_random(trsp) %
+ (cxt.nrealwriters_stress * factor))) {
+ policy = SCHED_FIFO;
+ param.sched_priority = MAX_RT_PRIO - 1;
+ } else /* common case, do nothing */
+ return;
+ } else {
+ /*
+ * The task will remain boosted for another ~500k operations,
+ * then restored back to its original prio, and so forth.
+ *
+ * When @trsp is nil, we want to force-reset the task for
+ * stopping the kthread.
+ */
+ if (!trsp || !(torture_random(trsp) %
+ (cxt.nrealwriters_stress * factor * 2))) {
+ policy = SCHED_NORMAL;
+ param.sched_priority = 0;
+ } else /* common case, do nothing */
+ return;
+ }
+
+ sched_setscheduler_nocheck(current, policy, ¶m);
+}
+
+static void torture_rtmutex_delay(struct torture_random_state *trsp)
+{
+ const unsigned long shortdelay_us = 2;
+ const unsigned long longdelay_ms = 100;
+
+ /*
+ * We want a short delay mostly to emulate likely code, and
+ * we want a long delay occasionally to force massive contention.
+ */
+ if (!(torture_random(trsp) %
+ (cxt.nrealwriters_stress * 2000 * longdelay_ms)))
+ mdelay(longdelay_ms);
+ if (!(torture_random(trsp) %
+ (cxt.nrealwriters_stress * 2 * shortdelay_us)))
+ udelay(shortdelay_us);
+#ifdef CONFIG_PREEMPT
+ if (!(torture_random(trsp) % (cxt.nrealwriters_stress * 20000)))
+ preempt_schedule(); /* Allow test to be preempted. */
+#endif
+}
+
+static void torture_rtmutex_unlock(void) __releases(torture_rtmutex)
+{
+ rt_mutex_unlock(&torture_rtmutex);
+}
+
+static struct lock_torture_ops rtmutex_lock_ops = {
+ .writelock = torture_rtmutex_lock,
+ .write_delay = torture_rtmutex_delay,
+ .task_boost = torture_rtmutex_boost,
+ .writeunlock = torture_rtmutex_unlock,
+ .readlock = NULL,
+ .read_delay = NULL,
+ .readunlock = NULL,
+ .name = "rtmutex_lock"
+};
+#endif
+
static DECLARE_RWSEM(torture_rwsem);
static int torture_rwsem_down_write(void) __acquires(torture_rwsem)
{
static struct lock_torture_ops rwsem_lock_ops = {
.writelock = torture_rwsem_down_write,
.write_delay = torture_rwsem_write_delay,
+ .task_boost = torture_boost_dummy,
.writeunlock = torture_rwsem_up_write,
.readlock = torture_rwsem_down_read,
.read_delay = torture_rwsem_read_delay,
.name = "rwsem_lock"
};
+#include <linux/percpu-rwsem.h>
+static struct percpu_rw_semaphore pcpu_rwsem;
+
+void torture_percpu_rwsem_init(void)
+{
+ BUG_ON(percpu_init_rwsem(&pcpu_rwsem));
+}
+
+static int torture_percpu_rwsem_down_write(void) __acquires(pcpu_rwsem)
+{
+ percpu_down_write(&pcpu_rwsem);
+ return 0;
+}
+
+static void torture_percpu_rwsem_up_write(void) __releases(pcpu_rwsem)
+{
+ percpu_up_write(&pcpu_rwsem);
+}
+
+static int torture_percpu_rwsem_down_read(void) __acquires(pcpu_rwsem)
+{
+ percpu_down_read(&pcpu_rwsem);
+ return 0;
+}
+
+static void torture_percpu_rwsem_up_read(void) __releases(pcpu_rwsem)
+{
+ percpu_up_read(&pcpu_rwsem);
+}
+
+static struct lock_torture_ops percpu_rwsem_lock_ops = {
+ .init = torture_percpu_rwsem_init,
+ .writelock = torture_percpu_rwsem_down_write,
+ .write_delay = torture_rwsem_write_delay,
+ .task_boost = torture_boost_dummy,
+ .writeunlock = torture_percpu_rwsem_up_write,
+ .readlock = torture_percpu_rwsem_down_read,
+ .read_delay = torture_rwsem_read_delay,
+ .readunlock = torture_percpu_rwsem_up_read,
+ .name = "percpu_rwsem_lock"
+};
+
/*
* Lock torture writer kthread. Repeatedly acquires and releases
* the lock, checking for duplicate acquisitions.
if ((torture_random(&rand) & 0xfffff) == 0)
schedule_timeout_uninterruptible(1);
+ cxt.cur_ops->task_boost(&rand);
cxt.cur_ops->writelock();
if (WARN_ON_ONCE(lock_is_write_held))
lwsp->n_lock_fail++;
stutter_wait("lock_torture_writer");
} while (!torture_must_stop());
+
+ cxt.cur_ops->task_boost(NULL); /* reset prio */
torture_kthread_stopping("lock_torture_writer");
return 0;
}
&spin_lock_ops, &spin_lock_irq_ops,
&rw_lock_ops, &rw_lock_irq_ops,
&mutex_lock_ops,
+#ifdef CONFIG_RT_MUTEXES
+ &rtmutex_lock_ops,
+#endif
&rwsem_lock_ops,
+ &percpu_rwsem_lock_ops,
};
if (!torture_init_begin(torture_type, verbose, &torture_runnable))
for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
pr_alert(" %s", torture_ops[i]->name);
pr_alert("\n");
- torture_init_end();
- return -EINVAL;
+ firsterr = -EINVAL;
+ goto unwind;
}
if (cxt.cur_ops->init)
- cxt.cur_ops->init(); /* no "goto unwind" prior to this point!!! */
+ cxt.cur_ops->init();
if (nwriters_stress >= 0)
cxt.nrealwriters_stress = nwriters_stress;
if (strncmp(torture_type, "mutex", 5) == 0)
cxt.debug_lock = true;
#endif
+#ifdef CONFIG_DEBUG_RT_MUTEXES
+ if (strncmp(torture_type, "rtmutex", 7) == 0)
+ cxt.debug_lock = true;
+#endif
#ifdef CONFIG_DEBUG_SPINLOCK
if ((strncmp(torture_type, "spin", 4) == 0) ||
(strncmp(torture_type, "rw_lock", 7) == 0))
/* ->rw_sem represents the whole percpu_rw_semaphore for lockdep */
__init_rwsem(&brw->rw_sem, name, rwsem_key);
- atomic_set(&brw->write_ctr, 0);
+ rcu_sync_init(&brw->rss, RCU_SCHED_SYNC);
atomic_set(&brw->slow_read_ctr, 0);
init_waitqueue_head(&brw->write_waitq);
return 0;
}
+EXPORT_SYMBOL_GPL(__percpu_init_rwsem);
void percpu_free_rwsem(struct percpu_rw_semaphore *brw)
{
+ /*
+ * XXX: temporary kludge. The error path in alloc_super()
+ * assumes that percpu_free_rwsem() is safe after kzalloc().
+ */
+ if (!brw->fast_read_ctr)
+ return;
+
+ rcu_sync_dtor(&brw->rss);
free_percpu(brw->fast_read_ctr);
brw->fast_read_ctr = NULL; /* catch use after free bugs */
}
/*
- * This is the fast-path for down_read/up_read, it only needs to ensure
- * there is no pending writer (atomic_read(write_ctr) == 0) and inc/dec the
- * fast per-cpu counter. The writer uses synchronize_sched_expedited() to
- * serialize with the preempt-disabled section below.
- *
- * The nontrivial part is that we should guarantee acquire/release semantics
- * in case when
- *
- * R_W: down_write() comes after up_read(), the writer should see all
- * changes done by the reader
- * or
- * W_R: down_read() comes after up_write(), the reader should see all
- * changes done by the writer
+ * This is the fast-path for down_read/up_read. If it succeeds we rely
+ * on the barriers provided by rcu_sync_enter/exit; see the comments in
+ * percpu_down_write() and percpu_up_write().
*
* If this helper fails the callers rely on the normal rw_semaphore and
* atomic_dec_and_test(), so in this case we have the necessary barriers.
- *
- * But if it succeeds we do not have any barriers, atomic_read(write_ctr) or
- * __this_cpu_add() below can be reordered with any LOAD/STORE done by the
- * reader inside the critical section. See the comments in down_write and
- * up_write below.
*/
static bool update_fast_ctr(struct percpu_rw_semaphore *brw, unsigned int val)
{
- bool success = false;
+ bool success;
preempt_disable();
- if (likely(!atomic_read(&brw->write_ctr))) {
+ success = rcu_sync_is_idle(&brw->rss);
+ if (likely(success))
__this_cpu_add(*brw->fast_read_ctr, val);
- success = true;
- }
preempt_enable();
return success;
void percpu_down_read(struct percpu_rw_semaphore *brw)
{
might_sleep();
- if (likely(update_fast_ctr(brw, +1))) {
- rwsem_acquire_read(&brw->rw_sem.dep_map, 0, 0, _RET_IP_);
+ rwsem_acquire_read(&brw->rw_sem.dep_map, 0, 0, _RET_IP_);
+
+ if (likely(update_fast_ctr(brw, +1)))
return;
- }
- down_read(&brw->rw_sem);
+ /* Avoid rwsem_acquire_read() and rwsem_release() */
+ __down_read(&brw->rw_sem);
atomic_inc(&brw->slow_read_ctr);
- /* avoid up_read()->rwsem_release() */
__up_read(&brw->rw_sem);
}
+EXPORT_SYMBOL_GPL(percpu_down_read);
int percpu_down_read_trylock(struct percpu_rw_semaphore *brw)
{
if (atomic_dec_and_test(&brw->slow_read_ctr))
wake_up_all(&brw->write_waitq);
}
+EXPORT_SYMBOL_GPL(percpu_up_read);
static int clear_fast_ctr(struct percpu_rw_semaphore *brw)
{
return sum;
}
-/*
- * A writer increments ->write_ctr to force the readers to switch to the
- * slow mode, note the atomic_read() check in update_fast_ctr().
- *
- * After that the readers can only inc/dec the slow ->slow_read_ctr counter,
- * ->fast_read_ctr is stable. Once the writer moves its sum into the slow
- * counter it represents the number of active readers.
- *
- * Finally the writer takes ->rw_sem for writing and blocks the new readers,
- * then waits until the slow counter becomes zero.
- */
void percpu_down_write(struct percpu_rw_semaphore *brw)
{
- /* tell update_fast_ctr() there is a pending writer */
- atomic_inc(&brw->write_ctr);
/*
- * 1. Ensures that write_ctr != 0 is visible to any down_read/up_read
- * so that update_fast_ctr() can't succeed.
- *
- * 2. Ensures we see the result of every previous this_cpu_add() in
- * update_fast_ctr().
+ * Make rcu_sync_is_idle() == F and thus disable the fast-path in
+ * percpu_down_read() and percpu_up_read(), and wait for gp pass.
*
- * 3. Ensures that if any reader has exited its critical section via
- * fast-path, it executes a full memory barrier before we return.
- * See R_W case in the comment above update_fast_ctr().
+ * The latter synchronises us with the preceding readers which used
+ * the fast-past, so we can not miss the result of __this_cpu_add()
+ * or anything else inside their criticial sections.
*/
- synchronize_sched_expedited();
+ rcu_sync_enter(&brw->rss);
/* exclude other writers, and block the new readers completely */
down_write(&brw->rw_sem);
/* wait for all readers to complete their percpu_up_read() */
wait_event(brw->write_waitq, !atomic_read(&brw->slow_read_ctr));
}
+EXPORT_SYMBOL_GPL(percpu_down_write);
void percpu_up_write(struct percpu_rw_semaphore *brw)
{
/* release the lock, but the readers can't use the fast-path */
up_write(&brw->rw_sem);
/*
- * Insert the barrier before the next fast-path in down_read,
- * see W_R case in the comment above update_fast_ctr().
+ * Enable the fast-path in percpu_down_read() and percpu_up_read()
+ * but only after another gp pass; this adds the necessary barrier
+ * to ensure the reader can't miss the changes done by us.
*/
- synchronize_sched_expedited();
- /* the last writer unblocks update_fast_ctr() */
- atomic_dec(&brw->write_ctr);
+ rcu_sync_exit(&brw->rss);
}
+EXPORT_SYMBOL_GPL(percpu_up_write);
-obj-y += update.o
+obj-y += update.o sync.o
obj-$(CONFIG_SRCU) += srcu.o
obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
obj-$(CONFIG_TREE_RCU) += tree.o
#define RCUTORTURE_TASKS_OPS
-static bool torturing_tasks(void)
+static bool __maybe_unused torturing_tasks(void)
{
return false;
}
}
call_rcu_time = jiffies;
}
- cond_resched_rcu_qs();
stutter_wait("rcu_torture_boost");
if (torture_must_stop())
goto checkwait;
__this_cpu_inc(rcu_torture_batch[completed]);
preempt_enable();
cur_ops->readunlock(idx);
- cond_resched_rcu_qs();
stutter_wait("rcu_torture_reader");
} while (!torture_must_stop());
if (irqreader && cur_ops->irq_capable) {
for (i = 0; i < ARRAY_SIZE(torture_ops); i++)
pr_alert(" %s", torture_ops[i]->name);
pr_alert("\n");
- torture_init_end();
- return -EINVAL;
+ firsterr = -EINVAL;
+ goto unwind;
}
if (cur_ops->fqs == NULL && fqs_duration != 0) {
pr_alert("rcu-torture: ->fqs NULL and non-zero fqs_duration, fqs disabled.\n");
fqs_duration = 0;
}
if (cur_ops->init)
- cur_ops->init(); /* no "goto unwind" prior to this point!!! */
+ cur_ops->init();
if (nreaders >= 0) {
nrealreaders = nreaders;
--- /dev/null
+/*
+ * RCU-based infrastructure for lightweight reader-writer locking
+ *
+ * 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) 2015, Red Hat, Inc.
+ *
+ * Author: Oleg Nesterov <oleg@redhat.com>
+ */
+
+#include <linux/rcu_sync.h>
+#include <linux/sched.h>
+
+#ifdef CONFIG_PROVE_RCU
+#define __INIT_HELD(func) .held = func,
+#else
+#define __INIT_HELD(func)
+#endif
+
+static const struct {
+ void (*sync)(void);
+ void (*call)(struct rcu_head *, void (*)(struct rcu_head *));
+ void (*wait)(void);
+#ifdef CONFIG_PROVE_RCU
+ int (*held)(void);
+#endif
+} gp_ops[] = {
+ [RCU_SYNC] = {
+ .sync = synchronize_rcu,
+ .call = call_rcu,
+ .wait = rcu_barrier,
+ __INIT_HELD(rcu_read_lock_held)
+ },
+ [RCU_SCHED_SYNC] = {
+ .sync = synchronize_sched,
+ .call = call_rcu_sched,
+ .wait = rcu_barrier_sched,
+ __INIT_HELD(rcu_read_lock_sched_held)
+ },
+ [RCU_BH_SYNC] = {
+ .sync = synchronize_rcu_bh,
+ .call = call_rcu_bh,
+ .wait = rcu_barrier_bh,
+ __INIT_HELD(rcu_read_lock_bh_held)
+ },
+};
+
+enum { GP_IDLE = 0, GP_PENDING, GP_PASSED };
+enum { CB_IDLE = 0, CB_PENDING, CB_REPLAY };
+
+#define rss_lock gp_wait.lock
+
+#ifdef CONFIG_PROVE_RCU
+void rcu_sync_lockdep_assert(struct rcu_sync *rsp)
+{
+ RCU_LOCKDEP_WARN(!gp_ops[rsp->gp_type].held(),
+ "suspicious rcu_sync_is_idle() usage");
+}
+#endif
+
+/**
+ * rcu_sync_init() - Initialize an rcu_sync structure
+ * @rsp: Pointer to rcu_sync structure to be initialized
+ * @type: Flavor of RCU with which to synchronize rcu_sync structure
+ */
+void rcu_sync_init(struct rcu_sync *rsp, enum rcu_sync_type type)
+{
+ memset(rsp, 0, sizeof(*rsp));
+ init_waitqueue_head(&rsp->gp_wait);
+ rsp->gp_type = type;
+}
+
+/**
+ * rcu_sync_enter() - Force readers onto slowpath
+ * @rsp: Pointer to rcu_sync structure to use for synchronization
+ *
+ * This function is used by updaters who need readers to make use of
+ * a slowpath during the update. After this function returns, all
+ * subsequent calls to rcu_sync_is_idle() will return false, which
+ * tells readers to stay off their fastpaths. A later call to
+ * rcu_sync_exit() re-enables reader slowpaths.
+ *
+ * When called in isolation, rcu_sync_enter() must wait for a grace
+ * period, however, closely spaced calls to rcu_sync_enter() can
+ * optimize away the grace-period wait via a state machine implemented
+ * by rcu_sync_enter(), rcu_sync_exit(), and rcu_sync_func().
+ */
+void rcu_sync_enter(struct rcu_sync *rsp)
+{
+ bool need_wait, need_sync;
+
+ spin_lock_irq(&rsp->rss_lock);
+ need_wait = rsp->gp_count++;
+ need_sync = rsp->gp_state == GP_IDLE;
+ if (need_sync)
+ rsp->gp_state = GP_PENDING;
+ spin_unlock_irq(&rsp->rss_lock);
+
+ BUG_ON(need_wait && need_sync);
+
+ if (need_sync) {
+ gp_ops[rsp->gp_type].sync();
+ rsp->gp_state = GP_PASSED;
+ wake_up_all(&rsp->gp_wait);
+ } else if (need_wait) {
+ wait_event(rsp->gp_wait, rsp->gp_state == GP_PASSED);
+ } else {
+ /*
+ * Possible when there's a pending CB from a rcu_sync_exit().
+ * Nobody has yet been allowed the 'fast' path and thus we can
+ * avoid doing any sync(). The callback will get 'dropped'.
+ */
+ BUG_ON(rsp->gp_state != GP_PASSED);
+ }
+}
+
+/**
+ * rcu_sync_func() - Callback function managing reader access to fastpath
+ * @rsp: Pointer to rcu_sync structure to use for synchronization
+ *
+ * This function is passed to one of the call_rcu() functions by
+ * rcu_sync_exit(), so that it is invoked after a grace period following the
+ * that invocation of rcu_sync_exit(). It takes action based on events that
+ * have taken place in the meantime, so that closely spaced rcu_sync_enter()
+ * and rcu_sync_exit() pairs need not wait for a grace period.
+ *
+ * If another rcu_sync_enter() is invoked before the grace period
+ * ended, reset state to allow the next rcu_sync_exit() to let the
+ * readers back onto their fastpaths (after a grace period). If both
+ * another rcu_sync_enter() and its matching rcu_sync_exit() are invoked
+ * before the grace period ended, re-invoke call_rcu() on behalf of that
+ * rcu_sync_exit(). Otherwise, set all state back to idle so that readers
+ * can again use their fastpaths.
+ */
+static void rcu_sync_func(struct rcu_head *rcu)
+{
+ struct rcu_sync *rsp = container_of(rcu, struct rcu_sync, cb_head);
+ unsigned long flags;
+
+ BUG_ON(rsp->gp_state != GP_PASSED);
+ BUG_ON(rsp->cb_state == CB_IDLE);
+
+ spin_lock_irqsave(&rsp->rss_lock, flags);
+ if (rsp->gp_count) {
+ /*
+ * A new rcu_sync_begin() has happened; drop the callback.
+ */
+ rsp->cb_state = CB_IDLE;
+ } else if (rsp->cb_state == CB_REPLAY) {
+ /*
+ * A new rcu_sync_exit() has happened; requeue the callback
+ * to catch a later GP.
+ */
+ rsp->cb_state = CB_PENDING;
+ gp_ops[rsp->gp_type].call(&rsp->cb_head, rcu_sync_func);
+ } else {
+ /*
+ * We're at least a GP after rcu_sync_exit(); eveybody will now
+ * have observed the write side critical section. Let 'em rip!.
+ */
+ rsp->cb_state = CB_IDLE;
+ rsp->gp_state = GP_IDLE;
+ }
+ spin_unlock_irqrestore(&rsp->rss_lock, flags);
+}
+
+/**
+ * rcu_sync_exit() - Allow readers back onto fast patch after grace period
+ * @rsp: Pointer to rcu_sync structure to use for synchronization
+ *
+ * This function is used by updaters who have completed, and can therefore
+ * now allow readers to make use of their fastpaths after a grace period
+ * has elapsed. After this grace period has completed, all subsequent
+ * calls to rcu_sync_is_idle() will return true, which tells readers that
+ * they can once again use their fastpaths.
+ */
+void rcu_sync_exit(struct rcu_sync *rsp)
+{
+ spin_lock_irq(&rsp->rss_lock);
+ if (!--rsp->gp_count) {
+ if (rsp->cb_state == CB_IDLE) {
+ rsp->cb_state = CB_PENDING;
+ gp_ops[rsp->gp_type].call(&rsp->cb_head, rcu_sync_func);
+ } else if (rsp->cb_state == CB_PENDING) {
+ rsp->cb_state = CB_REPLAY;
+ }
+ }
+ spin_unlock_irq(&rsp->rss_lock);
+}
+
+/**
+ * rcu_sync_dtor() - Clean up an rcu_sync structure
+ * @rsp: Pointer to rcu_sync structure to be cleaned up
+ */
+void rcu_sync_dtor(struct rcu_sync *rsp)
+{
+ int cb_state;
+
+ BUG_ON(rsp->gp_count);
+
+ spin_lock_irq(&rsp->rss_lock);
+ if (rsp->cb_state == CB_REPLAY)
+ rsp->cb_state = CB_PENDING;
+ cb_state = rsp->cb_state;
+ spin_unlock_irq(&rsp->rss_lock);
+
+ if (cb_state != CB_IDLE) {
+ gp_ops[rsp->gp_type].wait();
+ BUG_ON(rsp->cb_state != CB_IDLE);
+ }
+}
*/
void stutter_wait(const char *title)
{
+ cond_resched_rcu_qs();
while (READ_ONCE(stutter_pause_test) ||
(torture_runnable && !READ_ONCE(*torture_runnable))) {
if (stutter_pause_test)
while test $# -gt 0
do
case "$1" in
- --bootargs)
+ --bootargs|--bootarg)
checkarg --bootargs "(list of kernel boot arguments)" "$#" "$2" '.*' '^--'
TORTURE_BOOTARGS="$2"
shift
--buildonly)
TORTURE_BUILDONLY=1
;;
- --configs)
+ --configs|--config)
checkarg --configs "(list of config files)" "$#" "$2" '^[^/]*$' '^--'
configs="$2"
shift
--no-initrd)
TORTURE_INITRD=""; export TORTURE_INITRD
;;
- --qemu-args)
+ --qemu-args|--qemu-arg)
checkarg --qemu-args "-qemu args" $# "$2" '^-' '^error'
TORTURE_QEMU_ARG="$2"
shift
LOCK01
LOCK02
LOCK03
-LOCK04
\ No newline at end of file
+LOCK04
+LOCK05
+LOCK06
--- /dev/null
+CONFIG_SMP=y
+CONFIG_NR_CPUS=4
+CONFIG_HOTPLUG_CPU=y
+CONFIG_PREEMPT_NONE=n
+CONFIG_PREEMPT_VOLUNTARY=n
+CONFIG_PREEMPT=y
--- /dev/null
+locktorture.torture_type=rtmutex_lock
--- /dev/null
+CONFIG_SMP=y
+CONFIG_NR_CPUS=4
+CONFIG_HOTPLUG_CPU=y
+CONFIG_PREEMPT_NONE=n
+CONFIG_PREEMPT_VOLUNTARY=n
+CONFIG_PREEMPT=y
--- /dev/null
+locktorture.torture_type=percpu_rwsem_lock
projects / linux-beck.git / commitdiff