*
* Userspace RCU library
*
- * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
+ * Copyright (c) 2009 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
* Copyright (c) 2009 Paul E. McKenney, IBM Corporation.
*
* This library is free software; you can redistribute it and/or
* IBM's contributions to this file may be relicensed under LGPLv2 or later.
*/
+#define _BSD_SOURCE
#include <stdio.h>
#include <pthread.h>
#include <signal.h>
/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
#include "urcu.h"
-#ifndef URCU_MB
+#ifdef RCU_MEMBARRIER
static int init_done;
+int has_sys_membarrier;
-void __attribute__((constructor)) urcu_init(void);
-void __attribute__((destructor)) urcu_exit(void);
-#else
-void urcu_init(void)
+void __attribute__((constructor)) rcu_init(void);
+#endif
+
+#ifdef RCU_MB
+void rcu_init(void)
{
}
#endif
-static pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER;
+#ifdef RCU_SIGNAL
+static int init_done;
+
+void __attribute__((constructor)) rcu_init(void);
+void __attribute__((destructor)) rcu_exit(void);
+#endif
+
+static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
int gp_futex;
/*
* Global grace period counter.
- * Contains the current RCU_GP_CTR_BIT.
+ * Contains the current RCU_GP_CTR_PHASE.
* Also has a RCU_GP_COUNT of 1, to accelerate the reader fast path.
* Written to only by writer with mutex taken. Read by both writer and readers.
*/
-long urcu_gp_ctr = RCU_GP_COUNT;
+unsigned long rcu_gp_ctr = RCU_GP_COUNT;
/*
* Written to only by each individual reader. Read by both the reader and the
* writers.
*/
-struct urcu_reader __thread urcu_reader;
+struct rcu_reader __thread rcu_reader;
#ifdef DEBUG_YIELD
unsigned int yield_active;
static LIST_HEAD(registry);
-static void internal_urcu_lock(void)
+static void mutex_lock(pthread_mutex_t *mutex)
{
int ret;
#ifndef DISTRUST_SIGNALS_EXTREME
- ret = pthread_mutex_lock(&urcu_mutex);
+ ret = pthread_mutex_lock(mutex);
if (ret) {
perror("Error in pthread mutex lock");
exit(-1);
}
#else /* #ifndef DISTRUST_SIGNALS_EXTREME */
- while ((ret = pthread_mutex_trylock(&urcu_mutex)) != 0) {
+ while ((ret = pthread_mutex_trylock(mutex)) != 0) {
if (ret != EBUSY && ret != EINTR) {
printf("ret = %d, errno = %d\n", ret, errno);
perror("Error in pthread mutex lock");
exit(-1);
}
- if (urcu_reader.need_mb) {
+ if (LOAD_SHARED(rcu_reader.need_mb)) {
smp_mb();
- urcu_reader.need_mb = 0;
+ _STORE_SHARED(rcu_reader.need_mb, 0);
smp_mb();
}
poll(NULL,0,10);
#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
}
-static void internal_urcu_unlock(void)
+static void mutex_unlock(pthread_mutex_t *mutex)
{
int ret;
- ret = pthread_mutex_unlock(&urcu_mutex);
+ ret = pthread_mutex_unlock(mutex);
if (ret) {
perror("Error in pthread mutex unlock");
exit(-1);
}
}
-/*
- * called with urcu_mutex held.
- */
-static void switch_next_urcu_qparity(void)
-{
- STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr ^ RCU_GP_CTR_BIT);
-}
-
-#ifdef URCU_MB
-#if 0 /* unused */
-static void force_mb_single_thread(struct urcu_reader *index)
+#ifdef RCU_MEMBARRIER
+static void smp_mb_master(int group)
{
- smp_mb();
+ if (likely(has_sys_membarrier))
+ membarrier(MEMBARRIER_EXPEDITED);
+ else
+ smp_mb();
}
-#endif //0
+#endif
-static void force_mb_all_threads(void)
+#ifdef RCU_MB
+static void smp_mb_master(int group)
{
smp_mb();
}
-#else /* #ifdef URCU_MB */
-#if 0 /* unused */
-static void force_mb_single_thread(struct urcu_reader *index)
-{
- assert(!list_empty(®istry));
- /*
- * pthread_kill has a smp_mb(). But beware, we assume it performs
- * a cache flush on architectures with non-coherent cache. Let's play
- * safe and don't assume anything : we use smp_mc() to make sure the
- * cache flush is enforced.
- */
- index->need_mb = 1;
- smp_mc(); /* write ->need_mb before sending the signals */
- pthread_kill(index->tid, SIGURCU);
- smp_mb();
- /*
- * Wait for sighandler (and thus mb()) to execute on every thread.
- * BUSY-LOOP.
- */
- while (index->need_mb) {
- poll(NULL, 0, 1);
- }
- smp_mb(); /* read ->need_mb before ending the barrier */
-}
-#endif //0
+#endif
-static void force_mb_all_threads(void)
+#ifdef RCU_SIGNAL
+static void force_mb_all_readers(void)
{
- struct urcu_reader *index;
+ struct rcu_reader *index;
/*
* Ask for each threads to execute a smp_mb() so we can consider the
* safe and don't assume anything : we use smp_mc() to make sure the
* cache flush is enforced.
*/
- list_for_each_entry(index, ®istry, head) {
- index->need_mb = 1;
- smp_mc(); /* write need_mb before sending the signal */
- pthread_kill(index->tid, SIGURCU);
+ list_for_each_entry(index, ®istry, node) {
+ STORE_SHARED(index->need_mb, 1);
+ pthread_kill(index->tid, SIGRCU);
}
/*
* Wait for sighandler (and thus mb()) to execute on every thread.
* relevant bug report. For Linux kernels, we recommend getting
* the Linux Test Project (LTP).
*/
- list_for_each_entry(index, ®istry, head) {
- while (index->need_mb) {
- pthread_kill(index->tid, SIGURCU);
+ list_for_each_entry(index, ®istry, node) {
+ while (LOAD_SHARED(index->need_mb)) {
+ pthread_kill(index->tid, SIGRCU);
poll(NULL, 0, 1);
}
}
smp_mb(); /* read ->need_mb before ending the barrier */
}
-#endif /* #else #ifdef URCU_MB */
+
+static void smp_mb_master(int group)
+{
+ force_mb_all_readers();
+}
+#endif /* #ifdef RCU_SIGNAL */
/*
* synchronize_rcu() waiting. Single thread.
static void wait_gp(void)
{
/* Read reader_gp before read futex */
- force_mb_all_threads();
+ smp_mb_master(RCU_MB_GROUP);
if (uatomic_read(&gp_futex) == -1)
- futex(&gp_futex, FUTEX_WAIT, -1,
+ futex_async(&gp_futex, FUTEX_WAIT, -1,
NULL, NULL, 0);
}
-void wait_for_quiescent_state(void)
+void update_counter_and_wait(void)
{
LIST_HEAD(qsreaders);
int wait_loops = 0;
- struct urcu_reader *index, *tmp;
+ struct rcu_reader *index, *tmp;
+
+ /* Switch parity: 0 -> 1, 1 -> 0 */
+ STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
- if (list_empty(®istry))
- return;
/*
- * Wait for each thread urcu_reader.ctr count to become 0.
+ * Must commit rcu_gp_ctr update to memory before waiting for quiescent
+ * state. Failure to do so could result in the writer waiting forever
+ * while new readers are always accessing data (no progress). Enforce
+ * compiler-order of store to rcu_gp_ctr before load rcu_reader ctr.
+ */
+ barrier();
+
+ /*
+ *
+ * Adding a smp_mb() which is _not_ formally required, but makes the
+ * model easier to understand. It does not have a big performance impact
+ * anyway, given this is the write-side.
+ */
+ smp_mb();
+
+ /*
+ * Wait for each thread rcu_reader.ctr count to become 0.
*/
for (;;) {
wait_loops++;
if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
uatomic_dec(&gp_futex);
/* Write futex before read reader_gp */
- force_mb_all_threads();
+ smp_mb_master(RCU_MB_GROUP);
}
- list_for_each_entry_safe(index, tmp, ®istry, head) {
- if (!rcu_old_gp_ongoing(&index->ctr))
- list_move(&index->head, &qsreaders);
+ list_for_each_entry_safe(index, tmp, ®istry, node) {
+ if (!rcu_gp_ongoing(&index->ctr))
+ list_move(&index->node, &qsreaders);
}
#ifndef HAS_INCOHERENT_CACHES
if (list_empty(®istry)) {
if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
/* Read reader_gp before write futex */
- force_mb_all_threads();
+ smp_mb_master(RCU_MB_GROUP);
uatomic_set(&gp_futex, 0);
}
break;
#else /* #ifndef HAS_INCOHERENT_CACHES */
/*
* BUSY-LOOP. Force the reader thread to commit its
- * urcu_reader.ctr update to memory if we wait for too long.
+ * rcu_reader.ctr update to memory if we wait for too long.
*/
if (list_empty(®istry)) {
if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
/* Read reader_gp before write futex */
- force_mb_all_threads();
+ smp_mb_master(RCU_MB_GROUP);
uatomic_set(&gp_futex, 0);
}
break;
wait_gp();
break; /* only escape switch */
case KICK_READER_LOOPS:
- force_mb_all_threads();
+ smp_mb_master(RCU_MB_GROUP);
wait_loops = 0;
break; /* only escape switch */
default:
void synchronize_rcu(void)
{
- internal_urcu_lock();
+ mutex_lock(&rcu_gp_lock);
+
+ if (list_empty(®istry))
+ goto out;
/* All threads should read qparity before accessing data structure
- * where new ptr points to. Must be done within internal_urcu_lock
- * because it iterates on reader threads.*/
+ * where new ptr points to. Must be done within rcu_gp_lock because it
+ * iterates on reader threads.*/
/* Write new ptr before changing the qparity */
- force_mb_all_threads();
-
- switch_next_urcu_qparity(); /* 0 -> 1 */
-
- /*
- * Must commit qparity update to memory before waiting for parity
- * 0 quiescent state. Failure to do so could result in the writer
- * waiting forever while new readers are always accessing data (no
- * progress).
- * Ensured by STORE_SHARED and LOAD_SHARED.
- */
-
- /*
- * Adding a smp_mb() which is _not_ formally required, but makes the
- * model easier to understand. It does not have a big performance impact
- * anyway, given this is the write-side.
- */
- smp_mb();
+ smp_mb_master(RCU_MB_GROUP);
/*
* Wait for previous parity to be empty of readers.
*/
- wait_for_quiescent_state(); /* Wait readers in parity 0 */
+ update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */
/*
* Must finish waiting for quiescent state for parity 0 before
- * committing qparity update to memory. Failure to do so could result in
- * the writer waiting forever while new readers are always accessing
- * data (no progress).
- * Ensured by STORE_SHARED and LOAD_SHARED.
- */
-
- /*
- * Adding a smp_mb() which is _not_ formally required, but makes the
- * model easier to understand. It does not have a big performance impact
- * anyway, given this is the write-side.
- */
- smp_mb();
-
- switch_next_urcu_qparity(); /* 1 -> 0 */
-
- /*
- * Must commit qparity update to memory before waiting for parity
- * 1 quiescent state. Failure to do so could result in the writer
- * waiting forever while new readers are always accessing data (no
- * progress).
- * Ensured by STORE_SHARED and LOAD_SHARED.
+ * committing next rcu_gp_ctr update to memory. Failure to do so could
+ * result in the writer waiting forever while new readers are always
+ * accessing data (no progress). Enforce compiler-order of load
+ * rcu_reader ctr before store to rcu_gp_ctr.
*/
+ barrier();
/*
* Adding a smp_mb() which is _not_ formally required, but makes the
/*
* Wait for previous parity to be empty of readers.
*/
- wait_for_quiescent_state(); /* Wait readers in parity 1 */
+ update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */
/* Finish waiting for reader threads before letting the old ptr being
- * freed. Must be done within internal_urcu_lock because it iterates on
- * reader threads. */
- force_mb_all_threads();
-
- internal_urcu_unlock();
+ * freed. Must be done within rcu_gp_lock because it iterates on reader
+ * threads. */
+ smp_mb_master(RCU_MB_GROUP);
+out:
+ mutex_unlock(&rcu_gp_lock);
}
/*
_rcu_read_unlock();
}
-void *rcu_dereference(void *p)
-{
- return _rcu_dereference(p);
-}
-
-void *rcu_assign_pointer_sym(void **p, void *v)
-{
- wmb();
- return STORE_SHARED(p, v);
-}
-
-void *rcu_xchg_pointer_sym(void **p, void *v)
-{
- wmb();
- return uatomic_xchg(p, v);
-}
-
-void *rcu_cmpxchg_pointer_sym(void **p, void *old, void *_new)
-{
- wmb();
- return uatomic_cmpxchg(p, old, _new);
-}
-
-void *rcu_publish_content_sym(void **p, void *v)
+void rcu_register_thread(void)
{
- void *oldptr;
-
- oldptr = _rcu_xchg_pointer(p, v);
- synchronize_rcu();
- return oldptr;
+ rcu_reader.tid = pthread_self();
+ assert(rcu_reader.need_mb == 0);
+ assert(!(rcu_reader.ctr & RCU_GP_CTR_NEST_MASK));
+
+ mutex_lock(&rcu_gp_lock);
+ rcu_init(); /* In case gcc does not support constructor attribute */
+ list_add(&rcu_reader.node, ®istry);
+ mutex_unlock(&rcu_gp_lock);
}
-void rcu_register_thread(void)
+void rcu_unregister_thread(void)
{
- urcu_reader.tid = pthread_self();
- assert(urcu_reader.need_mb == 0);
- assert(urcu_reader.ctr == 0);
-
- internal_urcu_lock();
- urcu_init(); /* In case gcc does not support constructor attribute */
- list_add(&urcu_reader.head, ®istry);
- internal_urcu_unlock();
+ mutex_lock(&rcu_gp_lock);
+ list_del(&rcu_reader.node);
+ mutex_unlock(&rcu_gp_lock);
}
-void rcu_unregister_thread(void)
+#ifdef RCU_MEMBARRIER
+void rcu_init(void)
{
- internal_urcu_lock();
- list_del(&urcu_reader.head);
- internal_urcu_unlock();
+ if (init_done)
+ return;
+ init_done = 1;
+ if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY))
+ has_sys_membarrier = 1;
}
+#endif
-#ifndef URCU_MB
-static void sigurcu_handler(int signo, siginfo_t *siginfo, void *context)
+#ifdef RCU_SIGNAL
+static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context)
{
/*
* Executing this smp_mb() is the only purpose of this signal handler.
* executed on.
*/
smp_mb();
- urcu_reader.need_mb = 0;
+ _STORE_SHARED(rcu_reader.need_mb, 0);
smp_mb();
}
/*
- * urcu_init constructor. Called when the library is linked, but also when
+ * rcu_init constructor. Called when the library is linked, but also when
* reader threads are calling rcu_register_thread().
* Should only be called by a single thread at a given time. This is ensured by
- * holing the internal_urcu_lock() from rcu_register_thread() or by running at
- * library load time, which should not be executed by multiple threads nor
- * concurrently with rcu_register_thread() anyway.
+ * holing the rcu_gp_lock from rcu_register_thread() or by running at library
+ * load time, which should not be executed by multiple threads nor concurrently
+ * with rcu_register_thread() anyway.
*/
-void urcu_init(void)
+void rcu_init(void)
{
struct sigaction act;
int ret;
return;
init_done = 1;
- act.sa_sigaction = sigurcu_handler;
+ act.sa_sigaction = sigrcu_handler;
act.sa_flags = SA_SIGINFO | SA_RESTART;
sigemptyset(&act.sa_mask);
- ret = sigaction(SIGURCU, &act, NULL);
+ ret = sigaction(SIGRCU, &act, NULL);
if (ret) {
perror("Error in sigaction");
exit(-1);
}
}
-void urcu_exit(void)
+void rcu_exit(void)
{
struct sigaction act;
int ret;
- ret = sigaction(SIGURCU, NULL, &act);
+ ret = sigaction(SIGRCU, NULL, &act);
if (ret) {
perror("Error in sigaction");
exit(-1);
}
- assert(act.sa_sigaction == sigurcu_handler);
+ assert(act.sa_sigaction == sigrcu_handler);
assert(list_empty(®istry));
}
-#endif /* #ifndef URCU_MB */
+#endif /* #ifdef RCU_SIGNAL */
projects / urcu.git / blobdiff