* 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 RCU_MB
+#ifdef RCU_MEMBARRIER
static int init_done;
+int has_sys_membarrier;
void __attribute__((constructor)) rcu_init(void);
-void __attribute__((destructor)) rcu_exit(void);
-#else
+#endif
+
+#ifdef RCU_MB
void rcu_init(void)
{
}
#endif
-static pthread_mutex_t rcu_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;
static LIST_HEAD(registry);
-static void internal_rcu_lock(void)
+static void mutex_lock(pthread_mutex_t *mutex)
{
int ret;
#ifndef DISTRUST_SIGNALS_EXTREME
- ret = pthread_mutex_lock(&rcu_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(&rcu_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");
#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
}
-static void internal_rcu_unlock(void)
+static void mutex_unlock(pthread_mutex_t *mutex)
{
int ret;
- ret = pthread_mutex_unlock(&rcu_mutex);
+ ret = pthread_mutex_unlock(mutex);
if (ret) {
perror("Error in pthread mutex unlock");
exit(-1);
}
/*
- * called with rcu_mutex held.
+ * called with rcu_gp_lock held.
*/
static void switch_next_rcu_qparity(void)
{
STORE_SHARED(rcu_gp_ctr, rcu_gp_ctr ^ RCU_GP_CTR_PHASE);
}
-#ifdef RCU_MB
-#if 0 /* unused */
-static void force_mb_single_thread(struct rcu_reader *index)
+#ifdef RCU_MEMBARRIER
+static void smp_mb_heavy(void)
{
- smp_mb();
+ if (likely(has_sys_membarrier))
+ membarrier(MEMBARRIER_EXPEDITED);
+ else
+ smp_mb();
}
-#endif //0
+#endif
-static void force_mb_all_threads(void)
-{
- smp_mb();
-}
-#else /* #ifdef RCU_MB */
-#if 0 /* unused */
-static void force_mb_single_thread(struct rcu_reader *index)
+#ifdef RCU_MB
+static void smp_mb_heavy(void)
{
- 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, SIGRCU);
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 rcu_reader *index;
}
smp_mb(); /* read ->need_mb before ending the barrier */
}
-#endif /* #else #ifdef RCU_MB */
+
+static void smp_mb_heavy(void)
+{
+ 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_heavy();
if (uatomic_read(&gp_futex) == -1)
futex_async(&gp_futex, FUTEX_WAIT, -1,
NULL, NULL, 0);
if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
uatomic_dec(&gp_futex);
/* Write futex before read reader_gp */
- force_mb_all_threads();
+ smp_mb_heavy();
}
list_for_each_entry_safe(index, tmp, ®istry, head) {
if (list_empty(®istry)) {
if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
/* Read reader_gp before write futex */
- force_mb_all_threads();
+ smp_mb_heavy();
uatomic_set(&gp_futex, 0);
}
break;
if (list_empty(®istry)) {
if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
/* Read reader_gp before write futex */
- force_mb_all_threads();
+ smp_mb_heavy();
uatomic_set(&gp_futex, 0);
}
break;
wait_gp();
break; /* only escape switch */
case KICK_READER_LOOPS:
- force_mb_all_threads();
+ smp_mb_heavy();
wait_loops = 0;
break; /* only escape switch */
default:
void synchronize_rcu(void)
{
- internal_rcu_lock();
+ mutex_lock(&rcu_gp_lock);
/* All threads should read qparity before accessing data structure
- * where new ptr points to. Must be done within internal_rcu_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();
+ smp_mb_heavy();
switch_next_rcu_qparity(); /* 0 -> 1 */
wait_for_quiescent_state(); /* Wait readers in parity 1 */
/* Finish waiting for reader threads before letting the old ptr being
- * freed. Must be done within internal_rcu_lock because it iterates on
- * reader threads. */
- force_mb_all_threads();
+ * freed. Must be done within rcu_gp_lock because it iterates on reader
+ * threads. */
+ smp_mb_heavy();
- internal_rcu_unlock();
+ mutex_unlock(&rcu_gp_lock);
}
/*
assert(rcu_reader.need_mb == 0);
assert(rcu_reader.ctr == 0);
- internal_rcu_lock();
+ mutex_lock(&rcu_gp_lock);
rcu_init(); /* In case gcc does not support constructor attribute */
list_add(&rcu_reader.head, ®istry);
- internal_rcu_unlock();
+ mutex_unlock(&rcu_gp_lock);
}
void rcu_unregister_thread(void)
{
- internal_rcu_lock();
+ mutex_lock(&rcu_gp_lock);
list_del(&rcu_reader.head);
- internal_rcu_unlock();
+ mutex_unlock(&rcu_gp_lock);
+}
+
+#ifdef RCU_MEMBARRIER
+void rcu_init(void)
+{
+ if (init_done)
+ return;
+ init_done = 1;
+ if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY))
+ has_sys_membarrier = 1;
}
+#endif
-#ifndef RCU_MB
+#ifdef RCU_SIGNAL
static void sigrcu_handler(int signo, siginfo_t *siginfo, void *context)
{
/*
* 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_rcu_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 rcu_init(void)
{
assert(act.sa_sigaction == sigrcu_handler);
assert(list_empty(®istry));
}
-#endif /* #ifndef RCU_MB */
+#endif /* #ifdef RCU_SIGNAL */
projects / urcu.git / blobdiff