#define _BSD_SOURCE
#define _GNU_SOURCE
#define _LGPL_SOURCE
+#define _DEFAULT_SOURCE
#include <stdio.h>
#include <pthread.h>
#include <signal.h>
#include <errno.h>
#include <poll.h>
+#include "urcu/arch.h"
#include "urcu/wfcqueue.h"
#include "urcu/map/urcu.h"
#include "urcu/static/urcu.h"
*/
#define RCU_QS_ACTIVE_ATTEMPTS 100
-/*
- * RCU_MEMBARRIER is only possibly available on Linux.
- */
-#if defined(RCU_MEMBARRIER) && defined(__linux__)
-#include <urcu/syscall-compat.h>
-#endif
-
-/* If the headers do not support SYS_membarrier, fall back on RCU_MB */
-#ifdef SYS_membarrier
-# define membarrier(...) syscall(SYS_membarrier, __VA_ARGS__)
+/* If the headers do not support membarrier system call, fall back on RCU_MB */
+#ifdef __NR_membarrier
+# define membarrier(...) syscall(__NR_membarrier, __VA_ARGS__)
#else
# define membarrier(...) -ENOSYS
#endif
-#define MEMBARRIER_EXPEDITED (1 << 0)
-#define MEMBARRIER_DELAYED (1 << 1)
-#define MEMBARRIER_QUERY (1 << 16)
+enum membarrier_cmd {
+ MEMBARRIER_CMD_QUERY = 0,
+ MEMBARRIER_CMD_SHARED = (1 << 0),
+};
#ifdef RCU_MEMBARRIER
static int init_done;
void __attribute__((destructor)) rcu_exit(void);
#endif
+/*
+ * rcu_gp_lock ensures mutual exclusion between threads calling
+ * synchronize_rcu().
+ */
static pthread_mutex_t rcu_gp_lock = PTHREAD_MUTEX_INITIALIZER;
+/*
+ * rcu_registry_lock ensures mutual exclusion between threads
+ * registering and unregistering themselves to/from the registry, and
+ * with threads reading that registry from synchronize_rcu(). However,
+ * this lock is not held all the way through the completion of awaiting
+ * for the grace period. It is sporadically released between iterations
+ * on the registry.
+ * rcu_registry_lock may nest inside rcu_gp_lock.
+ */
+static pthread_mutex_t rcu_registry_lock = PTHREAD_MUTEX_INITIALIZER;
struct rcu_gp rcu_gp = { .ctr = RCU_GP_COUNT };
/*
_CMM_STORE_SHARED(URCU_TLS(rcu_reader).need_mb, 0);
cmm_smp_mb();
}
- poll(NULL,0,10);
+ (void) poll(NULL, 0, 10);
}
#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
}
}
#ifdef RCU_MEMBARRIER
-static void smp_mb_master(int group)
+static void smp_mb_master(void)
{
if (caa_likely(rcu_has_sys_membarrier))
- (void) membarrier(MEMBARRIER_EXPEDITED);
+ (void) membarrier(MEMBARRIER_CMD_SHARED, 0);
else
cmm_smp_mb();
}
#endif
#ifdef RCU_MB
-static void smp_mb_master(int group)
+static void smp_mb_master(void)
{
cmm_smp_mb();
}
cds_list_for_each_entry(index, ®istry, node) {
while (CMM_LOAD_SHARED(index->need_mb)) {
pthread_kill(index->tid, SIGRCU);
- poll(NULL, 0, 1);
+ (void) poll(NULL, 0, 1);
}
}
cmm_smp_mb(); /* read ->need_mb before ending the barrier */
}
-static void smp_mb_master(int group)
+static void smp_mb_master(void)
{
force_mb_all_readers();
}
static void wait_gp(void)
{
/* Read reader_gp before read futex */
- smp_mb_master(RCU_MB_GROUP);
- if (uatomic_read(&rcu_gp.futex) == -1)
- futex_async(&rcu_gp.futex, FUTEX_WAIT, -1,
- NULL, NULL, 0);
+ smp_mb_master();
+ if (uatomic_read(&rcu_gp.futex) != -1)
+ return;
+ while (futex_async(&rcu_gp.futex, FUTEX_WAIT, -1,
+ NULL, NULL, 0)) {
+ switch (errno) {
+ case EWOULDBLOCK:
+ /* Value already changed. */
+ return;
+ case EINTR:
+ /* Retry if interrupted by signal. */
+ break; /* Get out of switch. */
+ default:
+ /* Unexpected error. */
+ urcu_die(errno);
+ }
+ }
}
+/*
+ * Always called with rcu_registry lock held. Releases this lock between
+ * iterations and grabs it again. Holds the lock when it returns.
+ */
static void wait_for_readers(struct cds_list_head *input_readers,
struct cds_list_head *cur_snap_readers,
struct cds_list_head *qsreaders)
if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
uatomic_dec(&rcu_gp.futex);
/* Write futex before read reader_gp */
- smp_mb_master(RCU_MB_GROUP);
+ smp_mb_master();
}
cds_list_for_each_entry_safe(index, tmp, input_readers, node) {
if (cds_list_empty(input_readers)) {
if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
/* Read reader_gp before write futex */
- smp_mb_master(RCU_MB_GROUP);
+ smp_mb_master();
uatomic_set(&rcu_gp.futex, 0);
}
break;
} else {
+ /* Temporarily unlock the registry lock. */
+ mutex_unlock(&rcu_registry_lock);
if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS)
wait_gp();
else
caa_cpu_relax();
+ /* Re-lock the registry lock before the next loop. */
+ mutex_lock(&rcu_registry_lock);
}
#else /* #ifndef HAS_INCOHERENT_CACHES */
/*
if (cds_list_empty(input_readers)) {
if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
/* Read reader_gp before write futex */
- smp_mb_master(RCU_MB_GROUP);
+ smp_mb_master();
uatomic_set(&rcu_gp.futex, 0);
}
break;
} else {
if (wait_gp_loops == KICK_READER_LOOPS) {
- smp_mb_master(RCU_MB_GROUP);
+ smp_mb_master();
wait_gp_loops = 0;
}
+ /* Temporarily unlock the registry lock. */
+ mutex_unlock(&rcu_registry_lock);
if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS) {
wait_gp();
wait_gp_loops++;
} else {
caa_cpu_relax();
}
+ /* Re-lock the registry lock before the next loop. */
+ mutex_lock(&rcu_registry_lock);
}
#endif /* #else #ifndef HAS_INCOHERENT_CACHES */
}
*/
urcu_move_waiters(&waiters, &gp_waiters);
+ mutex_lock(&rcu_registry_lock);
+
if (cds_list_empty(®istry))
goto out;
- /* All threads should read qparity before accessing data structure
- * where new ptr points to. Must be done within rcu_gp_lock because it
- * iterates on reader threads.*/
+ /*
+ * All threads should read qparity before accessing data structure
+ * where new ptr points to. Must be done within rcu_registry_lock
+ * because it iterates on reader threads.
+ */
/* Write new ptr before changing the qparity */
- smp_mb_master(RCU_MB_GROUP);
+ smp_mb_master();
/*
* Wait for readers to observe original parity or be quiescent.
+ * wait_for_readers() can release and grab again rcu_registry_lock
+ * interally.
*/
wait_for_readers(®istry, &cur_snap_readers, &qsreaders);
/*
* Wait for readers to observe new parity or be quiescent.
+ * wait_for_readers() can release and grab again rcu_registry_lock
+ * interally.
*/
wait_for_readers(&cur_snap_readers, NULL, &qsreaders);
*/
cds_list_splice(&qsreaders, ®istry);
- /* Finish waiting for reader threads before letting the old ptr being
- * freed. Must be done within rcu_gp_lock because it iterates on reader
- * threads. */
- smp_mb_master(RCU_MB_GROUP);
+ /*
+ * Finish waiting for reader threads before letting the old ptr
+ * being freed. Must be done within rcu_registry_lock because it
+ * iterates on reader threads.
+ */
+ smp_mb_master();
out:
+ mutex_unlock(&rcu_registry_lock);
mutex_unlock(&rcu_gp_lock);
/*
assert(URCU_TLS(rcu_reader).need_mb == 0);
assert(!(URCU_TLS(rcu_reader).ctr & RCU_GP_CTR_NEST_MASK));
- mutex_lock(&rcu_gp_lock);
+ mutex_lock(&rcu_registry_lock);
+ assert(!URCU_TLS(rcu_reader).registered);
+ URCU_TLS(rcu_reader).registered = 1;
rcu_init(); /* In case gcc does not support constructor attribute */
cds_list_add(&URCU_TLS(rcu_reader).node, ®istry);
- mutex_unlock(&rcu_gp_lock);
+ mutex_unlock(&rcu_registry_lock);
}
void rcu_unregister_thread(void)
{
- mutex_lock(&rcu_gp_lock);
+ mutex_lock(&rcu_registry_lock);
+ assert(URCU_TLS(rcu_reader).registered);
+ URCU_TLS(rcu_reader).registered = 0;
cds_list_del(&URCU_TLS(rcu_reader).node);
- mutex_unlock(&rcu_gp_lock);
+ mutex_unlock(&rcu_registry_lock);
}
#ifdef RCU_MEMBARRIER
void rcu_init(void)
{
+ int ret;
+
if (init_done)
return;
init_done = 1;
- if (!membarrier(MEMBARRIER_EXPEDITED | MEMBARRIER_QUERY))
+ ret = membarrier(MEMBARRIER_CMD_QUERY, 0);
+ if (ret >= 0 && (ret & MEMBARRIER_CMD_SHARED)) {
rcu_has_sys_membarrier = 1;
+ }
}
#endif
* 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 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.
+ * holing the rcu_registry_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)
{
projects / urcu.git / blobdiff