}
#endif
-/* Sleep delay in us */
-#define RCU_SLEEP_DELAY 1000
+/* Sleep delay in ms */
+#define RCU_SLEEP_DELAY_MS 10
#define INIT_NR_THREADS 8
#define ARENA_INIT_ALLOC \
sizeof(struct registry_chunk) \
*/
#define RCU_QS_ACTIVE_ATTEMPTS 100
+static
+int rcu_bp_refcount;
+
static
void __attribute__((constructor)) rcu_bp_init(void);
static
-void __attribute__((destructor)) rcu_bp_exit(void);
+void __attribute__((destructor)) _rcu_bp_exit(void);
+/*
+ * 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;
static pthread_mutex_t init_lock = PTHREAD_MUTEX_INITIALIZER;
static int initialized;
urcu_die(ret);
}
+/*
+ * Always called with rcu_registry lock held. Releases this lock between
+ * iterations and grabs it again. Holds the lock when it returns.
+ */
void update_counter_and_wait(void)
{
CDS_LIST_HEAD(qsreaders);
- int wait_loops = 0;
+ unsigned int wait_loops = 0;
struct rcu_reader *index, *tmp;
/* Switch parity: 0 -> 1, 1 -> 0 */
* Wait for each thread rcu_reader.ctr count to become 0.
*/
for (;;) {
- wait_loops++;
+ if (wait_loops < RCU_QS_ACTIVE_ATTEMPTS)
+ wait_loops++;
+
cds_list_for_each_entry_safe(index, tmp, ®istry, node) {
if (!rcu_old_gp_ongoing(&index->ctr))
cds_list_move(&index->node, &qsreaders);
if (cds_list_empty(®istry)) {
break;
} else {
- if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS)
- usleep(RCU_SLEEP_DELAY);
+ /* Temporarily unlock the registry lock. */
+ mutex_unlock(&rcu_registry_lock);
+ if (wait_loops >= RCU_QS_ACTIVE_ATTEMPTS)
+ (void) poll(NULL, 0, RCU_SLEEP_DELAY_MS);
else
caa_cpu_relax();
+ /* Re-lock the registry lock before the next loop. */
+ mutex_lock(&rcu_registry_lock);
}
}
/* put back the reader list in the registry */
assert(!ret);
mutex_lock(&rcu_gp_lock);
+ mutex_lock(&rcu_registry_lock);
if (cds_list_empty(®istry))
goto out;
/*
* Wait for previous parity to be empty of readers.
+ * update_counter_and_wait() can release and grab again
+ * rcu_registry_lock interally.
*/
update_counter_and_wait(); /* 0 -> 1, wait readers in parity 0 */
/*
* Wait for previous parity to be empty of readers.
+ * update_counter_and_wait() can release and grab again
+ * rcu_registry_lock interally.
*/
update_counter_and_wait(); /* 1 -> 0, wait readers in parity 1 */
*/
cmm_smp_mb();
out:
+ mutex_unlock(&rcu_registry_lock);
mutex_unlock(&rcu_gp_lock);
ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
assert(!ret);
/* Called with signals off and mutex locked */
static
-void remove_thread(void)
+void remove_thread(struct rcu_reader *rcu_reader_reg)
{
- struct rcu_reader *rcu_reader_reg;
-
- rcu_reader_reg = URCU_TLS(rcu_reader);
cleanup_thread(find_chunk(rcu_reader_reg), rcu_reader_reg);
URCU_TLS(rcu_reader) = NULL;
}
*/
rcu_bp_init();
- mutex_lock(&rcu_gp_lock);
+ mutex_lock(&rcu_registry_lock);
add_thread();
- mutex_unlock(&rcu_gp_lock);
+ mutex_unlock(&rcu_registry_lock);
end:
ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
if (ret)
/* Disable signals, take mutex, remove from registry */
static
-void rcu_bp_unregister(void)
+void rcu_bp_unregister(struct rcu_reader *rcu_reader_reg)
{
sigset_t newmask, oldmask;
int ret;
if (ret)
abort();
- mutex_lock(&rcu_gp_lock);
- remove_thread();
- mutex_unlock(&rcu_gp_lock);
+ mutex_lock(&rcu_registry_lock);
+ remove_thread(rcu_reader_reg);
+ mutex_unlock(&rcu_registry_lock);
ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
if (ret)
abort();
+ _rcu_bp_exit();
}
/*
static
void urcu_bp_thread_exit_notifier(void *rcu_key)
{
- assert(rcu_key == URCU_TLS(rcu_reader));
- rcu_bp_unregister();
+ rcu_bp_unregister(rcu_key);
}
static
void rcu_bp_init(void)
{
mutex_lock(&init_lock);
- if (!initialized) {
+ if (!rcu_bp_refcount++) {
int ret;
ret = pthread_key_create(&urcu_bp_key,
}
static
-void rcu_bp_exit(void)
+void _rcu_bp_exit(void)
{
- struct registry_chunk *chunk, *tmp;
- int ret;
+ mutex_lock(&init_lock);
+ if (!--rcu_bp_refcount) {
+ struct registry_chunk *chunk, *tmp;
+ int ret;
- cds_list_for_each_entry_safe(chunk, tmp,
- ®istry_arena.chunk_list, node) {
- munmap(chunk, chunk->data_len + sizeof(struct registry_chunk));
+ cds_list_for_each_entry_safe(chunk, tmp,
+ ®istry_arena.chunk_list, node) {
+ munmap(chunk, chunk->data_len
+ + sizeof(struct registry_chunk));
+ }
+ ret = pthread_key_delete(urcu_bp_key);
+ if (ret)
+ abort();
}
- ret = pthread_key_delete(urcu_bp_key);
- if (ret)
- abort();
+ mutex_unlock(&init_lock);
+}
+
+/*
+ * Keep ABI compability within stable versions. This has never been
+ * exposed through a header, but needs to stay in the .so until the
+ * soname is bumped.
+ */
+void rcu_bp_exit(void)
+{
}
/*
- * Holding the rcu_gp_lock across fork will make sure we fork() don't race with
- * a concurrent thread executing with this same lock held. This ensures that the
- * registry is in a coherent state in the child.
+ * Holding the rcu_gp_lock and rcu_registry_lock across fork will make
+ * sure we fork() don't race with a concurrent thread executing with
+ * any of those locks held. This ensures that the registry and data
+ * protected by rcu_gp_lock are in a coherent state in the child.
*/
void rcu_bp_before_fork(void)
{
ret = pthread_sigmask(SIG_BLOCK, &newmask, &oldmask);
assert(!ret);
mutex_lock(&rcu_gp_lock);
+ mutex_lock(&rcu_registry_lock);
saved_fork_signal_mask = oldmask;
}
int ret;
oldmask = saved_fork_signal_mask;
+ mutex_unlock(&rcu_registry_lock);
mutex_unlock(&rcu_gp_lock);
ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
assert(!ret);
/*
* Prune all entries from registry except our own thread. Fits the Linux
- * fork behavior. Called with rcu_gp_lock held.
+ * fork behavior. Called with rcu_gp_lock and rcu_registry_lock held.
*/
static
void urcu_bp_prune_registry(void)
urcu_bp_prune_registry();
oldmask = saved_fork_signal_mask;
+ mutex_unlock(&rcu_registry_lock);
mutex_unlock(&rcu_gp_lock);
ret = pthread_sigmask(SIG_SETMASK, &oldmask, NULL);
assert(!ret);
projects / userspace-rcu.git / blobdiff