/* Do not #define _LGPL_SOURCE to ensure we can emit the wrapper symbols */
#include "urcu.h"
-#ifndef DEBUG_FULL_MB
+#ifndef URCU_MB
+static int init_done;
+
void __attribute__((constructor)) urcu_init(void);
void __attribute__((destructor)) urcu_exit(void);
#else
-static inline urcu_init(void)
+void urcu_init(void)
{
}
#endif
-int init_done;
+static pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER;
-pthread_mutex_t urcu_mutex = PTHREAD_MUTEX_INITIALIZER;
+int gp_futex;
/*
* Global grace period counter.
* Contains the current RCU_GP_CTR_BIT.
- * Also has a RCU_GP_CTR_BIT of 1, to accelerate the reader fast path.
+ * 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;
* Written to only by each individual reader. Read by both the reader and the
* writers.
*/
-long __thread urcu_active_readers;
-
-/* Thread IDs of registered readers */
-#define INIT_NUM_THREADS 4
-
-struct reader_registry {
- pthread_t tid;
- long *urcu_active_readers;
- char *need_mb;
-};
+struct urcu_reader __thread urcu_reader;
#ifdef DEBUG_YIELD
unsigned int yield_active;
unsigned int __thread rand_yield;
#endif
-static struct reader_registry *registry;
-static char __thread need_mb;
-static int num_readers, alloc_readers;
+static LIST_HEAD(registry);
-void internal_urcu_lock(void)
+static void internal_urcu_lock(void)
{
int ret;
perror("Error in pthread mutex lock");
exit(-1);
}
- if (need_mb) {
+ if (urcu_reader.need_mb) {
smp_mb();
- need_mb = 0;
+ urcu_reader.need_mb = 0;
smp_mb();
}
poll(NULL,0,10);
#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
}
-void internal_urcu_unlock(void)
+static void internal_urcu_unlock(void)
{
int ret;
STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr ^ RCU_GP_CTR_BIT);
}
-#ifdef DEBUG_FULL_MB
-#ifdef HAS_INCOHERENT_CACHES
-static void force_mb_single_thread(struct reader_registry *index)
+#ifdef URCU_MB
+#if 0 /* unused */
+static void force_mb_single_thread(struct urcu_reader *index)
{
smp_mb();
}
-#endif /* #ifdef HAS_INCOHERENT_CACHES */
+#endif //0
static void force_mb_all_threads(void)
{
smp_mb();
}
-#else /* #ifdef DEBUG_FULL_MB */
-#ifdef HAS_INCOHERENT_CACHES
-static void force_mb_single_thread(struct reader_registry *index)
+#else /* #ifdef URCU_MB */
+#if 0 /* unused */
+static void force_mb_single_thread(struct urcu_reader *index)
{
- assert(registry);
+ 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;
+ 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) {
+ while (index->need_mb) {
poll(NULL, 0, 1);
}
smp_mb(); /* read ->need_mb before ending the barrier */
}
-#endif /* #ifdef HAS_INCOHERENT_CACHES */
+#endif //0
static void force_mb_all_threads(void)
{
- struct reader_registry *index;
+ struct urcu_reader *index;
+
/*
* Ask for each threads to execute a smp_mb() so we can consider the
* compiler barriers around rcu read lock as real memory barriers.
*/
- if (!registry)
+ if (list_empty(®istry))
return;
/*
* pthread_kill has a smp_mb(). But beware, we assume it performs
* safe and don't assume anything : we use smp_mc() to make sure the
* cache flush is enforced.
*/
- for (index = registry; index < registry + num_readers; index++) {
- *index->need_mb = 1;
+ 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);
}
* relevant bug report. For Linux kernels, we recommend getting
* the Linux Test Project (LTP).
*/
- for (index = registry; index < registry + num_readers; index++) {
- while (*index->need_mb) {
+ list_for_each_entry(index, ®istry, head) {
+ while (index->need_mb) {
pthread_kill(index->tid, SIGURCU);
poll(NULL, 0, 1);
}
}
smp_mb(); /* read ->need_mb before ending the barrier */
}
-#endif /* #else #ifdef DEBUG_FULL_MB */
+#endif /* #else #ifdef URCU_MB */
+
+/*
+ * synchronize_rcu() waiting. Single thread.
+ */
+static void wait_gp(void)
+{
+ /* Read reader_gp before read futex */
+ force_mb_all_threads();
+ if (uatomic_read(&gp_futex) == -1)
+ futex(&gp_futex, FUTEX_WAIT, -1,
+ NULL, NULL, 0);
+}
void wait_for_quiescent_state(void)
{
- struct reader_registry *index;
+ LIST_HEAD(qsreaders);
+ int wait_loops = 0;
+ struct urcu_reader *index, *tmp;
- if (!registry)
+ if (list_empty(®istry))
return;
/*
- * Wait for each thread urcu_active_readers count to become 0.
+ * Wait for each thread urcu_reader.ctr count to become 0.
*/
- for (index = registry; index < registry + num_readers; index++) {
+ for (;;) {
+ wait_loops++;
+ if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
+ uatomic_dec(&gp_futex);
+ /* Write futex before read reader_gp */
+ force_mb_all_threads();
+ }
+
+ list_for_each_entry_safe(index, tmp, ®istry, head) {
+ if (!rcu_old_gp_ongoing(&index->ctr))
+ list_move(&index->head, &qsreaders);
+ }
+
#ifndef HAS_INCOHERENT_CACHES
- while (rcu_old_gp_ongoing(index->urcu_active_readers))
- cpu_relax();
+ if (list_empty(®istry)) {
+ if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
+ /* Read reader_gp before write futex */
+ force_mb_all_threads();
+ uatomic_set(&gp_futex, 0);
+ }
+ break;
+ } else {
+ if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS)
+ wait_gp();
+ else
+ cpu_relax();
+ }
#else /* #ifndef HAS_INCOHERENT_CACHES */
- int wait_loops = 0;
/*
* BUSY-LOOP. Force the reader thread to commit its
- * urcu_active_readers update to memory if we wait for too long.
+ * urcu_reader.ctr update to memory if we wait for too long.
*/
- while (rcu_old_gp_ongoing(index->urcu_active_readers)) {
- if (wait_loops++ == KICK_READER_LOOPS) {
- force_mb_single_thread(index);
+ if (list_empty(®istry)) {
+ if (wait_loops == RCU_QS_ACTIVE_ATTEMPTS) {
+ /* Read reader_gp before write futex */
+ force_mb_all_threads();
+ uatomic_set(&gp_futex, 0);
+ }
+ break;
+ } else {
+ switch (wait_loops) {
+ case RCU_QS_ACTIVE_ATTEMPTS:
+ wait_gp();
+ break; /* only escape switch */
+ case KICK_READER_LOOPS:
+ force_mb_all_threads();
wait_loops = 0;
- } else {
+ break; /* only escape switch */
+ default:
cpu_relax();
}
}
#endif /* #else #ifndef HAS_INCOHERENT_CACHES */
}
+ /* put back the reader list in the registry */
+ list_splice(&qsreaders, ®istry);
}
void synchronize_rcu(void)
void *rcu_assign_pointer_sym(void **p, void *v)
{
wmb();
- return STORE_SHARED(p, v);
+ return STORE_SHARED(*p, v);
}
void *rcu_xchg_pointer_sym(void **p, void *v)
{
wmb();
- return xchg(p, v);
+ 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)
return oldptr;
}
-static void rcu_add_reader(pthread_t id)
-{
- struct reader_registry *oldarray;
-
- if (!registry) {
- alloc_readers = INIT_NUM_THREADS;
- num_readers = 0;
- registry =
- malloc(sizeof(struct reader_registry) * alloc_readers);
- }
- if (alloc_readers < num_readers + 1) {
- oldarray = registry;
- registry = malloc(sizeof(struct reader_registry)
- * (alloc_readers << 1));
- memcpy(registry, oldarray,
- sizeof(struct reader_registry) * alloc_readers);
- alloc_readers <<= 1;
- free(oldarray);
- }
- registry[num_readers].tid = id;
- /* reference to the TLS of _this_ reader thread. */
- registry[num_readers].urcu_active_readers = &urcu_active_readers;
- registry[num_readers].need_mb = &need_mb;
- num_readers++;
-}
-
-/*
- * Never shrink (implementation limitation).
- * This is O(nb threads). Eventually use a hash table.
- */
-static void rcu_remove_reader(pthread_t id)
-{
- struct reader_registry *index;
-
- assert(registry != NULL);
- for (index = registry; index < registry + num_readers; index++) {
- if (pthread_equal(index->tid, id)) {
- memcpy(index, ®istry[num_readers - 1],
- sizeof(struct reader_registry));
- registry[num_readers - 1].tid = 0;
- registry[num_readers - 1].urcu_active_readers = NULL;
- num_readers--;
- return;
- }
- }
- /* Hrm not found, forgot to register ? */
- assert(0);
-}
-
void rcu_register_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 */
- rcu_add_reader(pthread_self());
+ list_add(&urcu_reader.head, ®istry);
internal_urcu_unlock();
}
void rcu_unregister_thread(void)
{
internal_urcu_lock();
- rcu_remove_reader(pthread_self());
+ list_del(&urcu_reader.head);
internal_urcu_unlock();
}
-#ifndef DEBUG_FULL_MB
+#ifndef URCU_MB
static void sigurcu_handler(int signo, siginfo_t *siginfo, void *context)
{
/*
* executed on.
*/
smp_mb();
- need_mb = 0;
+ urcu_reader.need_mb = 0;
smp_mb();
}
init_done = 1;
act.sa_sigaction = sigurcu_handler;
- act.sa_flags = SA_SIGINFO;
+ act.sa_flags = SA_SIGINFO | SA_RESTART;
sigemptyset(&act.sa_mask);
ret = sigaction(SIGURCU, &act, NULL);
if (ret) {
exit(-1);
}
assert(act.sa_sigaction == sigurcu_handler);
- free(registry);
+ assert(list_empty(®istry));
}
-#endif /* #ifndef DEBUG_FULL_MB */
+#endif /* #ifndef URCU_MB */
projects / urcu.git / blobdiff