* 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.
+ * 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_data {
+struct reader_registry {
pthread_t tid;
long *urcu_active_readers;
};
unsigned int __thread rand_yield;
#endif
-static struct reader_data *reader_data;
+static struct reader_registry *registry;
static int num_readers, alloc_readers;
#ifndef DEBUG_FULL_MB
static int sig_done;
void internal_urcu_lock(void)
{
+#if 0
int ret;
+ /* Mutex sleeping does not play well with busy-waiting loop. */
ret = pthread_mutex_lock(&urcu_mutex);
if (ret) {
perror("Error in pthread mutex lock");
exit(-1);
}
+#endif
+ while (pthread_mutex_trylock(&urcu_mutex) != 0)
+ cpu_relax();
}
void internal_urcu_unlock(void)
*/
static void switch_next_urcu_qparity(void)
{
- urcu_gp_ctr ^= RCU_GP_CTR_BIT;
+ STORE_SHARED(urcu_gp_ctr, urcu_gp_ctr ^ RCU_GP_CTR_BIT);
}
#ifdef DEBUG_FULL_MB
static void force_mb_single_thread(pthread_t tid)
{
- assert(reader_data);
+ assert(registry);
sig_done = 0;
/*
* pthread_kill has a smp_mb(). But beware, we assume it performs
* Wait for sighandler (and thus mb()) to execute on every thread.
* BUSY-LOOP.
*/
- while (LOAD_REMOTE(sig_done) < 1)
+ while (LOAD_SHARED(sig_done) < 1)
cpu_relax();
smp_mb(); /* read sig_done before ending the barrier */
}
static void force_mb_all_threads(void)
{
- struct reader_data *index;
+ struct reader_registry *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 (!reader_data)
+ if (!registry)
return;
sig_done = 0;
/*
* smp_mb(); write sig_done before sending the signals
*/
smp_mc(); /* write sig_done before sending the signals */
- for (index = reader_data; index < reader_data + num_readers; index++)
+ for (index = registry; index < registry + num_readers; index++)
pthread_kill(index->tid, SIGURCU);
/*
* Wait for sighandler (and thus mb()) to execute on every thread.
* BUSY-LOOP.
*/
- while (LOAD_REMOTE(sig_done) < num_readers)
+ while (LOAD_SHARED(sig_done) < num_readers)
cpu_relax();
smp_mb(); /* read sig_done before ending the barrier */
}
void wait_for_quiescent_state(void)
{
- struct reader_data *index;
+ struct reader_registry *index;
- if (!reader_data)
+ if (!registry)
return;
/*
* Wait for each thread urcu_active_readers count to become 0.
*/
- for (index = reader_data; index < reader_data + num_readers; index++) {
+ for (index = registry; index < registry + num_readers; index++) {
int wait_loops = 0;
/*
* BUSY-LOOP. Force the reader thread to commit its
if (wait_loops++ == KICK_READER_LOOPS) {
force_mb_single_thread(index->tid);
wait_loops = 0;
+ } else {
+ cpu_relax();
}
}
}
* 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.
*/
- smp_mc();
/*
* Wait for previous parity to be empty of readers.
* 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.
*/
- smp_mc();
switch_next_urcu_qparity(); /* 1 -> 0 */
* 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.
*/
- smp_mc();
/*
* Wait for previous parity to be empty of readers.
void urcu_add_reader(pthread_t id)
{
- struct reader_data *oldarray;
+ struct reader_registry *oldarray;
- if (!reader_data) {
+ if (!registry) {
alloc_readers = INIT_NUM_THREADS;
num_readers = 0;
- reader_data =
- malloc(sizeof(struct reader_data) * alloc_readers);
+ registry =
+ malloc(sizeof(struct reader_registry) * alloc_readers);
}
if (alloc_readers < num_readers + 1) {
- oldarray = reader_data;
- reader_data = malloc(sizeof(struct reader_data)
+ oldarray = registry;
+ registry = malloc(sizeof(struct reader_registry)
* (alloc_readers << 1));
- memcpy(reader_data, oldarray,
- sizeof(struct reader_data) * alloc_readers);
+ memcpy(registry, oldarray,
+ sizeof(struct reader_registry) * alloc_readers);
alloc_readers <<= 1;
free(oldarray);
}
- reader_data[num_readers].tid = id;
+ registry[num_readers].tid = id;
/* reference to the TLS of _this_ reader thread. */
- reader_data[num_readers].urcu_active_readers = &urcu_active_readers;
+ registry[num_readers].urcu_active_readers = &urcu_active_readers;
num_readers++;
}
*/
void urcu_remove_reader(pthread_t id)
{
- struct reader_data *index;
+ struct reader_registry *index;
- assert(reader_data != NULL);
- for (index = reader_data; index < reader_data + num_readers; index++) {
+ assert(registry != NULL);
+ for (index = registry; index < registry + num_readers; index++) {
if (pthread_equal(index->tid, id)) {
- memcpy(index, &reader_data[num_readers - 1],
- sizeof(struct reader_data));
- reader_data[num_readers - 1].tid = 0;
- reader_data[num_readers - 1].urcu_active_readers = NULL;
+ 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;
}
exit(-1);
}
assert(act.sa_sigaction == sigurcu_handler);
- free(reader_data);
+ free(registry);
}
#endif
projects / urcu.git / blobdiff