}
#ifdef DEBUG_FULL_MB
+static void force_mb_single_thread(pthread_t tid)
+{
+ smp_mb();
+}
+
static void force_mb_all_threads(void)
{
smp_mb();
}
#else
+
+static void force_mb_single_thread(pthread_t tid)
+{
+ assert(reader_data);
+ sig_done = 0;
+ /*
+ * 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.
+ * smp_mb(); write sig_done before sending the signals
+ */
+ smp_mc(); /* write sig_done before sending the signals */
+ pthread_kill(tid, SIGURCU);
+ /*
+ * Wait for sighandler (and thus mb()) to execute on every thread.
+ * BUSY-LOOP.
+ */
+ while (LOAD_REMOTE(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;
*/
if (!reader_data)
return;
- debug_yield_write();
sig_done = 0;
- debug_yield_write();
- smp_mb(); /* write sig_done before sending the signals */
- debug_yield_write();
- for (index = reader_data; index < reader_data + num_readers; index++) {
+ /*
+ * 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.
+ * 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++)
pthread_kill(index->tid, SIGURCU);
- debug_yield_write();
- }
/*
* Wait for sighandler (and thus mb()) to execute on every thread.
* BUSY-LOOP.
*/
- while (sig_done < num_readers)
- barrier();
- debug_yield_write();
+ while (LOAD_REMOTE(sig_done) < num_readers)
+ cpu_relax();
smp_mb(); /* read sig_done before ending the barrier */
- debug_yield_write();
}
#endif
if (!reader_data)
return;
- /* Wait for each thread urcu_active_readers count to become 0.
+ /*
+ * Wait for each thread urcu_active_readers count to become 0.
*/
for (index = reader_data; index < reader_data + num_readers; index++) {
+ int wait_loops = 0;
/*
- * BUSY-LOOP.
+ * BUSY-LOOP. Force the reader thread to commit its
+ * urcu_active_readers update to memory if we wait for too long.
*/
- while (rcu_old_gp_ongoing(index->urcu_active_readers))
- barrier();
+ while (rcu_old_gp_ongoing(index->urcu_active_readers)) {
+ if (wait_loops++ == KICK_READER_LOOPS) {
+ force_mb_single_thread(index->tid);
+ wait_loops = 0;
+ } else {
+ cpu_relax();
+ }
+ }
}
}
void synchronize_rcu(void)
{
+ internal_urcu_lock();
+
/* All threads should read qparity before accessing data structure
- * where new ptr points to. */
+ * where new ptr points to. Must be done within internal_urcu_lock
+ * because it iterates on reader threads.*/
/* Write new ptr before changing the qparity */
force_mb_all_threads();
- debug_yield_write();
-
- internal_urcu_lock();
- debug_yield_write();
switch_next_urcu_qparity(); /* 0 -> 1 */
- debug_yield_write();
/*
* Must commit qparity update to memory before waiting for parity
* waiting forever while new readers are always accessing data (no
* progress).
*/
- smp_mb();
+ smp_mc();
/*
* Wait for previous parity to be empty of readers.
*/
wait_for_quiescent_state(); /* Wait readers in parity 0 */
- debug_yield_write();
/*
* Must finish waiting for quiescent state for parity 0 before
* the writer waiting forever while new readers are always accessing
* data (no progress).
*/
- smp_mb();
+ smp_mc();
switch_next_urcu_qparity(); /* 1 -> 0 */
- debug_yield_write();
/*
* Must commit qparity update to memory before waiting for parity
* waiting forever while new readers are always accessing data (no
* progress).
*/
- smp_mb();
+ smp_mc();
/*
* Wait for previous parity to be empty of readers.
*/
wait_for_quiescent_state(); /* Wait readers in parity 1 */
- debug_yield_write();
-
- internal_urcu_unlock();
- debug_yield_write();
- /* All threads should finish using the data referred to by old ptr
- * before decrementing their urcu_active_readers count */
/* Finish waiting for reader threads before letting the old ptr being
- * freed. */
+ * freed. Must be done within internal_urcu_lock because it iterates on
+ * reader threads. */
force_mb_all_threads();
- debug_yield_write();
+
+ internal_urcu_unlock();
}
void urcu_add_reader(pthread_t id)
#ifndef DEBUG_FULL_MB
void sigurcu_handler(int signo, siginfo_t *siginfo, void *context)
{
+ /*
+ * Executing this smp_mb() is the only purpose of this signal handler.
+ * It punctually promotes barrier() into smp_mb() on every thread it is
+ * executed on.
+ */
smp_mb();
atomic_inc(&sig_done);
}
projects / urcu.git / blobdiff