* Copyright February 2009 - Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
*
* Distributed under GPLv2
+ *
+ * IBM's contributions to this file may be relicensed under LGPLv2 or later.
*/
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
#include <string.h>
+#include <errno.h>
+#include <poll.h>
#include "urcu.h"
struct reader_registry {
pthread_t tid;
long *urcu_active_readers;
+ char *need_mb;
};
#ifdef DEBUG_YIELD
#endif
static struct reader_registry *registry;
+static char __thread need_mb;
static int num_readers, alloc_readers;
-#ifndef DEBUG_FULL_MB
-static int sig_done;
-#endif
void internal_urcu_lock(void)
{
-#if 0
int ret;
- /* Mutex sleeping does not play well with busy-waiting loop. */
+
+#ifndef DISTRUST_SIGNALS_EXTREME
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();
+#else /* #ifndef DISTRUST_SIGNALS_EXTREME */
+ while ((ret = pthread_mutex_trylock(&urcu_mutex)) != 0) {
+ if (ret != EBUSY && ret != EINTR) {
+ printf("ret = %d, errno = %d\n", ret, errno);
+ perror("Error in pthread mutex lock");
+ exit(-1);
+ }
+ if (need_mb) {
+ smp_mb();
+ need_mb = 0;
+ smp_mb();
+ }
+ poll(NULL,0,10);
+ }
+#endif /* #else #ifndef DISTRUST_SIGNALS_EXTREME */
}
void internal_urcu_unlock(void)
}
#ifdef DEBUG_FULL_MB
-static void force_mb_single_thread(pthread_t tid)
+#ifdef HAS_INCOHERENT_CACHES
+static void force_mb_single_thread(struct reader_registry *index)
{
smp_mb();
}
+#endif /* #ifdef HAS_INCOHERENT_CACHES */
static void force_mb_all_threads(void)
{
smp_mb();
}
-#else
-
-static void force_mb_single_thread(pthread_t tid)
+#else /* #ifdef DEBUG_FULL_MB */
+#ifdef HAS_INCOHERENT_CACHES
+static void force_mb_single_thread(struct reader_registry *index)
{
assert(registry);
- 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);
+ *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 (LOAD_SHARED(sig_done) < 1)
- cpu_relax();
- smp_mb(); /* read sig_done before ending the barrier */
+ while (*index->need_mb) {
+ poll(NULL, 0, 1);
+ }
+ smp_mb(); /* read ->need_mb before ending the barrier */
}
+#endif /* #ifdef HAS_INCOHERENT_CACHES */
static void force_mb_all_threads(void)
{
*/
if (!registry)
return;
- 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 */
- for (index = registry; index < registry + num_readers; index++)
+ for (index = registry; index < registry + num_readers; index++) {
+ *index->need_mb = 1;
+ smp_mc(); /* write need_mb before sending the signal */
pthread_kill(index->tid, SIGURCU);
+ }
/*
* Wait for sighandler (and thus mb()) to execute on every thread.
- * BUSY-LOOP.
+ *
+ * Note that the pthread_kill() will never be executed on systems
+ * that correctly deliver signals in a timely manner. However, it
+ * is not uncommon for kernels to have bugs that can result in
+ * lost or unduly delayed signals.
+ *
+ * If you are seeing the below pthread_kill() executing much at
+ * all, we suggest testing the underlying kernel and filing the
+ * relevant bug report. For Linux kernels, we recommend getting
+ * the Linux Test Project (LTP).
*/
- while (LOAD_SHARED(sig_done) < num_readers)
- cpu_relax();
- smp_mb(); /* read sig_done before ending the barrier */
+ for (index = registry; index < registry + num_readers; index++) {
+ while (*index->need_mb) {
+ pthread_kill(index->tid, SIGURCU);
+ poll(NULL, 0, 1);
+ }
+ }
+ smp_mb(); /* read ->need_mb before ending the barrier */
}
-#endif
+#endif /* #else #ifdef DEBUG_FULL_MB */
void wait_for_quiescent_state(void)
{
* Wait for each thread urcu_active_readers count to become 0.
*/
for (index = registry; index < registry + num_readers; index++) {
+#ifndef HAS_INCOHERENT_CACHES
+ while (rcu_old_gp_ongoing(index->urcu_active_readers))
+ cpu_relax();
+#else /* #ifndef HAS_INCOHERENT_CACHES */
int wait_loops = 0;
/*
* BUSY-LOOP. Force the reader thread to commit its
*/
while (rcu_old_gp_ongoing(index->urcu_active_readers)) {
if (wait_loops++ == KICK_READER_LOOPS) {
- force_mb_single_thread(index->tid);
+ force_mb_single_thread(index);
wait_loops = 0;
} else {
cpu_relax();
}
}
+#endif /* #else #ifndef HAS_INCOHERENT_CACHES */
}
}
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++;
}
* executed on.
*/
smp_mb();
- atomic_inc(&sig_done);
+ need_mb = 0;
+ smp_mb();
}
void __attribute__((constructor)) urcu_init(void)
assert(act.sa_sigaction == sigurcu_handler);
free(registry);
}
-#endif
+#endif /* #ifndef DEBUG_FULL_MB */
projects / urcu.git / blobdiff