aboutsummaryrefslogtreecommitdiff
path: root/linuxthreads/mutex.c
diff options
context:
space:
mode:
authorUlrich Drepper <drepper@redhat.com>2000-05-08 00:03:03 +0000
committerUlrich Drepper <drepper@redhat.com>2000-05-08 00:03:03 +0000
commit93414bb97c8d4af09fbc6ed493e5c904f27a5173 (patch)
treeacc768bf3ed48a4cc8df3e31b97e63c42d5b13a3 /linuxthreads/mutex.c
parent639c6286de5391c9accf0ecb9f944efe7ed980b8 (diff)
downloadglibc-93414bb97c8d4af09fbc6ed493e5c904f27a5173.zip
glibc-93414bb97c8d4af09fbc6ed493e5c904f27a5173.tar.gz
glibc-93414bb97c8d4af09fbc6ed493e5c904f27a5173.tar.bz2
Update.
2000-05-07 H.J. Lu <hjl@gnu.org> * csu/initfini.c: Moved to .... * sysdeps/generic/initfini.c: ...here. * csu/Makefile (initfini.c): Set vpath to $(full_config_sysdirs).
Diffstat (limited to 'linuxthreads/mutex.c')
-rw-r--r--linuxthreads/mutex.c38
1 files changed, 32 insertions, 6 deletions
diff --git a/linuxthreads/mutex.c b/linuxthreads/mutex.c
index 4d9019e..a42167c 100644
--- a/linuxthreads/mutex.c
+++ b/linuxthreads/mutex.c
@@ -17,6 +17,7 @@
#include <errno.h>
#include <sched.h>
#include <stddef.h>
+#include <limits.h>
#include "pthread.h"
#include "internals.h"
#include "spinlock.h"
@@ -170,6 +171,7 @@ weak_alias (__pthread_mutexattr_getkind_np, pthread_mutexattr_getkind_np)
static pthread_mutex_t once_masterlock = PTHREAD_MUTEX_INITIALIZER;
static pthread_cond_t once_finished = PTHREAD_COND_INITIALIZER;
+static int fork_generation = 0; /* Child process increments this after fork. */
enum { NEVER = 0, IN_PROGRESS = 1, DONE = 2 };
@@ -199,14 +201,20 @@ int __pthread_once(pthread_once_t * once_control, void (*init_routine)(void))
state_changed = 0;
pthread_mutex_lock(&once_masterlock);
+
+ /* If this object was left in an IN_PROGRESS state in a parent
+ process (indicated by stale generation field), reset it to NEVER. */
+ if ((*once_control & 3) == IN_PROGRESS && (*once_control & ~3) != fork_generation)
+ *once_control = NEVER;
+
/* If init_routine is being called from another routine, wait until
it completes. */
- while (*once_control == IN_PROGRESS) {
+ while ((*once_control & 3) == IN_PROGRESS) {
pthread_cond_wait(&once_finished, &once_masterlock);
}
/* Here *once_control is stable and either NEVER or DONE. */
if (*once_control == NEVER) {
- *once_control = IN_PROGRESS;
+ *once_control = IN_PROGRESS | fork_generation;
pthread_mutex_unlock(&once_masterlock);
pthread_cleanup_push(pthread_once_cancelhandler, once_control);
init_routine();
@@ -225,13 +233,31 @@ int __pthread_once(pthread_once_t * once_control, void (*init_routine)(void))
strong_alias (__pthread_once, pthread_once)
/*
- * This is called in the child process after a fork to make
- * sure that the global mutex pthread_once is not held,
- * and that the condition variable is reset to an initial state.
+ * Handle the state of the pthread_once mechanism across forks. The
+ * once_masterlock is acquired in the parent process prior to a fork to ensure
+ * that no thread is in the critical region protected by the lock. After the
+ * fork, the lock is released. In the child, the lock and the condition
+ * variable are simply reset. The child also increments its generation
+ * counter which lets pthread_once calls detect stale IN_PROGRESS states
+ * and reset them back to NEVER.
*/
-void __pthread_reset_pthread_once(void)
+void __pthread_once_fork_prepare(void)
+{
+ pthread_mutex_lock(&once_masterlock);
+}
+
+void __pthread_once_fork_parent(void)
+{
+ pthread_mutex_unlock(&once_masterlock);
+}
+
+void __pthread_once_fork_child(void)
{
pthread_mutex_init(&once_masterlock, NULL);
pthread_cond_init(&once_finished, NULL);
+ if (fork_generation <= INT_MAX - 4)
+ fork_generation += 4; /* leave least significant two bits zero */
+ else
+ fork_generation = 0;
}