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authorUlrich Drepper <drepper@redhat.com>1998-12-13 18:02:57 +0000
committerUlrich Drepper <drepper@redhat.com>1998-12-13 18:02:57 +0000
commite3743e2ffdef8246aff171309aa09b65a7ccebd8 (patch)
treec0fce1a50c576c4b3052e97c47161d302eac4a02
parent763babf874f0ea2b712dc688ba2c088d2378e5b6 (diff)
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Update.
1998-12-13 Ulrich Drepper <drepper@cygnus.com> * Examples/ex3.c: Wait until all threads are started before searching for the number to avoid race condition on very fast systems.
-rw-r--r--linuxthreads/ChangeLog6
-rw-r--r--linuxthreads/Examples/ex3.c16
2 files changed, 19 insertions, 3 deletions
diff --git a/linuxthreads/ChangeLog b/linuxthreads/ChangeLog
index a6913e9..a5d82a4 100644
--- a/linuxthreads/ChangeLog
+++ b/linuxthreads/ChangeLog
@@ -1,3 +1,9 @@
+1998-12-13 Ulrich Drepper <drepper@cygnus.com>
+
+ * Examples/ex3.c: Wait until all threads are started before
+ searching for the number to avoid race condition on very fast
+ systems.
+
1998-12-08 Andreas Jaeger <aj@arthur.rhein-neckar.de>
* sysdeps/pthread/pthread.h: Remove __pthread_setcanceltype
diff --git a/linuxthreads/Examples/ex3.c b/linuxthreads/Examples/ex3.c
index 7557cc7..8005200 100644
--- a/linuxthreads/Examples/ex3.c
+++ b/linuxthreads/Examples/ex3.c
@@ -19,6 +19,7 @@ void print_it(void *);
pthread_t threads[NUM_THREADS];
pthread_mutex_t lock;
int tries;
+volatile int started;
int main(int argc, char ** argv)
{
@@ -33,8 +34,8 @@ int main(int argc, char ** argv)
pthread_mutex_init(&lock, NULL);
/* Create the searching threads */
- for (i=0; i<NUM_THREADS; i++)
- pthread_create(&threads[i], NULL, search, (void *)pid);
+ for (started=0; started<NUM_THREADS; started++)
+ pthread_create(&threads[started], NULL, search, (void *)pid);
/* Wait for (join) all the searching threads */
for (i=0; i<NUM_THREADS; i++)
@@ -74,7 +75,13 @@ void *search(void *arg)
/* use the thread ID to set the seed for the random number generator */
/* Since srand and rand are not thread-safe, serialize with lock */
- pthread_mutex_lock(&lock);
+
+ /* Try to lock the mutex lock --
+ if locked, check to see if the thread has been cancelled
+ if not locked then continue */
+ while (pthread_mutex_trylock(&lock) == EBUSY)
+ pthread_testcancel();
+
srand((int)tid);
i = rand() & 0xFFFFFF;
pthread_mutex_unlock(&lock);
@@ -87,6 +94,9 @@ void *search(void *arg)
pthread_setcancelstate(PTHREAD_CANCEL_ENABLE, NULL);
pthread_setcanceltype(PTHREAD_CANCEL_DEFERRED, NULL);
+ while (started < NUM_THREADS)
+ sched_yield ();
+
/* Push the cleanup routine (print_it) onto the thread
cleanup stack. This routine will be called when the
thread is cancelled. Also note that the pthread_cleanup_push