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[patch] testsuite: Fix a race by me - watchthreads-reorder.exp
- From: Jan Kratochvil <jan dot kratochvil at redhat dot com>
- To: gdb-patches at sourceware dot org
- Date: Thu, 17 Dec 2009 20:50:26 +0100
- Subject: [patch] testsuite: Fix a race by me - watchthreads-reorder.exp
Hi,
there is a bug explainable by man pthread_cond_signal:
The [...] pthread_cond_signal() functions shall have no effect if
there are no threads currently blocked on cond.
meaning a race for the testcase.
+FAIL: gdb.threads/watchthreads-reorder.exp: reorder1: continue a (timeout)
One can reproduce the race on CVS HEAD by:
# --- a/gdb/testsuite/gdb.threads/watchthreads-reorder.c
# +++ b/gdb/testsuite/gdb.threads/watchthreads-reorder.c
# @@ -89,6 +89,7 @@ thread1_func (void *unused)
# int i;
# volatile int rwatch_store;
#
# +sleep(1);
# thread1_tid = gettid ();
# i = pthread_cond_signal (&thread1_tid_cond);
# assert (i == 0);
# @@ -317,6 +318,7 @@ main (int argc, char **argv)
#
# if (thread1_tid == 0)
# {
# +sleep(2);
# i = pthread_cond_wait (&thread1_tid_cond, &thread1_tid_mutex);
# assert (i == 0);
#
Fixed; gdbstop_mutex got removed as it became redundant there.
Going to check it in as obvious in several days (code is by me + it is just
a testcase).
Sorry,
Jan
gdb/testsuite/
2009-12-17 Jan Kratochvil <jan.kratochvil@redhat.com>
* gdb.threads/watchthreads-reorder.c (gdbstop_mutex): Remove.
(thread1_func): Protect thread1_tid_cond by thread1_tid_mutex. Remove
gdbstop_mutex handling.
(thread2_func): Protect thread2_tid_cond by thread2_tid_mutex. Remove
gdbstop_mutex handling.
(main): Move thread1_tid_mutex and thread2_tid_mutex locks before
pthread_create. Remove gdbstop_mutex handling. New comment. Remove
pthread_cond_wait conditionalizations.
--- a/gdb/testsuite/gdb.threads/watchthreads-reorder.c
+++ b/gdb/testsuite/gdb.threads/watchthreads-reorder.c
@@ -34,8 +34,6 @@
otherwise. */
#define TIMEOUT (gettid () == getpid() ? 10 : 15)
-static pthread_mutex_t gdbstop_mutex = PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP;
-
static pid_t thread1_tid;
static pthread_cond_t thread1_tid_cond = PTHREAD_COND_INITIALIZER;
static pthread_mutex_t thread1_tid_mutex = PTHREAD_ERRORCHECK_MUTEX_INITIALIZER_NP;
@@ -90,12 +88,11 @@ thread1_func (void *unused)
volatile int rwatch_store;
thread1_tid = gettid ();
+
+ timed_mutex_lock (&thread1_tid_mutex);
i = pthread_cond_signal (&thread1_tid_cond);
assert (i == 0);
-
- /* Be sure GDB is already stopped before continuing. */
- timed_mutex_lock (&gdbstop_mutex);
- i = pthread_mutex_unlock (&gdbstop_mutex);
+ i = pthread_mutex_unlock (&thread1_tid_mutex);
assert (i == 0);
rwatch_store = thread1_rwatch;
@@ -115,12 +112,11 @@ thread2_func (void *unused)
volatile int rwatch_store;
thread2_tid = gettid ();
+
+ timed_mutex_lock (&thread2_tid_mutex);
i = pthread_cond_signal (&thread2_tid_cond);
assert (i == 0);
-
- /* Be sure GDB is already stopped before continuing. */
- timed_mutex_lock (&gdbstop_mutex);
- i = pthread_mutex_unlock (&gdbstop_mutex);
+ i = pthread_mutex_unlock (&thread2_tid_mutex);
assert (i == 0);
rwatch_store = thread2_rwatch;
@@ -267,7 +263,8 @@ main (int argc, char **argv)
setbuf (stdout, NULL);
- timed_mutex_lock (&gdbstop_mutex);
+ timed_mutex_lock (&thread1_tid_mutex);
+ timed_mutex_lock (&thread2_tid_mutex);
timed_mutex_lock (&terminate_mutex);
@@ -306,30 +303,21 @@ main (int argc, char **argv)
state_wait (tracer, "T (stopped)");
}
- timed_mutex_lock (&thread1_tid_mutex);
- timed_mutex_lock (&thread2_tid_mutex);
-
- /* Let the threads start. */
- i = pthread_mutex_unlock (&gdbstop_mutex);
- assert (i == 0);
+ /* Threads are now waiting at timed_mutex_lock (thread1_tid_mutex) and so
+ they could not trigger the watchpoints before GDB gets unstopped later.
+ Threads get resumed at pthread_cond_wait below. */
printf ("Waiting till the threads initialize their TIDs.\n");
- if (thread1_tid == 0)
- {
- i = pthread_cond_wait (&thread1_tid_cond, &thread1_tid_mutex);
- assert (i == 0);
+ i = pthread_cond_wait (&thread1_tid_cond, &thread1_tid_mutex);
+ assert (i == 0);
- assert (thread1_tid > 0);
- }
+ assert (thread1_tid > 0);
- if (thread2_tid == 0)
- {
- i = pthread_cond_wait (&thread2_tid_cond, &thread2_tid_mutex);
- assert (i == 0);
+ i = pthread_cond_wait (&thread2_tid_cond, &thread2_tid_mutex);
+ assert (i == 0);
- assert (thread2_tid > 0);
- }
+ assert (thread2_tid > 0);
printf ("Thread 1 TID = %lu, thread 2 TID = %lu, PID = %lu.\n",
(unsigned long) thread1_tid, (unsigned long) thread2_tid,