https://bugs.kde.org/show_bug.cgi?id=502871
Bug ID: 502871
Summary: Make Helgrind "pthread_cond_{signal,broadcast}:
dubious: associated lock is not held by any thread"
optional
Classification: Developer tools
Product: valgrind
Version: 3.25 GIT
Platform: Compiled Sources
OS: Unspecified
Status: REPORTED
Severity: normal
Priority: NOR
Component: helgrind
Assignee: [email protected]
Reporter: [email protected]
Target Milestone: ---
On Illumos and Solaris I want to make this optional and off by default.
The Illumos man page for pthread_cond_broadcast says
The pthread_cond_signal() or pthread_cond_broadcast() functions may be
called by a thread whether or not it currently owns the mutex that
threads calling pthread_cond_wait() or pthread_cond_timedwait() have
associated with the condition variable during their waits; however, if
predictable scheduling behavior is required, then that mutex is locked
by the thread calling pthread_cond_signal() or
pthread_cond_broadcast().
Here is the Illumos implementation of pthread_barrier_wait:
int
pthread_barrier_wait(pthread_barrier_t *barrier)
{
mutex_t *mp = (mutex_t *)&barrier->__pthread_barrier_lock;
cond_t *cvp = (cond_t *)&barrier->__pthread_barrier_cond;
uint64_t cycle;
int cancel_state;
(void) mutex_lock(mp);
if (--barrier->__pthread_barrier_current == 0) {
barrier->__pthread_barrier_cycle++;
barrier->__pthread_barrier_current =
barrier->__pthread_barrier_count;
(void) mutex_unlock(mp);
(void) cond_broadcast(cvp);
return (PTHREAD_BARRIER_SERIAL_THREAD);
}
(void) pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &cancel_state);
cycle = barrier->__pthread_barrier_cycle;
do {
(void) cond_wait(cvp, mp);
} while (cycle == barrier->__pthread_barrier_cycle);
(void) pthread_setcancelstate(cancel_state, NULL);
(void) mutex_unlock(mp);
return (0);
}
The key thing there is
(void) mutex_unlock(mp);
(void) cond_broadcast(cvp);
That means that there is a "dubious associated lock" error every time that
pthread_barrier_wait fires due to the barrier count reaching zero.
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