Skip to content

Fix a race condition in pthread_mutex_timedlock.c #12245

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Closed
wants to merge 3 commits into from
Closed

Fix a race condition in pthread_mutex_timedlock.c #12245

Changes from all commits
Commits
Show all changes
3 commits
Select commit Hold shift + click to select a range
361ff90
Fix a pthreads race condition
kripken Sep 17, 2020
bb08b54
shorter
kripken Sep 17, 2020
c959116
better
kripken Sep 17, 2020
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
14 changes: 13 additions & 1 deletion system/lib/libc/musl/src/thread/pthread_mutex_timedlock.c
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -20,7 +20,19 @@ int __pthread_mutex_timedlock(pthread_mutex_t *restrict m, const struct timespec
if ((m->_m_type&3) == PTHREAD_MUTEX_ERRORCHECK
&& (r&0x7fffffff) == __pthread_self()->tid)
return EDEADLK;

#ifdef __EMSCRIPTEN__
// If no time is given, do not sleep forever - there is a possible race
// condition here. We need to keep iterating in this loop, since _m_lock
// may be set to the value we want *just* before the __timedwait. __timedwait
// does not check if the value is what we want, it just checks for a wake on
// that address, so it would wait forever.
// Instead of picking some arbitrary time to wait, just keep busy-waiting.
if (!at) {
r = pthread_mutex_trylock(m);
if (r != EBUSY) return r;
}
continue;
#endif
a_inc(&m->_m_waiters);
t = r | 0x80000000;
a_cas(&m->_m_lock, r, t);
Expand Down