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authornormal <normal@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>2018-10-31 02:31:15 (GMT)
committernormal <normal@b2dd03c8-39d4-4d8f-98ff-823fe69b080e>2018-10-31 02:31:15 (GMT)
commit89aaf7db9eecc578491809ea145190816c30f4c5 (patch)
tree838eb4e29b889f48799d1687517fac55801ec848 /thread_pthread.c
parentce9911c4831cf09a7c35c04a7cc65ac24bbedec2 (diff)
thread_pthread.c (ubf_select): avoid deadlock on contention
vm->gvl.lock can be held by another thread, we must not wait on it when called by the MJIT worker thread when it migrates work to another thread. ubf_select is designed to do retrying anyways, so it has no obligation to wake up a timer thread. cf. http://ci.rvm.jp/results/trunk-mjit-wait@silicon-docker/1437880 git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65465 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
Diffstat (limited to 'thread_pthread.c')
-rw-r--r--thread_pthread.c14
1 files changed, 10 insertions, 4 deletions
diff --git a/thread_pthread.c b/thread_pthread.c
index a8bb4c7..97d6eaf 100644
--- a/thread_pthread.c
+++ b/thread_pthread.c
@@ -1342,11 +1342,17 @@ ubf_select(void *ptr)
* in unblock_function_clear.
*/
if (cur != vm->gvl.timer && cur != sigwait_th) {
- rb_native_mutex_lock(&vm->gvl.lock);
- if (!vm->gvl.timer) {
- rb_thread_wakeup_timer_thread(-1);
+ /*
+ * Double-checked locking above was to prevent nested locking
+ * by the SAME thread. We use trylock here to prevent deadlocks
+ * between DIFFERENT threads
+ */
+ if (native_mutex_trylock(&vm->gvl.lock) == 0) {
+ if (!vm->gvl.timer) {
+ rb_thread_wakeup_timer_thread(-1);
+ }
+ rb_native_mutex_unlock(&vm->gvl.lock);
}
- rb_native_mutex_unlock(&vm->gvl.lock);
}
ubf_wakeup_thread(th);