diff options
authorRich Felker <>2020-07-06 18:46:57 -0400
committerRich Felker <>2020-07-06 18:46:57 -0400
commit52ee0dd6d5ccefcbf9b55748896c85801bfafd17 (patch)
parent7cc9496a18c3fa665c286b8be41d790c795e0171 (diff)
fix async-cancel-safety of pthread_cancel
the previous commit addressing async-signal-safety issues around pthread_kill did not fully fix pthread_cancel, which is also required (albeit rather irrationally) to be async-cancel-safe. without blocking implementation-internal signals, it's possible that, when async cancellation is enabled, a cancel signal sent by another thread interrupts pthread_kill while the killlock for a targeted thread is held. as a result, the calling thread will terminate due to cancellation without ever unlocking the targeted thread's killlock, and thus the targeted thread will be unable to exit.
1 files changed, 4 insertions, 1 deletions
diff --git a/src/thread/pthread_kill.c b/src/thread/pthread_kill.c
index 446254b6..79ddb209 100644
--- a/src/thread/pthread_kill.c
+++ b/src/thread/pthread_kill.c
@@ -5,7 +5,10 @@ int pthread_kill(pthread_t t, int sig)
int r;
sigset_t set;
- __block_app_sigs(&set);
+ /* Block not just app signals, but internal ones too, since
+ * pthread_kill is used to implement pthread_cancel, which
+ * must be async-cancel-safe. */
+ __block_all_sigs(&set);
r = t->tid ? -__syscall(SYS_tkill, t->tid, sig)
: (sig+0U >= _NSIG ? EINVAL : 0);