From 4ec5ffc198fcdcbea2dbca81a337900ac33b1fa7 Mon Sep 17 00:00:00 2001 From: Corinna Vinschen Date: Fri, 8 Mar 2019 12:51:10 +0100 Subject: Cygwin: posix timers: fix a deadlock Canceling the timer thread runs under lock. The thread uses the same lock to guard its timer_tracker struct access. If the timing is bad, timer_settime or timer_delete grab the lock at the same time, the timer expires. In the end, cancel waits for the thread sync while the thread waits for ther lock to be released. Fix this by not waiting for the thread sync under lock. Signed-off-by: Corinna Vinschen --- winsup/cygwin/posix_timer.cc | 2 ++ winsup/cygwin/release/3.0.3 | 3 +++ 2 files changed, 5 insertions(+) diff --git a/winsup/cygwin/posix_timer.cc b/winsup/cygwin/posix_timer.cc index a140b00e9..c0d548fe9 100644 --- a/winsup/cygwin/posix_timer.cc +++ b/winsup/cygwin/posix_timer.cc @@ -31,7 +31,9 @@ timer_tracker::cancel () SetEvent (cancel_evt); if (sync_thr) { + ReleaseSRWLockExclusive (&srwlock); res = WaitForSingleObject (sync_thr, INFINITE); + AcquireSRWLockExclusive (&srwlock); if (res != WAIT_OBJECT_0) debug_printf ("WFSO returned unexpected value %u, %E", res); } diff --git a/winsup/cygwin/release/3.0.3 b/winsup/cygwin/release/3.0.3 index 66ae63943..b8c89cbe9 100644 --- a/winsup/cygwin/release/3.0.3 +++ b/winsup/cygwin/release/3.0.3 @@ -11,3 +11,6 @@ Bug Fixes - Fix a resource leak in posix timers. Addresses: https://cygwin.com/ml/cygwin/2019-03/msg00120.html + +- Fix a deadlock in posix timers + Addresses: https://cygwin.com/ml/cygwin/2019-03/msg00158.html -- cgit v1.2.3