+++ /dev/null
-From 0db393d3a77bb9f300a356c6a5484fc2dddb161d Mon Sep 17 00:00:00 2001
-From: Kaarle Ritvanen <kaarle.ritvanen@datakunkku.fi>
-Date: Tue, 18 Sep 2018 10:03:27 +0300
-Subject: [PATCH] fix race condition in file locking
-
-The condition occurs when
-- thread #1 is holding the lock
-- thread #2 is waiting for it on __futexwait
-- thread #1 is about to release the lock and performs a_swap
-- thread #3 enters the __lockfile function and manages to grab the lock
- before thread #1 calls __wake, resetting the MAYBE_WAITERS flag
-- thread #1 calls __wake
-- thread #2 wakes up but goes again to __futexwait as the lock is
- held by thread #3
-- thread #3 releases the lock but does not call __wake as the
- MAYBE_WAITERS flag is not set
-
-This condition results in thread #2 not being woken up. This patch fixes
-the problem by making the woken up thread ensure that the flag is
-properly set before going to sleep again.
-
-Mainainer's note: This fixes a regression introduced in commit
-c21f750727515602a9e84f2a190ee8a0a2aeb2a1.
-Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
----
- src/stdio/__lockfile.c | 12 ++++++------
- 1 file changed, 6 insertions(+), 6 deletions(-)
-
-diff --git a/src/stdio/__lockfile.c b/src/stdio/__lockfile.c
-index 2ff75d8a..0dcb2a42 100644
---- a/src/stdio/__lockfile.c
-+++ b/src/stdio/__lockfile.c
-@@ -8,13 +8,13 @@ int __lockfile(FILE *f)
- int owner = f->lock, tid = __pthread_self()->tid;
- if ((owner & ~MAYBE_WAITERS) == tid)
- return 0;
-- for (;;) {
-- owner = a_cas(&f->lock, 0, tid);
-- if (!owner) return 1;
-- if (a_cas(&f->lock, owner, owner|MAYBE_WAITERS)==owner) break;
-+ owner = a_cas(&f->lock, 0, tid);
-+ if (!owner) return 1;
-+ while ((owner = a_cas(&f->lock, 0, tid|MAYBE_WAITERS))) {
-+ if ((owner & MAYBE_WAITERS) ||
-+ a_cas(&f->lock, owner, owner|MAYBE_WAITERS)==owner)
-+ __futexwait(&f->lock, owner|MAYBE_WAITERS, 1);
- }
-- while ((owner = a_cas(&f->lock, 0, tid|MAYBE_WAITERS)))
-- __futexwait(&f->lock, owner, 1);
- return 1;
- }
-
---
-2.14.4
-