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| author | Kaarle Ritvanen <kaarle.ritvanen@datakunkku.fi> | 2018-09-18 10:03:27 +0300 |
|---|---|---|
| committer | Rich Felker <dalias@aerifal.cx> | 2018-09-18 11:43:49 -0400 |
| commit | 0db393d3a77bb9f300a356c6a5484fc2dddb161d (patch) | |
| tree | 16663af93aca5241a5a196a9a4b6805dc2fbf7e7 /src/misc | |
| parent | 1f6cbdb434114139081fe65a9bafe775e9ab6c41 (diff) | |
| download | musl-0db393d3a77bb9f300a356c6a5484fc2dddb161d.tar.gz musl-0db393d3a77bb9f300a356c6a5484fc2dddb161d.tar.bz2 musl-0db393d3a77bb9f300a356c6a5484fc2dddb161d.tar.xz musl-0db393d3a77bb9f300a356c6a5484fc2dddb161d.zip | |
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.
Diffstat (limited to 'src/misc')
0 files changed, 0 insertions, 0 deletions