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| author | Oleg Nesterov <oleg@redhat.com> | 2015-01-08 23:32:12 +0100 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2015-01-09 00:10:51 +0100 |
| commit | 3245d6acab981a2388ffb877c7ecc97e763c59d4 (patch) | |
| tree | 9fcebbce2ca688948665292358d22809f80140ba /mm/workingset.c | |
| parent | ocfs2: remove bogus check in dlm_process_recovery_data (diff) | |
| download | linux-3245d6acab981a2388ffb877c7ecc97e763c59d4.tar.xz linux-3245d6acab981a2388ffb877c7ecc97e763c59d4.zip | |
exit: fix race between wait_consider_task() and wait_task_zombie()
wait_consider_task() checks EXIT_ZOMBIE after EXIT_DEAD/EXIT_TRACE and
both checks can fail if we race with EXIT_ZOMBIE -> EXIT_DEAD/EXIT_TRACE
change in between, gcc needs to reload p->exit_state after
security_task_wait(). In this case ->notask_error will be wrongly
cleared and do_wait() can hang forever if it was the last eligible
child.
Many thanks to Arne who carefully investigated the problem.
Note: this bug is very old but it was pure theoretical until commit
b3ab03160dfa ("wait: completely ignore the EXIT_DEAD tasks"). Before
this commit "-O2" was probably enough to guarantee that compiler won't
read ->exit_state twice.
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Arne Goedeke <el@laramies.com>
Tested-by: Arne Goedeke <el@laramies.com>
Cc: <stable@vger.kernel.org> [3.15+]
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/workingset.c')
0 files changed, 0 insertions, 0 deletions