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author | Michal Hocko <mhocko@suse.com> | 2016-03-25 22:20:41 +0100 |
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committer | Linus Torvalds <torvalds@linux-foundation.org> | 2016-03-26 00:37:42 +0100 |
commit | e26796066fdf929cbba22dabb801808f986acdb9 (patch) | |
tree | ef8564918c72f9c8e79269077e723ac76a69dc73 /mm/oom_kill.c | |
parent | oom: make oom_reaper_list single linked (diff) | |
download | linux-e26796066fdf929cbba22dabb801808f986acdb9.tar.xz linux-e26796066fdf929cbba22dabb801808f986acdb9.zip |
oom: make oom_reaper freezable
After "oom: clear TIF_MEMDIE after oom_reaper managed to unmap the
address space" oom_reaper will call exit_oom_victim on the target task
after it is done. This might however race with the PM freezer:
CPU0 CPU1 CPU2
freeze_processes
try_to_freeze_tasks
# Allocation request
out_of_memory
oom_killer_disable
wake_oom_reaper(P1)
__oom_reap_task
exit_oom_victim(P1)
wait_event(oom_victims==0)
[...]
do_exit(P1)
perform IO/interfere with the freezer
which breaks the oom_killer_disable semantic. We no longer have a
guarantee that the oom victim won't interfere with the freezer because
it might be anywhere on the way to do_exit while the freezer thinks the
task has already terminated. It might trigger IO or touch devices which
are frozen already.
In order to close this race, make the oom_reaper thread freezable. This
will work because
a) already running oom_reaper will block freezer to enter the
quiescent state
b) wake_oom_reaper will not wake up the reaper after it has been
frozen
c) the only way to call exit_oom_victim after try_to_freeze_tasks
is from the oom victim's context when we know the further
interference shouldn't be possible
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: David Rientjes <rientjes@google.com>
Cc: Mel Gorman <mgorman@techsingularity.net>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/oom_kill.c')
-rw-r--r-- | mm/oom_kill.c | 2 |
1 files changed, 2 insertions, 0 deletions
diff --git a/mm/oom_kill.c b/mm/oom_kill.c index a49638f41e45..8cc55f0f0e5c 100644 --- a/mm/oom_kill.c +++ b/mm/oom_kill.c @@ -525,6 +525,8 @@ static void oom_reap_task(struct task_struct *tsk) static int oom_reaper(void *unused) { + set_freezable(); + while (true) { struct task_struct *tsk = NULL; |