On 02/29/2016 02:26 PM, Michal Hocko wrote:
From: Michal Hocko <mhocko@xxxxxxxx> coredump_wait waits for mmap_sem for write currently which can prevent oom_reaper to reclaim the oom victims address space asynchronously because that requires mmap_sem for read. This might happen if the oom victim is multi threaded and some thread(s) is holding mmap_sem for read (e.g. page fault) and it is stuck in the page allocator while other thread(s) reached coredump_wait already. This patch simply uses down_write_killable and bails out with EINTR if the lock got interrupted by the fatal signal. do_coredump will return right away and do_group_exit will take care to zap the whole thread group. Cc: Oleg Nesterov <oleg@xxxxxxxxxx> Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
--- fs/coredump.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/fs/coredump.c b/fs/coredump.c index 9ea87e9fdccf..6b8aa1629891 100644 --- a/fs/coredump.c +++ b/fs/coredump.c @@ -410,7 +410,9 @@ static int coredump_wait(int exit_code, struct core_state *core_state) core_state->dumper.task = tsk; core_state->dumper.next = NULL; - down_write(&mm->mmap_sem); + if (down_write_killable(&mm->mmap_sem)) + return -EINTR; + if (!mm->core_state) core_waiters = zap_threads(tsk, mm, core_state, exit_code); up_write(&mm->mmap_sem);
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