Re: [PATCH 11/18] coredump: make coredump_wait wait for mma_sem for write killable

From: Vlastimil Babka
Date: Fri Mar 11 2016 - 06:54:34 EST

On 03/11/2016 12:32 PM, Vlastimil Babka wrote:
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

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>

Forgot to point out typo in Subject which makes it hard to grep for mmap_sem