coredump: make coredump_wait wait for mmap_sem for write killable
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.
Signed-off-by: Michal Hocko <mhocko@suse.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/coredump.c b/fs/coredump.c
index 492c2db..38a7ab8 100644
--- a/fs/coredump.c
+++ b/fs/coredump.c
@@ -413,7 +413,9 @@
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);