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 <[email protected]> Acked-by: Oleg Nesterov <[email protected]> Acked-by: Vlastimil Babka <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
niw · May 24, 2016 · 4136c26 · 4136c26
1 parent 6904817
commit 4136c26
Showing 1 changed file with 3 additions and 1 deletion.
diff --git a/fs/coredump.c b/fs/coredump.c
@@ -413,7 +413,9 @@ 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);