[PATCH 15/18] uprobes: wait for mmap_sem for write killable

From: Michal Hocko
Date: Mon Feb 29 2016 - 08:27:55 EST

From: Michal Hocko <mhocko@xxxxxxxx>

xol_add_vma needs mmap_sem for write. If the waiting task gets killed by
the oom killer it would block oom_reaper from asynchronous address space
reclaim and reduce the chances of timely OOM resolving. Wait for the
lock in the killable mode and return with EINTR if the task got killed
while waiting.

Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
kernel/events/uprobes.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c
index 8eef5f55d3f0..a79315d0f711 100644
--- a/kernel/events/uprobes.c
+++ b/kernel/events/uprobes.c
@@ -1130,7 +1130,9 @@ static int xol_add_vma(struct mm_struct *mm, struct xol_area *area)
struct vm_area_struct *vma;
int ret;

- down_write(&mm->mmap_sem);
+ if (down_write_killable(&mm->mmap_sem))
+ return -EINTR;
if (mm->uprobes_state.xol_area) {
ret = -EALREADY;
goto fail;