[PATCH 14/18] prctl: make PR_SET_THP_DISABLE wait for mmap_sem killable

[Michal Hocko]

From: Michal Hocko <mhocko@xxxxxxxx>

PR_SET_THP_DISABLE requires 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: Alex Thorlton <athorlton@xxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Michal Hocko <mhocko@xxxxxxxx>
---
 kernel/sys.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/sys.c b/kernel/sys.c
index cf8ba545c7d3..89d5be418157 100644
--- a/kernel/sys.c
+++ b/kernel/sys.c
@@ -2246,7 +2246,8 @@ SYSCALL_DEFINE5(prctl, int, option, unsigned long, arg2, unsigned long, arg3,
 	case PR_SET_THP_DISABLE:
 		if (arg3 || arg4 || arg5)
 			return -EINVAL;
-		down_write(&me->mm->mmap_sem);
+		if (down_write_killable(&me->mm->mmap_sem))
+			return -EINTR;
 		if (arg2)
 			me->mm->def_flags |= VM_NOHUGEPAGE;
 		else
-- 
2.8.0.rc3