ipc, shm: make shmem attach/detach wait for mmap_sem killable

shmat and shmdt rely on 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. Signed-off-by: Michal Hocko <[email protected]> Acked-by: Davidlohr Bueso <[email protected]> Acked-by: Vlastimil Babka <[email protected]> Cc: Hugh Dickins <[email protected]> Signed-off-by: Andrew Morton <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
chewitt · May 24, 2016 · 91f4f94 · 91f4f94
1 parent 7c05126
commit 91f4f94
Showing 1 changed file with 7 additions and 2 deletions.
diff --git a/ipc/shm.c b/ipc/shm.c
@@ -1200,7 +1200,11 @@ long do_shmat(int shmid, char __user *shmaddr, int shmflg, ulong *raddr,
 	if (err)
 		goto out_fput;
 
-	down_write(&current->mm->mmap_sem);
+	if (down_write_killable(&current->mm->mmap_sem)) {
+		err = -EINTR;
+		goto out_fput;
+	}
+
 	if (addr && !(shmflg & SHM_REMAP)) {
 		err = -EINVAL;
 		if (addr + size < addr)
@@ -1271,7 +1275,8 @@ SYSCALL_DEFINE1(shmdt, char __user *, shmaddr)
 	if (addr & ~PAGE_MASK)
 		return retval;
 
-	down_write(&mm->mmap_sem);
+	if (down_write_killable(&mm->mmap_sem))
+		return -EINTR;
 
 	/*
 	 * This function tries to be smart and unmap shm segments that