Merge tag 'v4.9.56' into linux-linaro-lsk-v4.9

 This is the 4.9.56 stable release

1 files changed, 16 insertions, 0 deletions

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index ec9f11d4f094..d631d251c150 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -37,6 +37,7 @@
 #include <linux/ratelimit.h>
 #include <linux/kthread.h>
 #include <linux/init.h>
+#include <linux/mmu_notifier.h>
 
 #include <asm/tlb.h>
 #include "internal.h"
@@ -491,6 +492,21 @@ static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
 	}
 
 	/*
+	 * If the mm has notifiers then we would need to invalidate them around
+	 * unmap_page_range and that is risky because notifiers can sleep and
+	 * what they do is basically undeterministic.  So let's have a short
+	 * sleep to give the oom victim some more time.
+	 * TODO: we really want to get rid of this ugly hack and make sure that
+	 * notifiers cannot block for unbounded amount of time and add
+	 * mmu_notifier_invalidate_range_{start,end} around unmap_page_range
+	 */
+	if (mm_has_notifiers(mm)) {
+		up_read(&mm->mmap_sem);
+		schedule_timeout_idle(HZ);
+		goto unlock_oom;
+	}
+
+	/*
 	 * increase mm_users only after we know we will reap something so
 	 * that the mmput_async is called only when we have reaped something
 	 * and delayed __mmput doesn't matter that much