1 files changed, 13 insertions, 11 deletions

diff --git a/mm/vmscan.c b/mm/vmscan.c
index bd9a72bc4a1b..ab2505c3ef54 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -2921,18 +2921,20 @@ static bool prepare_kswapd_sleep(pg_data_t *pgdat, int order, long remaining,
                 return false;
 
         /*
-         * There is a potential race between when kswapd checks its watermarks
-         * and a process gets throttled. There is also a potential race if
-         * processes get throttled, kswapd wakes, a large process exits therby
-         * balancing the zones that causes kswapd to miss a wakeup. If kswapd
-         * is going to sleep, no process should be sleeping on pfmemalloc_wait
-         * so wake them now if necessary. If necessary, processes will wake
-         * kswapd and get throttled again
+         * The throttled processes are normally woken up in balance_pgdat() as
+         * soon as pfmemalloc_watermark_ok() is true. But there is a potential
+         * race between when kswapd checks the watermarks and a process gets
+         * throttled. There is also a potential race if processes get
+         * throttled, kswapd wakes, a large process exits thereby balancing the
+         * zones, which causes kswapd to exit balance_pgdat() before reaching
+         * the wake up checks. If kswapd is going to sleep, no process should
+         * be sleeping on pfmemalloc_wait, so wake them now if necessary. If
+         * the wake up is premature, processes will wake kswapd and get
+         * throttled again. The difference from wake ups in balance_pgdat() is
+         * that here we are under prepare_to_wait().
          */
-        if (waitqueue_active(&pgdat->pfmemalloc_wait)) {
-                wake_up(&pgdat->pfmemalloc_wait);
-                return false;
-        }
+        if (waitqueue_active(&pgdat->pfmemalloc_wait))
+                wake_up_all(&pgdat->pfmemalloc_wait);
 
         return pgdat_balanced(pgdat, order, classzone_idx);
 }