linux-kernel - [PATCH v2] mm: terminate shrink_slab loop if signal is pending

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Date:   Thu,  7 Dec 2017 17:23:05 -0800
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     akpm@...ux-foundation.org, mhocko@...e.com, hannes@...xchg.org,
        hillf.zj@...baba-inc.com, minchan@...nel.org,
        mgorman@...hsingularity.net, ying.huang@...el.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Cc:     timmurray@...gle.com, tkjos@...gle.com,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: [PATCH v2] mm: terminate shrink_slab loop if signal is pending

Slab shrinkers can be quite time consuming and when signal
is pending they can delay handling of the signal. If fatal
signal is pending there is no point in shrinking that process
since it will be killed anyway. This change checks for pending
fatal signals inside shrink_slab loop and if one is detected
terminates this loop early.

Signed-off-by: Suren Baghdasaryan <surenb@...gle.com>

---
V2:
Sergey Senozhatsky:
  - Fix missing parentheses
---
 mm/vmscan.c | 7 +++++++
 1 file changed, 7 insertions(+)

diff --git a/mm/vmscan.c b/mm/vmscan.c
index c02c850ea349..28e4bdc72c16 100644
--- a/mm/vmscan.c
+++ b/mm/vmscan.c
@@ -486,6 +486,13 @@ static unsigned long shrink_slab(gfp_t gfp_mask, int nid,
 			.memcg = memcg,
 		};
 
+		/*
+		 * We are about to die and free our memory.
+		 * Stop shrinking which might delay signal handling.
+		 */
+		if (unlikely(fatal_signal_pending(current)))
+			break;
+
 		/*
 		 * If kernel memory accounting is disabled, we ignore
 		 * SHRINKER_MEMCG_AWARE flag and call all shrinkers
-- 
2.15.1.424.g9478a66081-goog