linux-kernel - [PATCH] mm, oom: document oom

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Message-Id: <20180711120121.25635-1-mhocko@kernel.org>
Date:   Wed, 11 Jul 2018 14:01:21 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     David Rientjes <rientjes@...gle.com>,
        Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
        <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>,
        Michal Hocko <mhocko@...e.com>
Subject: [PATCH] mm, oom: document oom_lock

From: Michal Hocko <mhocko@...e.com>

Add a short documentation about what is the oom_lock scope.

Requested-by: David Rientjes <rientjes@...gle.com>
Signed-off-by: Michal Hocko <mhocko@...e.com>
---
 mm/oom_kill.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index ed9d473c571e..32e6f7becb40 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -53,6 +53,14 @@ int sysctl_panic_on_oom;
 int sysctl_oom_kill_allocating_task;
 int sysctl_oom_dump_tasks = 1;
 
+/*
+ * Serializes oom killer invocations (out_of_memory()) from all contexts to
+ * prevent from over eager oom killing (e.g. when the oom killer is invoked
+ * from different domains).
+ *
+ * oom_killer_disable() relies on this lock to stabilize oom_killer_disabled
+ * and mark_oom_victim
+ */
 DEFINE_MUTEX(oom_lock);
 
 #ifdef CONFIG_NUMA
-- 
2.18.0