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mm, oom: document oom_lock

Message ID 20180711120121.25635-1-mhocko@kernel.org (mailing list archive)
State New, archived
Headers show

Commit Message

Michal Hocko July 11, 2018, 12:01 p.m. UTC 
From: Michal Hocko <mhocko@suse.com>

Add a short documentation about what is the oom_lock scope.

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

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