|author||Michal Hocko <email@example.com>||2014-10-20 18:12:32 +0200|
|committer||Greg Kroah-Hartman <firstname.lastname@example.org>||2014-11-14 08:47:58 -0800|
OOM, PM: OOM killed task shouldn't escape PM suspend
commit 5695be142e203167e3cb515ef86a88424f3524eb upstream. PM freezer relies on having all tasks frozen by the time devices are getting frozen so that no task will touch them while they are getting frozen. But OOM killer is allowed to kill an already frozen task in order to handle OOM situtation. In order to protect from late wake ups OOM killer is disabled after all tasks are frozen. This, however, still keeps a window open when a killed task didn't manage to die by the time freeze_processes finishes. Reduce the race window by checking all tasks after OOM killer has been disabled. This is still not race free completely unfortunately because oom_killer_disable cannot stop an already ongoing OOM killer so a task might still wake up from the fridge and get killed without freeze_processes noticing. Full synchronization of OOM and freezer is, however, too heavy weight for this highly unlikely case. Introduce and check oom_kills counter which gets incremented early when the allocator enters __alloc_pages_may_oom path and only check all the tasks if the counter changes during the freezing attempt. The counter is updated so early to reduce the race window since allocator checked oom_killer_disabled which is set by PM-freezing code. A false positive will push the PM-freezer into a slow path but that is not a big deal. Changes since v1 - push the re-check loop out of freeze_processes into check_frozen_processes and invert the condition to make the code more readable as per Rafael Fixes: f660daac474c6f (oom: thaw threads if oom killed thread is frozen before deferring) Signed-off-by: Michal Hocko <email@example.com> Signed-off-by: Rafael J. Wysocki <firstname.lastname@example.org> Signed-off-by: Greg Kroah-Hartman <email@example.com>
Diffstat (limited to 'mm')
2 files changed, 25 insertions, 0 deletions
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 8e40908e724a..f104c7e9f61e 100644
@@ -402,6 +402,23 @@ static void dump_header(struct task_struct *p, gfp_t gfp_mask, int order,
+ * Number of OOM killer invocations (including memcg OOM killer).
+ * Primarily used by PM freezer to check for potential races with
+ * OOM killed frozen task.
+static atomic_t oom_kills = ATOMIC_INIT(0);
+ return atomic_read(&oom_kills);
#define K(x) ((x) << (PAGE_SHIFT-10))
* Must be called while holding a reference to p, which will be released upon
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 71305c6aba5b..494a081ec5e4 100644
@@ -2120,6 +2120,14 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
+ * PM-freezer should be notified that there might be an OOM killer on
+ * its way to kill and wake somebody up. This is too early and we might
+ * end up not killing anything but false positives are acceptable.
+ * See freeze_processes.
* Go through the zonelist yet one more time, keep very high watermark
* here, this is only to catch a parallel oom killing, we must fail if
* we're still under heavy pressure.