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authorMichal Hocko <mhocko@suse.cz>2013-07-31 20:53:51 (GMT)
committerChanho Park <chanho61.park@samsung.com>2014-11-18 02:47:22 (GMT)
commit12e330b1b532171cd7805df385b3773ddbf6a8e3 (patch)
treeaf538b4f703cf47a03b173b39cb1b78d43df747f /mm
parentadc01eaeab3f25c9ada5930a3168dc90c362dfe5 (diff)
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vmpressure: make sure there are no events queued after memcg is offlined
vmpressure is called synchronously from reclaim where the target_memcg is guaranteed to be alive but the eventfd is signaled from the work queue context. This means that memcg (along with vmpressure structure which is embedded into it) might go away while the work item is pending which would result in use-after-release bug. We have two possible ways how to fix this. Either vmpressure pins memcg before it schedules vmpr->work and unpin it in vmpressure_work_fn or explicitely flush the work item from the css_offline context (as suggested by Tejun). This patch implements the later one and it introduces vmpressure_cleanup which flushes the vmpressure work queue item item. It hooks into mem_cgroup_css_offline after the memcg itself is cleaned up. [akpm@linux-foundation.org: coding-style fixes] Signed-off-by: Michal Hocko <mhocko@suse.cz> Reported-by: Tejun Heo <tj@kernel.org> Cc: Anton Vorontsov <anton.vorontsov@linaro.org> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com> Cc: Li Zefan <lizefan@huawei.com> Acked-by: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Change-Id: I1deefca16b6e243f86bd78b84c561db02e7a20e8
Diffstat (limited to 'mm')
-rw-r--r--mm/memcontrol.c1
-rw-r--r--mm/vmpressure.c16
2 files changed, 17 insertions, 0 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index f45e21a..c0b33c2 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -6344,6 +6344,7 @@ static void mem_cgroup_css_offline(struct cgroup *cont)
mem_cgroup_reparent_charges(memcg);
mem_cgroup_destroy_all_caches(memcg);
+ vmpressure_cleanup(&memcg->vmpressure);
}
static void mem_cgroup_css_free(struct cgroup *cont)
diff --git a/mm/vmpressure.c b/mm/vmpressure.c
index 192f973..0c1e37d 100644
--- a/mm/vmpressure.c
+++ b/mm/vmpressure.c
@@ -372,3 +372,19 @@ void vmpressure_init(struct vmpressure *vmpr)
INIT_LIST_HEAD(&vmpr->events);
INIT_WORK(&vmpr->work, vmpressure_work_fn);
}
+
+/**
+ * vmpressure_cleanup() - shuts down vmpressure control structure
+ * @vmpr: Structure to be cleaned up
+ *
+ * This function should be called before the structure in which it is
+ * embedded is cleaned up.
+ */
+void vmpressure_cleanup(struct vmpressure *vmpr)
+{
+ /*
+ * Make sure there is no pending work before eventfd infrastructure
+ * goes away.
+ */
+ flush_work(&vmpr->work);
+}