[Devel] [PATCH rh7 2/5] mm: memcontrol: check more carefully if current is oom killed

[Vladimir Davydov]

Currently, we abort memcg reclaim only if fatal_signal_pending returns
true on current. That's not enough, because a process can be killed
after it entered do_exit, in which case signal_pending may not be set
and therefore an OOM killed process may be looping in mem_cgroup_reclaim
for quite some time (the latter retries reclaim 100 times!), resulting
in OOM timeout at best or soft lockup panic at worst.

Let's elaborate the abort condition by adding TIF_MEMDIE check.

Signed-off-by: Vladimir Davydov <vdavydov at virtuozzo.com>
---
 mm/memcontrol.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index 9ccc8080c2e0..b2543e69ccf7 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c
@@ -2088,7 +2088,8 @@ static unsigned long mem_cgroup_reclaim(struct mem_cgroup *memcg,
 			drain_all_stock_async(memcg);
 		total += try_to_free_mem_cgroup_pages(memcg, SWAP_CLUSTER_MAX,
 						      gfp_mask, noswap);
-		if (fatal_signal_pending(current))
+		if (test_thread_flag(TIF_MEMDIE) ||
+		    fatal_signal_pending(current))
 			return 1;
 		/*
 		 * Allow limit shrinkers, which are triggered directly
@@ -2939,7 +2940,8 @@ again:
 		bool invoke_oom = oom && !nr_oom_retries;
 
 		/* If killed, bypass charge */
-		if (fatal_signal_pending(current)) {
+		if (test_thread_flag(TIF_MEMDIE) ||
+		    fatal_signal_pending(current)) {
 			css_put(&memcg->css);
 			goto bypass;
 		}
-- 
2.1.4