From: "Steven Rostedt (VMware)" rostedt@goodmis.org

The commit "memcontrol: Prevent scheduling while atomic in cgroup code" fixed this issue:

refill_stock() get_cpu_var() drain_stock() res_counter_uncharge() res_counter_uncharge_until() spin_lock() <== boom

But commit 3e32cb2e0a12b ("mm: memcontrol: lockless page counters") replaced the calls to res_counter_uncharge() in drain_stock() to the lockless function page_counter_uncharge(). There is no more spin lock there and no more reason to have that local lock.

Cc: stable@vger.kernel.org Reported-by: Haiyang HY1 Tan tanhy1@lenovo.com Signed-off-by: Steven Rostedt (VMware) rostedt@goodmis.org [bigeasy: That upstream commit appeared in v3.19 and the patch in question in v3.18.7-rt2 and v3.18 seems still to be maintained. So I guess that v3.18 would need the locallocks that we are about to remove here. I am not sure if any earlier versions have the patch backported. The stable tag here is because Haiyang reported (and debugged) a crash in 4.4-RT with this patch applied (which has get_cpu_light() instead the locallocks it gained in v4.9-RT). https://lkml.kernel.org/r/05AA4EC5C6EC1D48BE2CDCFF3AE0B8A637F78A15@CNMAILEX0... ] Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de --- mm/memcontrol.c | 7 ++----- 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 493b4986d5dc..56f67a15937b 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1925,17 +1925,14 @@ static void drain_local_stock(struct work_struct *dummy) */ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) { - struct memcg_stock_pcp *stock; - int cpu = get_cpu_light(); - - stock = &per_cpu(memcg_stock, cpu); + struct memcg_stock_pcp *stock = &get_cpu_var(memcg_stock);

if (stock->cached != memcg) { /* reset if necessary */ drain_stock(stock); stock->cached = memcg; } stock->nr_pages += nr_pages; - put_cpu_light(); + put_cpu_var(memcg_stock); }

/*