From: "Steven Rostedt (VMware)" <rostedt@xxxxxxxxxxx>
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@xxxxxxxxxxxxxxx>
Reported-by: Haiyang HY1 Tan <tanhy1@xxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
[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@xxxxxxxxxxxxxxxxxxxxx
]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
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);
}
/*
--
2.14.3