lkml.org 
[lkml]   [2018]   [Apr]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH RT 6/7] Revert "memcontrol: Prevent scheduling while atomic in cgroup code"
Date
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@CNMAILEX04.lenovo.com
]
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);
}

/*
--
2.14.3
\
 
 \ /
  Last update: 2018-04-04 09:17    [W:0.060 / U:12.416 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site