From mboxrd@z Thu Jan 1 00:00:00 1970 From: Daniel Wagner Subject: [PATCH RT 6/7] Revert "memcontrol: Prevent scheduling while atomic in cgroup code" Date: Wed, 4 Apr 2018 09:16:51 +0200 Message-ID: <20180404071652.24196-7-wagi@monom.org> References: <20180404071652.24196-1-wagi@monom.org> Cc: linux-rt-users , Steven Rostedt , Thomas Gleixner , Carsten Emde , John Kacur , Paul Gortmaker , Julia Cartwright , Daniel Wagner , tom.zanussi@linux.intel.com, stable@vger.kernel.org, Sebastian Andrzej Siewior To: linux-kernel@vger.kernel.org Return-path: In-Reply-To: <20180404071652.24196-1-wagi@monom.org> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-rt-users.vger.kernel.org From: "Steven Rostedt (VMware)" 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: Reported-by: Haiyang HY1 Tan Signed-off-by: Steven Rostedt (VMware) [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 --- 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