4.9.65-rt57-rc1 stable review patch. If anyone has any objections, please let me know.

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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 | 13 ++++++------- 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 12b94909ba7b..c04403033aec 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -1698,7 +1698,6 @@ struct memcg_stock_pcp { #define FLUSHING_CACHED_CHARGE 0 }; static DEFINE_PER_CPU(struct memcg_stock_pcp, memcg_stock); -static DEFINE_LOCAL_IRQ_LOCK(memcg_stock_ll); static DEFINE_MUTEX(percpu_charge_mutex);

/** @@ -1721,7 +1720,7 @@ static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages) if (nr_pages > CHARGE_BATCH) return ret;

- local_lock_irqsave(memcg_stock_ll, flags); + local_irq_save(flags);

stock = this_cpu_ptr(&memcg_stock); if (memcg == stock->cached && stock->nr_pages >= nr_pages) { @@ -1729,7 +1728,7 @@ static bool consume_stock(struct mem_cgroup *memcg, unsigned int nr_pages) ret = true; }

- local_unlock_irqrestore(memcg_stock_ll, flags); + local_irq_restore(flags);

return ret; } @@ -1756,13 +1755,13 @@ static void drain_local_stock(struct work_struct *dummy) struct memcg_stock_pcp *stock; unsigned long flags;

- local_lock_irqsave(memcg_stock_ll, flags); + local_irq_save(flags);

stock = this_cpu_ptr(&memcg_stock); drain_stock(stock); clear_bit(FLUSHING_CACHED_CHARGE, &stock->flags);

- local_unlock_irqrestore(memcg_stock_ll, flags); + local_irq_restore(flags); }

/* @@ -1774,7 +1773,7 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) struct memcg_stock_pcp *stock; unsigned long flags;

- local_lock_irqsave(memcg_stock_ll, flags); + local_irq_save(flags);

stock = this_cpu_ptr(&memcg_stock); if (stock->cached != memcg) { /* reset if necessary */ @@ -1783,7 +1782,7 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) } stock->nr_pages += nr_pages;

- local_unlock_irqrestore(memcg_stock_ll, flags); + local_irq_restore(flags); }

/*