diff options
| author | Sebastian Andrzej Siewior <bigeasy@linutronix.de> | 2022-03-22 14:40:50 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2022-03-22 15:57:03 -0700 |
| commit | 0790ed623847bbdd440ae29cc01da81c99834ea5 (patch) | |
| tree | d120e342d4ac8622de7f98c6b945a8b8c923c0a0 /mm/memcontrol.c | |
| parent | 5675114623872300aa9fcd72aef2b8b7f421fe12 (diff) | |
mm/memcg: disable migration instead of preemption in drain_all_stock().
Before the for-each-CPU loop, preemption is disabled so that so that
drain_local_stock() can be invoked directly instead of scheduling a
worker. Ensuring that drain_local_stock() completed on the local CPU is
not correctness problem. It _could_ be that the charging path will be
forced to reclaim memory because cached charges are still waiting for
their draining.
Disabling preemption before invoking drain_local_stock() is problematic
on PREEMPT_RT due to the sleeping locks involved. To ensure that no CPU
migrations happens across for_each_online_cpu() it is enouhg to use
migrate_disable() which disables migration and keeps context preemptible
to a sleeping lock can be acquired. A race with CPU hotplug is not a
problem because pcp data is not going away. In the worst case we just
schedule draining of an empty stock.
Use migrate_disable() instead of get_cpu() around the
for_each_online_cpu() loop.
Link: https://lkml.kernel.org/r/20220226204144.1008339-7-bigeasy@linutronix.de
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: kernel test robot <oliver.sang@intel.com>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Michal Koutný <mkoutny@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Roman Gushchin <roman.gushchin@linux.dev>
Cc: Shakeel Butt <shakeelb@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vladimir Davydov <vdavydov.dev@gmail.com>
Cc: Waiman Long <longman@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/memcontrol.c')
| -rw-r--r-- | mm/memcontrol.c | 5 |
1 files changed, 3 insertions, 2 deletions
diff --git a/mm/memcontrol.c b/mm/memcontrol.c index fa381d892422..85a259515e91 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -2300,7 +2300,8 @@ static void drain_all_stock(struct mem_cgroup *root_memcg) * as well as workers from this path always operate on the local * per-cpu data. CPU up doesn't touch memcg_stock at all. */ - curcpu = get_cpu(); + migrate_disable(); + curcpu = smp_processor_id(); for_each_online_cpu(cpu) { struct memcg_stock_pcp *stock = &per_cpu(memcg_stock, cpu); struct mem_cgroup *memcg; @@ -2323,7 +2324,7 @@ static void drain_all_stock(struct mem_cgroup *root_memcg) schedule_work_on(cpu, &stock->work); } } - put_cpu(); + migrate_enable(); mutex_unlock(&percpu_charge_mutex); } |