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Re: [PATCH 1/3] mm: memcontrol: make per-cpu charge cache IRQ-safe for socket accounting

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On Wed, Sep 14, 2016 at 03:48:44PM -0400, Johannes Weiner wrote:
> From: Johannes Weiner <jweiner@fb.com>
> 
> During cgroup2 rollout into production, we started encountering css
> refcount underflows and css access crashes in the memory controller.
> Splitting the heavily shared css reference counter into logical users
> narrowed the imbalance down to the cgroup2 socket memory accounting.
> 
> The problem turns out to be the per-cpu charge cache. Cgroup1 had a
> separate socket counter, but the new cgroup2 socket accounting goes
> through the common charge path that uses a shared per-cpu cache for
> all memory that is being tracked. Those caches are safe against
> scheduling preemption, but not against interrupts - such as the newly
> added packet receive path. When cache draining is interrupted by
> network RX taking pages out of the cache, the resuming drain operation
> will put references of in-use pages, thus causing the imbalance.
> 
> Disable IRQs during all per-cpu charge cache operations.
> 
> Fixes: f7e1cb6ec51b ("mm: memcontrol: account socket memory in unified hierarchy memory controller")
> Cc: <stable@vger.kernel.org> # 4.5+
> Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>

Acked-by: Vladimir Davydov <vdavydov.dev@gmail.com>

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[PATCH 1/3] mm: memcontrol: make per-cpu charge cache IRQ-safe for socket accounting Johannes Weiner <hannes@cmpxchg.org> - 2016-09-14 22:00 +0200
  Re: [PATCH 1/3] mm: memcontrol: make per-cpu charge cache IRQ-safe  for socket accounting Michal Hocko <mhocko@kernel.org> - 2016-09-19 14:10 +0200
  Re: [PATCH 1/3] mm: memcontrol: make per-cpu charge cache IRQ-safe  for socket accounting Vladimir Davydov <vdavydov.dev@gmail.com> - 2016-09-19 17:40 +0200

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