memcg: memcg_rstat_updated re-entrant safe against irqs

Patch series "memcg: make memcg stats irq safe", v2.

This series converts memcg stats to be irq safe i.e.  memcg stats can be
updated in any context (task, softirq or hardirq) without disabling the
irqs.  This is still not nmi-safe on all architectures but after this
series converting memcg charging and stats nmi-safe will be easier.


This patch (of 7):

memcg_rstat_updated() is used to track the memcg stats updates for
optimizing the flushes.  At the moment, it is not re-entrant safe and the
callers disabled irqs before calling.  However to achieve the goal of
updating memcg stats without irqs, memcg_rstat_updated() needs to be
re-entrant safe against irqs.

This patch makes memcg_rstat_updated() re-entrant safe using this_cpu_*
ops.  On archs with CONFIG_ARCH_HAS_NMI_SAFE_THIS_CPU_OPS, this patch is
also making memcg_rstat_updated() nmi safe.

[[email protected]: fix build]
  Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Shakeel Butt <[email protected]>
Signed-off-by: Lorenzo Stoakes <[email protected]>
Reviewed-by: Vlastimil Babka <[email protected]>
Tested-by: Alexei Starovoitov <[email protected]>
Cc: Johannes Weiner <[email protected]>
Cc: Michal Hocko <[email protected]>
Cc: Muchun Song <[email protected]>
Cc: Roman Gushchin <[email protected]>
Cc: Sebastian Andrzej Siewior <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

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