Re: [PATCH v2] mm/memcontrol: fix stuck FLUSHING_CACHED_CHARGE bit on isolated cpus

[Shakeel Butt]

On Fri, Aug 28, 2026 at 01:50:36PM -0400, Rik van Riel wrote:
> When drain_all_stock() sets FLUSHING_CACHED_CHARGE before checking
> isolation, schedule_drain_work() can drop the work in a separate RCU
> critical section, and housekeeping_update()'s synchronize_rcu() can race
> that second check, leaving the flag set.
> 
> drain_local_stock() only clears the bit for work that ran, so the flag
> remains set and the stock is never drained again.
> 
> Have schedule_drain_work() return whether the work was queued, and clear
> FLUSHING_CACHED_CHARGE in drain_all_stock() when the remote CPU is
> isolated, so future drains can retry.
> 
> Fixes: 6a792697a53a ("memcg: do not drain charge pcp caches on remote isolated cpus")
> Cc: stable@xxxxxxxxxxxxxxx
> Suggested-by: Michal Hocko <mhocko@xxxxxxxx>
> Suggested-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>
> Signed-off-by: Rik van Riel <riel@xxxxxxxxxxx>

Acked-by: Shakeel Butt <shakeel.butt@xxxxxxxxx>