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

[Andrew Morton]

On Fri, 28 Aug 2026 13:50:36 -0400 Rik van Riel <riel@xxxxxxxxxxx> 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.

Is there some Reported-by: or reproducer for this?

Given the complexity of the reproducers which Gemini developed for me, I'm
suspecting "nope".

> Fixes: 6a792697a53a ("memcg: do not drain charge pcp caches on remote isolated cpus")
> Cc: stable@xxxxxxxxxxxxxxx

Why is a backport being proposed?  How does that benefit those we
serve?

Sashiko suggests that we ain't done yet:
	https://sashiko.dev/#/patchset/20260828135036.7d44361f@fangorn