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Fri, 28 Aug 2026 19:26:20 +0000 X-Mizu-Trace-ID: d6f9c93dfcbab706 X-Migadu-Flow: FLOW_OUT Date: Fri, 28 Aug 2026 12:26:15 -0700 From: Shakeel Butt To: Andrew Morton Cc: Rik van Riel , linux-kernel@vger.kernel.org, Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , cgroups@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com Subject: Re: [PATCH v2] mm/memcontrol: fix stuck FLUSHING_CACHED_CHARGE bit on isolated cpus Message-ID: References: <20260828135036.7d44361f@fangorn> <20260828122018.1a3b3be204212837fcda8e50@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260828122018.1a3b3be204212837fcda8e50@linux-foundation.org> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 0F86DA0007 X-Stat-Signature: h8xddxtcid55qnjt5y5crxtkrq15c4ur X-Rspam-User: X-HE-Tag: 1787945181-937105 X-HE-Meta: U2FsdGVkX18VGUGiWJZmbRiYYhL0/9srPtNcgBFaJF3iWoD6uPKe4Xa6hpf79xT+W3UPJll+SuKNh+bugWDLNrheD5Xqojge++YdAjQ/2R2ur5pNj2UV01adWZwOa4DUEqBdaDXPhZt5ws3teQvECoIdeNZEjS4dMVMHVZEDon9oprbg6wpeBe0eP/fo2EL879QwRFqKK+i8kGecVZLi2cQ0ajW0u8aL5upWC9Oz8DbwMHDeYOR34YvVeOJeV+eiuhsiXZmENqwfTr75ggPNidIGWfoKzXJNeL5FvYODQtg06ZHCq9Eo7uK4xwjQYN9WRX+LCiMAxOctbyczjT/+Ww6La0DM6eiAx5U3y+SHeIs4Fx5N4IS81JNTxEDLn9CJclw4skgW9mchFuWfJQmPZU4bua3UZNRo8zlXy5geZ2OmUS5MEgGwDxuxRs+KKnDgkrSmaEhNtTBikURoT1Shd9TPfcKw42yS86OBQ/E5hbkKP5PqUFPJ41Z1bTrvmkzr33ucDM0nwps7GtY91WhZbnQdtD+KJ4MHMr9IS16+D+ERiVja40etz9bXtAvQd6NWpG4Axonhopzwlz/HCC9uZvaIn7gF2I1QkaJ9Q20MgMFpx68lhc5sEb1r99JwTZ5AUFsLxn5uzgOiPjE91E44UZWMonNf+JprUkg7KD4Nx3elrQKrtrD6Rt/KyysbhCaiSAugwS96zb43jylgi0/lJV5gbjGQrzpO7DYwGs0sfBOGxDXSdx3CWan2V+nzN1SQaLswBiuhPeWlR5nrTGE5/fTTaTYiBjHp6CgpkOXy3Zx24u9xsXYDju3b3W+MK4iy4NSnML/H70VBE26G0USo813OFcGsljgs4yPbrG0lfZ7dm2MQV4TaODuzNzzbGvAy/AMYpN9pfYHyRZ9bsdtBaJaTqpVvuZtBw99gcSnxrcymkYo+bSzrZ7POnTy8ZspuShtgLm8IbK2Ca/BsO/L xatFzJRF 3XwCwvKVKtKqpHRKu1cL7n/T81eS3YG9OIcanSKQu+kZmW2u0A1kIvSi5wMy1ys6h71DH/5RHz0HIvTnWjrMnC1rQ2EhqA3/wAjA3GJ5S/zeYAmRynCsp58QIcIZHylnwNxapaf44ReJhWpQxdROMegaik4hSn+zqN+35+fhCQwvooMC0HGtJZm+w7fH8oSEM3sjWP4O/kKcot6ukRs7MujX/LfMz9Ln5EPh1dJvXc9qbwFX7rZKT/ogXIpz3X90sz2WwIV4aa32AQqWzzrV1O+6qO7o8Oim+gZD1kxWeUWrIGaxsSdhZhMUTVPj/Vlg31vSfsBXosjSIbog67x+uwO3A9eqLCd2g5yHO9IyZj5+CBXqWMFKSSC0vd7v3SfkxkNu5aNhhu2dnNVOwywANtEa2LLhDEZQeB7101jFZx3PKQo0LJhilyYU8eLGHCEX5fT4mF8kBrv2vR3rMzaY/MvZ2+w== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Aug 28, 2026 at 12:20:18PM -0700, Andrew Morton wrote: > On Fri, 28 Aug 2026 13:50:36 -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. > > 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@vger.kernel.org > > 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 Haha we are never done. Just sent the fix for this new report: http://lore.kernel.org/20260828192419.3057939-1-shakeel.butt@linux.dev