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Received: from [2601:18c:8100:a0e0:5a47:caff:fe78:8708] by shelob.surriel.com with esmtpsa (TLS1.3) tls TLS_AES_256_GCM_SHA384 (Exim 4.99.5) (envelope-from ) id 1wzy0A-000000090vY-2pUQ; Fri, 28 Aug 2026 14:56:18 +0000 Message-ID: <34c252862494db8432c702efec4543daa11ff392.camel@surriel.com> Subject: Re: [PATCH] mm/memcontrol: avoid stuck FLUSHING_CACHED_CHARGE bit on isolated cpus From: Rik van Riel To: Michal Hocko Cc: linux-kernel@vger.kernel.org, Johannes Weiner , Roman Gushchin , Shakeel Butt , Muchun Song , Andrew Morton , cgroups@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com, stable@vger.kernel.org Date: Fri, 28 Aug 2026 10:56:17 -0400 In-Reply-To: References: Autocrypt: addr=riel@surriel.com; prefer-encrypt=mutual; keydata=mQENBFIt3aUBCADCK0LicyCYyMa0E1lodCDUBf6G+6C5UXKG1jEYwQu49cc/gUBTTk33A eo2hjn4JinVaPF3zfZprnKMEGGv4dHvEOCPWiNhlz5RtqH3SKJllq2dpeMS9RqbMvDA36rlJIIo47 Z/nl6IA8MDhSqyqdnTY8z7LnQHqq16jAqwo7Ll9qALXz4yG1ZdSCmo80VPetBZZPw7WMjo+1hByv/ lvdFnLfiQ52tayuuC1r9x2qZ/SYWd2M4p/f5CLmvG9UcnkbYFsKWz8bwOBWKg1PQcaYHLx06sHGdY dIDaeVvkIfMFwAprSo5EFU+aes2VB2ZjugOTbkkW2aPSWTRsBhPHhV6dABEBAAG0HlJpayB2YW4gU mllbCA8cmllbEByZWRoYXQuY29tPokBHwQwAQIACQUCW5LcVgIdIAAKCRDOed6ShMTeg05SB/986o gEgdq4byrtaBQKFg5LWfd8e+h+QzLOg/T8mSS3dJzFXe5JBOfvYg7Bj47xXi9I5sM+I9Lu9+1XVb/ r2rGJrU1DwA09TnmyFtK76bgMF0sBEh1ECILYNQTEIemzNFwOWLZZlEhZFRJsZyX+mtEp/WQIygHV WjwuP69VJw+fPQvLOGn4j8W9QXuvhha7u1QJ7mYx4dLGHrZlHdwDsqpvWsW+3rsIqs1BBe5/Itz9o 6y9gLNtQzwmSDioV8KhF85VmYInslhv5tUtMEppfdTLyX4SUKh8ftNIVmH9mXyRCZclSoa6IMd635 Jq1Pj2/Lp64tOzSvN5Y9zaiCc5FucXtB9SaWsgdmFuIFJpZWwgPHJpZWxAc3VycmllbC5jb20+iQE +BBMBAgAoBQJSLd2lAhsjBQkSzAMABgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAAKCRDOed6ShMTe g4PpB/0ZivKYFt0LaB22ssWUrBoeNWCP1NY/lkq2QbPhR3agLB7ZXI97PF2z/5QD9Fuy/FD/jddPx KRTvFCtHcEzTOcFjBmf52uqgt3U40H9GM++0IM0yHusd9EzlaWsbp09vsAV2DwdqS69x9RPbvE/Ne fO5subhocH76okcF/aQiQ+oj2j6LJZGBJBVigOHg+4zyzdDgKM+jp0bvDI51KQ4XfxV593OhvkS3z 3FPx0CE7l62WhWrieHyBblqvkTYgJ6dq4bsYpqxxGJOkQ47WpEUx6onH+rImWmPJbSYGhwBzTo0Mm G1Nb1qGPG+mTrSmJjDRxrwf1zjmYqQreWVSFEt26tBpSaWsgdmFuIFJpZWwgPHJpZWxAZmIuY29tP okBPgQTAQIAKAUCW5LbiAIbIwUJEswDAAYLCQgHAwIGFQgCCQoLBBYCAwECHgECF4AACgkQznneko TE3oOUEQgAsrGxjTC1bGtZyuvyQPcXclap11Ogib6rQywGYu6/Mnkbd6hbyY3wpdyQii/cas2S44N cQj8HkGv91JLVE24/Wt0gITPCH3rLVJJDGQxprHTVDs1t1RAbsbp0XTksZPCNWDGYIBo2aHDwErhI omYQ0Xluo1WBtH/UmHgirHvclsou1Ks9jyTxiPyUKRfae7GNOFiX99+ZlB27P3t8CjtSO831Ij0Ip QrfooZ21YVlUKw0Wy6Ll8EyefyrEYSh8KTm8dQj4O7xxvdg865TLeLpho5PwDRF+/mR3qi8CdGbkE c4pYZQO8UDXUN4S+pe0aTeTqlYw8rRHWF9TnvtpcNzZw== Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.60.2 (3.60.2-1.fc44) MIME-Version: 1.0 X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 9B997100004 X-Stat-Signature: t3y558bzrbzhjd1n6pdwb9fsoter667r X-HE-Tag: 1787928989-268690 X-HE-Meta: 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 VoIrBl0G A6jPF4p9F1sUAG5JSrsr7h8n/NWij1SIn+p4ZkFJc1pGj5kB8pAd/geS/D0rP93z8zT+OgQ5VEDKoqaN5PirMKn/iL+UO3RNpXNAt6jgHcu4hLaezIQnArhviFSljEUO634mqJ7wCXxE3BLtiJiew1svLSK6j0d9pn+fw8PLeCVVRd2AuYVEdSOOAeqVOwUHIvtQyV8AnfYdgE0scwYMhq2FGN2HBPKga4PlFNZwmYeALccBvu9ulNF423hbKI/c10NwXmHCQHKe8ln+HVTNiPs/K4E3q86xv5ow3ZtDcFBzCfvgq7i/HeEc777pYlI5spSyXJIlOy2QAXq9zUaveBWDM7rKZ5Z8OW55q Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 2026-08-28 at 16:25 +0200, Michal Hocko wrote: > On Fri 28-08-26 09:46:21, Rik van Riel wrote: > > drain_all_stock() can leave FLUSHING_CACHED_CHARGE set after the > > work is dropped.=C2=A0 It sets the bit before checking isolation and > > schedule_drain_work() checks isolation and queues in a separate RCU > > critical section, so housekeeping_update()'s synchronize_rcu() can > > race the second check. > >=20 > > drain_local_stock() only clears the bit for work that ran, so the > > bit > > remains set and the stock is never drained again. > >=20 > > Reorganize the drain_all_stock() loop, reducing nesting, splitting > > out local vs remote cpu handling, and skipping everything on > > isolated > > cpus, which solves the stuck FLUSHING_CACHED_CHARGE flag. >=20 > Is there any reason why we cannot simply clear the flag if the work > is > not scheduled? >=20 That should work, too. I'm fine with whatever variant people prefer. --=20 All Rights Reversed.