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Tue, 11 Mar 2025 08:30:33 -0700 (PDT) Date: Tue, 11 Mar 2025 11:30:32 -0400 From: Johannes Weiner To: Shakeel Butt Cc: Andrew Morton , Michal Hocko , Roman Gushchin , Muchun Song , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Meta kernel team , stable@vger.kernel.org Subject: Re: [PATCH] memcg: drain obj stock on cpu hotplug teardown Message-ID: <20250311153032.GB1211411@cmpxchg.org> References: <20250310230934.2913113-1-shakeel.butt@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250310230934.2913113-1-shakeel.butt@linux.dev> X-Rspam-User: X-Rspamd-Queue-Id: BAC2C1C0035 X-Rspamd-Server: rspam03 X-Stat-Signature: bzfjk5qpupfhjrmzjeb1dmxo3uu4jiwf X-HE-Tag: 1741707035-572428 X-HE-Meta: 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 i+OzwvFJ ehZEoUvQrqtbfrRFyo6cfKcLf4T/zkAP1bjpZKOlX+TxpNj+1AytaDKzXWWsiw/EQhO2k9r9c3dMPsDsP/xK2KmkOj3nDttr6dRtVDFKjLenExNEzk/fWN98p4+PgAoELQ0lBLryAjNkU9vwzavqNt8GEdpC/RJOc2rLnmaFt1dRAjHWivo2YeXVmuDVz6R2lSZDnk8lGc7d3XGseyPheakHGZFY3MpkVCuLNxRzR4x2IEQNB2l+yInsWXm7jgKftn9cuf4UUjz4f+von3yQd97FaS80sngIG3OSY19E5LH8qDAdIGQTeohrDz9PBp/6d1Zk71+oGgy5bWg6AWyHPGoHaAKgpunkxTeBvB7Bqsh2DNJiYqJhw/6ZF6cVMC0f7IAz4IHhd4vS4psUYhpEjqmmbExFvjrP6iFic0WPEUJy0CnWpgGboBxTNN92Aftvy0+1hWsM8ECWIQw39lMwsAqNLdgLXWNW4NAy0F89fbzxC3S8= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000008, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Mar 10, 2025 at 04:09:34PM -0700, Shakeel Butt wrote: > Currently on cpu hotplug teardown, only memcg stock is drained but we > need to drain the obj stock as well otherwise we will miss the stats > accumulated on the target cpu as well as the nr_bytes cached. The stats > include MEMCG_KMEM, NR_SLAB_RECLAIMABLE_B & NR_SLAB_UNRECLAIMABLE_B. In > addition we are leaking reference to struct obj_cgroup object. > > Fixes: bf4f059954dc ("mm: memcg/slab: obj_cgroup API") > Signed-off-by: Shakeel Butt > Cc: Wow, that's old. Good catch. > --- > mm/memcontrol.c | 9 +++++++++ > 1 file changed, 9 insertions(+) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 4de6acb9b8ec..59dcaf6a3519 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -1921,9 +1921,18 @@ void drain_all_stock(struct mem_cgroup *root_memcg) > static int memcg_hotplug_cpu_dead(unsigned int cpu) > { > struct memcg_stock_pcp *stock; > + struct obj_cgroup *old; > + unsigned long flags; > > stock = &per_cpu(memcg_stock, cpu); > + > + /* drain_obj_stock requires stock_lock */ > + local_lock_irqsave(&memcg_stock.stock_lock, flags); > + old = drain_obj_stock(stock); > + local_unlock_irqrestore(&memcg_stock.stock_lock, flags); > + > drain_stock(stock); > + obj_cgroup_put(old); It might be better to call drain_local_stock() directly instead. That would prevent a bug of this type to reoccur in the future.