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From: Shakeel Butt To: "Vlastimil Babka (SUSE)" Cc: Sebastian Andrzej Siewior , Andrew Morton , Johannes Weiner , Michal Hocko , Roman Gushchin , Muchun Song , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Thomas Gleixner Subject: Re: [PATCH v2] memcg: simple cleanup of stats update functions Message-ID: References: <20240420232505.2768428-1-shakeel.butt@linux.dev> <20240527152200.P1rU7FaG@linutronix.de> <86006806-4ffc-4330-ab4b-29215ab2c98c@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <86006806-4ffc-4330-ab4b-29215ab2c98c@kernel.org> X-Migadu-Flow: FLOW_OUT X-Rspam-User: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: A57D840016 X-Stat-Signature: inh6penhoo839rnjhjkj8xjk17gj6ujr X-HE-Tag: 1716873408-57480 X-HE-Meta: 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 FNuhQscB SEMbzJOGKSvwR4oYv4qYQbFNwIHJfzHPsvZobxmADrWrgDnr9oIP9A2fxY74Gfy0HSRwYPP+Vlwh1yv3Z/MqxlyKlpvkFSlE4NgJOq+zLM1bSq48tMM6BLC6grQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, 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, May 27, 2024 at 06:34:24PM GMT, Vlastimil Babka (SUSE) wrote: > On 5/27/24 5:22 PM, Sebastian Andrzej Siewior wrote: > > On 2024-04-20 16:25:05 [-0700], Shakeel Butt wrote: > >> mod_memcg_lruvec_state() is never called from outside of memcontrol.c > >> and with always irq disabled. So, replace it with the irq disabled > >> version and add an assert that irq is disabled in the caller. > > > > unless PREEMPT_RT is enabled. In that case IRQs are not disabled as part > > of local_lock_irqsave(&memcg_stock.stock_lock, …) leading to: Sorry about that and thanks for the report. > > But then the "interrupts are handled by a kernel thread that can sleep" part > of RT also means it's ok to just have the stock_lock taken with no > interrupts disabled as no actual raw interrupt handler will interrupt the > holder and deadlock, right? > Thanks Vlastimil for jolting my memory on RT reasoning. > > | ------------[ cut here ]------------ > > | WARNING: CPU: 0 PID: 1 at mm/memcontrol.c:3150 __mod_objcg_mlstate+0xc2/0x110 > > | CPU: 0 PID: 1 Comm: systemd Not tainted 6.10.0-rc1-rt0+ #17 > > | Call Trace: > > | > > | mod_objcg_state+0x2b3/0x320 > > | __memcg_slab_post_alloc_hook+0x13c/0x340 > > | kmem_cache_alloc_lru_noprof+0x2bd/0x2e0 > > | alloc_inode+0x59/0xc0 > > | iget_locked+0xf0/0x290 > > > > suggestions? > > So in that case the appropriate thing would be to replace the assert with > lockdep_assert_held(&memcg_stock.stock_lock); > ? > > It seems all the code paths leading here have that one. > Yeah this seems right and reasonable. Should I send a fix or you want to send it?