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From: Shakeel Butt To: Sebastian Andrzej Siewior Cc: "Vlastimil Babka (SUSE)" , 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: Remove the lockdep assert from __mod_objcg_mlstate(). Message-ID: References: <20240528121928.i-Gu7Jvg@linutronix.de> <09e085bb-f09e-4901-a2dd-a0b789bb8a4d@kernel.org> <20240528134027.OxDASsS3@linutronix.de> <20240528141341.rz_rytN_@linutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240528141341.rz_rytN_@linutronix.de> X-Migadu-Flow: FLOW_OUT X-Rspamd-Queue-Id: 0FEB8140006 X-Stat-Signature: u4k9yte36wguuh6knfg6utifht58ibp5 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1716913325-983960 X-HE-Meta: U2FsdGVkX19tbj6+POqXmY1nXZzIHgV9J+qjXoE4+WLHWbiMeupr/H+7//2Ulr5kY6NmA3XBBV/KW1jB735jTNoWw189+/K4/6HVWC+13pZlSvxlLbxOcJdHoLm2w+C8VBKGQoapnUcCwPFfNXi2RuMlWYQNA/P+uAYCKWdC3nbH98UgUCx/rtmFC2jZfp5ot11Jw0VsQyR/T5SLsrng1InaC1D/EkDGXz9LmtpdJK0woj9gZPWxGVDXsCSbOVMwVUA7TmBUMw17FVUbLg5JPfvkz7+6UCqBHp0ca9ifde1b1yKsRKACsNZmSYco45u25NR7hUf87EUmx1mbXOB91S3PSuVeJ9T+M44BQEgUx0qbR8yL73ecKtnbe6leyxr1KXbDeeCZI0RB3MnzWCrFJPrLAVcd8YSDwKAjOMIaJRSNR0AvbctH0B7ct4rDpzXfsrvt82sAHFH/KgteI1rOMeo4tWau6g3R9s8pNpe7usgitz/wlJCq4WwoV5xSBPW/M5gW+7sjIY85Kx71xXDHxdHEyv55a4gEsjhqTrXzn+OAaykHQm4mjT7rkwXgo/FNU5NhI373aXJhYjJBjhgF/l8W6+Gjb4e5zkBLrEKYnnS7zwe05OL+kV76aQoos+X2TO2EStSeo7r4qTcEy0DAx9zU/HkOdJLgEj0RQw2WJFMt/Dw4VibniGhl0+dJRbnFRPWufoDISDM1cHCAhdHVN9pk0r4MdB7AEmgbepk7dzkMGWwiwAx4lU4vBhcFFSrRMGWyiS8Sv/CBt9LXi2WDf0gjGdaRmq1NuLXxiK1PSGttUqgyBVSgEc9t+GVRzTMLfvhn0+XofzNU7XhcHdFbt38xdZDGjC+q3EFg/pUmwmjsOZ9GQJVAnGtL2Wu1Vk9XYi3lHSZEDKt0UioF9Orghr8pzp75xz8URDPZFih9zmNXCUSkqwZan9HBrBL0k6L7eAhAXI4deWuWcVOMg3I A6kGxLQM kHBW7y1/eI32p0pVBmgFckw8mndAxOZxLOu07V5F9lNUQfQjXp/zvBr6RNe+xt0OA75hfnvYq03Lyy0JvBA/6wAJDTSdQLhgKh9tY6GHAv0RXemF+Dg294slp969Wn5kYZZwW/B/UtSLKEsS4XEktqwtBNCr3qlCnvnaDG/uCNJbpDU5l77VLz6fwBGzcAdDSHQfa 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 Tue, May 28, 2024 at 04:13:41PM GMT, Sebastian Andrzej Siewior wrote: > The assert was introduced in the commit cited below as an insurance that > the semantic is the same after the local_irq_save() has been removed and > the function has been made static. > > The original requirement to disable interrupt was due the modification > of per-CPU counters which require interrupts to be disabled because the > counter update operation is not atomic and some of the counters are > updated from interrupt context. > > All callers of __mod_objcg_mlstate() acquire a lock > (memcg_stock.stock_lock) which disables interrupts on !PREEMPT_RT and > the lockdep assert is satisfied. On PREEMPT_RT the interrupts are not > disabled and the assert triggers. > > The safety of the counter update is already ensured by > VM_WARN_ON_IRQS_ENABLED() which is part of __mod_memcg_lruvec_state() and > does not require yet another check. > > Remove the lockdep assert from __mod_objcg_mlstate(). > > Fixes: 91882c1617c15 ("memcg: simple cleanup of stats update functions") > Link: https://lore.kernel.org/r/20240528121928.i-Gu7Jvg@linutronix.de > Signed-off-by: Sebastian Andrzej Siewior Acked-by: Shakeel Butt