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a=rsa-sha256; c=relaxed/relaxed; d=stgolabs.net; s=dreamhost; t=1740589258; bh=rrBHkoNYX1SE8vJwLOW7Vd34VXpCljs+VmhE2AbWq7Q=; h=Date:From:To:Cc:Subject:Content-Type; b=H9Z+9Vz+cD+MI0Pi9BowQUIIe0YJ/pcjIXzsZElUUQwt48i4fukX0C1XtiYX/8E9n KFsRP216yCoNSmcAQx6aaq+nt5L9b7zk/zvov0kzU1ucYiXYYcIr17geZqofGYPB9E 7CZ6MlfAUTsHjq7k1VWNhPteHHQsPSwQ1fvaMlp/vTN0lVA7Ir+rTPGoiAMOgAaJv6 BS1q8azoySijrHL1iqMv4TaGT6tKcGyR4DA12BUMjt4LN28ET5/AIIGRmgNvMnvpqg P+hr59fJZmlvO3tSIPeCDEY6mvOF4vK2x00fe+spu29gFFjyKvOsdx2IxAWaObUw+D qIPWGENLtOC0g== Date: Wed, 26 Feb 2025 09:00:53 -0800 From: Davidlohr Bueso To: Vlastimil Babka Cc: Suren Baghdasaryan , "Liam R. Howlett" , Christoph Lameter , David Rientjes , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Uladzislau Rezki , linux-mm@kvack.org, linux-kernel@vger.kernel.org, rcu@vger.kernel.org, maple-tree@lists.infradead.org, Sebastian Andrzej Siewior , Alexei Starovoitov Subject: Re: [PATCH RFC v2 03/10] locking/local_lock: Introduce localtry_lock_t Message-ID: <20250226170053.lxpreaegz5tysef7@offworld> Mail-Followup-To: Vlastimil Babka , Suren Baghdasaryan , "Liam R. Howlett" , Christoph Lameter , David Rientjes , Roman Gushchin , Hyeonggon Yoo <42.hyeyoo@gmail.com>, Uladzislau Rezki , linux-mm@kvack.org, linux-kernel@vger.kernel.org, rcu@vger.kernel.org, maple-tree@lists.infradead.org, Sebastian Andrzej Siewior , Alexei Starovoitov References: <20250214-slub-percpu-caches-v2-0-88592ee0966a@suse.cz> <20250214-slub-percpu-caches-v2-3-88592ee0966a@suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20250214-slub-percpu-caches-v2-3-88592ee0966a@suse.cz> User-Agent: NeoMutt/20220429 X-Stat-Signature: 531oxsufyxhjrfbwix34kp8basqfaqeq X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 61C8F120038 X-Rspam-User: X-HE-Tag: 1740589261-263772 X-HE-Meta: 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 JxjgK5jG 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000327, 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 Fri, 14 Feb 2025, Vlastimil Babka wrote: >From: Sebastian Andrzej Siewior > >In !PREEMPT_RT local_lock_irqsave() disables interrupts to protect >critical section, but it doesn't prevent NMI, so the fully reentrant >code cannot use local_lock_irqsave() for exclusive access. > >Introduce localtry_lock_t and localtry_lock_irqsave() that >disables interrupts and sets acquired=1, so localtry_lock_irqsave() >from NMI attempting to acquire the same lock will return false. > >In PREEMPT_RT local_lock_irqsave() maps to preemptible spin_lock(). >Map localtry_lock_irqsave() to preemptible spin_trylock(). >When in hard IRQ or NMI return false right away, since >spin_trylock() is not safe due to PI issues. > >Note there is no need to use local_inc for acquired variable, >since it's a percpu variable with strict nesting scopes. > LGTM. Acked-by: Davidlohr Bueso