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Fri, 13 Dec 2024 14:02:07 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id 66GzAl8+XGeEFQAAD6G6ig (envelope-from ); Fri, 13 Dec 2024 14:02:07 +0000 Message-ID: Date: Fri, 13 Dec 2024 15:02:06 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next v2 3/6] locking/local_lock: Introduce local_trylock_irqsave() Content-Language: en-US From: Vlastimil Babka To: Alexei Starovoitov Cc: bpf , Andrii Nakryiko , Kumar Kartikeya Dwivedi , Andrew Morton , Peter Zijlstra , Sebastian Sewior , Steven Rostedt , Hou Tao , Johannes Weiner , shakeel.butt@linux.dev, Michal Hocko , Matthew Wilcox , Thomas Gleixner , Tejun Heo , linux-mm , Kernel Team , Jann Horn References: <20241210023936.46871-1-alexei.starovoitov@gmail.com> <20241210023936.46871-4-alexei.starovoitov@gmail.com> <1c760bf1-14a4-42e4-a55b-438a29987aef@suse.cz> <9e5bdef1-a692-47d5-82b9-96a4f2c68463@suse.cz> <60fadf5a-4c96-43b3-8cc2-baf71eb93e3f@suse.cz> Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 09D954001C X-Stat-Signature: i7sbox7c89asgyi5h3zrwifemcnqkymk X-HE-Tag: 1734098499-863196 X-HE-Meta: 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 QkfC7d/f pt3gRKGo1CCNQUUKI27VSVM3CGzgQ24zN28t/XxbOXA4EyS5ZRNE7OeaBkiACQTZSPBxiiMeO6p5AvbaPGBx0ftGYak0eWl9o+mTiUX8gr0LWusDEyO/Zaim3Typ+ku8T1hfaQPYodCkwe1zxQaaiZdHQQUcA8Hzbrb87NZ/DOs5FcqA/rXP9N42Y98OKRFYHwIU2Amn4xf4u7psnuZPw4SXJkvl1Xp1rrohDgvX7LspYDQz6UKx+JEVIkS9LAwCSS0gjgw/b0Tmdmt3QV0t2JrfFF7qKv3GWoit3FRxs+o8k1qmYCAEYGET3rqNkf5hQVDtsQlYVXs9wVZDm5D0hBzvi4gB0JMtj172OAuk5zNaaPMy3sC1bnZkNHzBJbejlrVws5n2pkb6JWpc3KBhc4dBNTxB/CbhLxCndqO5lfz/agjg= 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 12/12/24 10:15, Vlastimil Babka wrote: > On 12/12/24 03:49, Alexei Starovoitov wrote: >> I like your >> +struct local_tryirq_lock >> approach, but let's put it in local_lock.h ? > > Sure, that was a proof of concept so kept it local. > >> and it probably needs local_inc_return() instead of READ/WRITE_ONCE. >> With irq and nmis it's racy. > > Hm guess you are right, thanks! > Ah I remember now, the idea was that if an irq or nmi interrupts someone else between checking that active is 0 and setting it to 1, it will finish the critical section and unlock before the interrupted context can continue, so the race is harmless.