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Fri, 14 Feb 2025 12:15:53 +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 ZRZdKPkzr2dzcgAAD6G6ig (envelope-from ); Fri, 14 Feb 2025 12:15:53 +0000 Message-ID: Date: Fri, 14 Feb 2025 13:15:53 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH bpf-next v8 3/6] locking/local_lock: Introduce localtry_lock_t To: Alexei Starovoitov Cc: bpf , Andrii Nakryiko , Kumar Kartikeya Dwivedi , Andrew Morton , Peter Zijlstra , Sebastian Sewior , Steven Rostedt , Hou Tao , Johannes Weiner , Shakeel Butt , Michal Hocko , Matthew Wilcox , Thomas Gleixner , Jann Horn , Tejun Heo , linux-mm , Kernel Team References: <20250213033556.9534-1-alexei.starovoitov@gmail.com> <20250213033556.9534-4-alexei.starovoitov@gmail.com> <1fda7391-228d-4e10-8449-189be36eb27c@suse.cz> Content-Language: en-US From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Action: no action X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 7A246100010 X-Stat-Signature: kao84xo3jtry5dgmgy9dzs1oe1dhedqf X-Rspam-User: X-HE-Tag: 1739535365-823872 X-HE-Meta: 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 zz1zIWuY SEqrPDMrVEw6dxRsglQch82TDENCEsDMNkX8QN2UbWZ/QAk3P3Geuak2VL7MVOjH9VRIjR7V3fmB/juVjBkhOOM4hZylTnc7ovt11Ry4RzDGVr+dbT0+++8YeVS5esg04ftlpDyyknAk5eOQYoXh9YR9uyfqD9Ji3MhvYB/Sno9l+o70HlQfq5vFkqS0grCmtaSND3T19BeecHk/9EwhlL3JN7p2UjAaZ/oomJxN2NxAntMCmBZXr4RZyDO7SS24xn7S3FxjEqYFk/74jU++yTSfUX3Hlmvm2GeqfnCUHkKLdvgp4Y9JLnmn0J20QNhL9rONCN7SXxErJz20YCGJTeLvrxvRIs+TGN7TIqNSbYaVGHq7evNRy4o/f92knA1NdKSZDDt+8rR6QdFQ= 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 2/13/25 16:23, Alexei Starovoitov wrote: > On Thu, Feb 13, 2025 at 7:04 AM Vlastimil Babka wrote: >> >> >> > + >> > +#define __localtry_trylock_irqsave(lock, flags) \ >> > + ({ \ >> > + int __locked; \ >> > + \ >> > + typecheck(unsigned long, flags); \ >> > + flags = 0; \ >> > + if (in_nmi() | in_hardirq()) { \ >> > + __locked = 0; \ >> >> Because of this, IIUC? > > Right. > It's part of commit log: > + 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. > > Steven explained it in detail in some earlier thread. > > realtime is hard. bpf and realtime together are even harder. > Things got much better over the years, but plenty of work ahead. > I can go in detail, but offtopic for this thread. Thanks, it's fine. Just that the comment of the function could be more clear then, so people don't have to check implementation/commit log/lore discussions :)