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Goncalves" , Andrew Morton , Boqun Feng , Ingo Molnar , John Ogness , Mel Gorman , Peter Zijlstra , Thomas Gleixner , Waiman Long , Will Deacon Subject: Re: [PATCH v2 1/2] seqlock: Do the lockdep annotation before locking in do_write_seqcount_begin_nested() Message-ID: References: <20230623171232.892937-2-bigeasy@linutronix.de> <20230626081254.XmorFrhs@linutronix.de> <20230727151029.e_M9bi8N@linutronix.de> <649fa1a7-4efd-8cc7-92c7-ac7944adc283@I-love.SAKURA.ne.jp> <60d4dc52-9281-9266-4294-b514bd09e6e8@I-love.SAKURA.ne.jp> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <60d4dc52-9281-9266-4294-b514bd09e6e8@I-love.SAKURA.ne.jp> X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: CE7531C0013 X-Stat-Signature: ej4x6ayhz8wga1cckqw3sfokoerg4d8s X-Rspam-User: X-HE-Tag: 1691074196-978666 X-HE-Meta: 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 9U85pKDa GiMa/O6jjEJyshO3mnMJ9uGBNaOZNlelbD/UAvHUUokiwE7TT+1kM/WfcivmIflXWfoPLK2Ts0yzCLHehXD2otPxuQ1+96pq11OMojD9MxkPLvFv3r/ecofJBuo9ypfkf0od/tFVftBrxC4rir7mgMKsyLTWkzBexSyPezNFzs+oW/7v9XDmw18K9umaAYShpKsOGMByd3w6ovqSBBSPqyEE6rIC4EHl4IB0V2goAqHauZ1xq9faSIJw+G0Qr8Teh1ECRV/gjVrbAgLEeklfCw1HDjT1+YcbQg8MpCc31hDVtPicR0inuPjJOP5yqK4TjLxqF44UZqaog7u4= 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: On Thu 03-08-23 22:18:10, Tetsuo Handa wrote: > On 2023/07/31 23:25, Michal Hocko wrote: > > On Sat 29-07-23 20:05:43, Tetsuo Handa wrote: > >> On 2023/07/29 14:31, Tetsuo Handa wrote: > >>> On 2023/07/28 0:10, Sebastian Andrzej Siewior wrote: > >>>> On 2023-06-28 21:14:16 [+0900], Tetsuo Handa wrote: > >>>>>> Anyway, please do not do this change only because of printk(). > >>>>>> IMHO, the current ordering is more logical and the printk() problem > >>>>>> should be solved another way. > >>>>> > >>>>> Then, since [PATCH 1/2] cannot be applied, [PATCH 2/2] is automatically > >>>>> rejected. > >>>> > >>>> My understanding is that this patch gets applied and your objection will > >>>> be noted. > >>> > >>> My preference is that zonelist_update_seq is not checked by !__GFP_DIRECT_RECLAIM > >>> allocations, which is a low-hanging fruit towards GFP_LOCKLESS mentioned at > >>> https://lkml.kernel.org/r/ZG3+l4qcCWTPtSMD@dhcp22.suse.cz and > >>> https://lkml.kernel.org/r/ZJWWpGZMJIADQvRS@dhcp22.suse.cz . > >>> > >>> Maybe we can defer checking zonelist_update_seq till retry check like below, > >>> for this is really an infrequent event. > >>> > >> > >> An updated version with comments added. > > > > Seriously, don't you see how hairy all this is? And for what? Nitpicking > > something that doesn't seem to be a real problem in the first place? > > Seriously, can't you find "zonelist_update_seq is not checked by !__GFP_DIRECT_RECLAIM > allocations, which is a low-hanging fruit towards GFP_LOCKLESS" !? I do not think we have concluded that we want to support GFP_LOCKLESS. This might be trivial straightforward now but it imposes some constrains for future maintainability. So far we haven't heard about many usecases where this would be needed and a single one is not sufficient IMHO. -- Michal Hocko SUSE Labs