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b=VrbhhsTdLKdbOwEKULirDK4Nw7Gzj6RISy0LqKnBxKaSjYkZigZs6+UrOwzV5Z/cC FmNTF7biBmZDCliUf9HuuCWn2sgT7hLuO9L1/t0pPMmP7/458parRN0QUAoeawflCM uCQGhIe/ZPJYDOI9gqcdsUyih6ijuDvLyFnY3Qdocl3g71HCQNOddccnr0Q64SEM7F aKyItkPy2gy7TjXp0YU99f80Ureu79e+nucezFSjH6vlWZA/TvZRgP4ZYezHIKUL2m VX+d/qMDZnZEBKsmQ5mzwxrFHC8gC3GRhMFPKA/GwYnVik27VdTgaeM/sXyya2t7UM Rup5ZNdNiiv9A== Date: Sat, 12 Apr 2025 00:00:03 +0200 From: Frederic Weisbecker To: Oleg Nesterov Cc: LKML , Andrew Morton , Ingo Molnar , Marcelo Tosatti , Michal Hocko , Peter Zijlstra , Thomas Gleixner , Valentin Schneider , Vlastimil Babka , linux-mm@kvack.org Subject: Re: [PATCH 5/6] sched/isolation: Introduce isolated task work Message-ID: References: <20250410152327.24504-1-frederic@kernel.org> <20250410152327.24504-6-frederic@kernel.org> <20250411102555.GA5322@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20250411102555.GA5322@redhat.com> X-Stat-Signature: 9cixb5sexdcajgtnae3amhz431scbnzx X-Rspam-User: X-Rspamd-Queue-Id: D7BCB1A0011 X-Rspamd-Server: rspam08 X-HE-Tag: 1744408807-94114 X-HE-Meta: U2FsdGVkX19IEqVdHUNhl2M7FVtMIQy8lYVzxKpIn+7AIdARfPR2a063twZpSiAvgOscHQy1cCEqwicuC0Xlt0ZlkDsfLUeK05JjiOr6IBmstw6CbfjRmUFeJ+emHJLTguDkr6mt/sbuKe3QuGCRo6Y/wriTe60V2LY0Y+H3uuskRSSrnVni4KebW7SUVG0EA0DnFny9S4MxjyvajYNHu5yuvsm7HklUHTqoTaseYs8s5K72LmdwnW8XBH/bbVfmXoNkNvjNV+Mcyxoeh9ChItQsx8/Rn6ylwAh/NFtlfvzHAImbcTX6WItrNDpFVoxZr2N6iYfjGV0ly898cHVv2di4dx39in4h5U8w6Woyy+MNdNr5pHzos4fjsaCrfO6icguHR5IJtNwMFWTZ5cK/auHKNPuMoMzVfe0ZYyCnX21O8pWY2eM3GEko4zP5CEA8pOsM5stJFMwwOoW+x9fPVRzQ5RIdbfh6w5sO/FP8cIc27v1pTD7KCrtldBKSI6UappwlHUtOisoVFlI4jhJizdE/VRyu8HtUzxrozatpRVBHGeqcziYvIN8ZZlCnnfaTM93BvJnUNh7QnD87N9OghlodK+OoGeQMNhnyL2TecfWu49JlENI9fHSd/kWJLJ/i3ErFXAyTCjpP3/cMAQanqKsf7EFDo3mWXxcRb0Ekrp94BrQ/ZIGh0rulAQhn204AzkxzdutxAk13r8y0DrlwnGnIUyQNKLUja1yNpIaQ0q9gRobmIpACMcy47Nud5QYGV/p0Fu1JykF/Mx7GYYYrzw/+nvWcGESkf2MN9n/FumpococBg7Na7f1OTApFjQqYl9GxkSdJL2UtpTCCHO66xijmdjrair+tn8FFnjqz+JY0rI0DV6zIrrStr9wwPGgehr6OIF8jIDgKlVkhJ1ft1RSlKrVdHJNhvM5mK9jFQuGtLRwiI0auiRZq41iyDDGt98i7r+RUe5rW88QnwEL voWxf9DD tEZlueq+bf0sHT36ZlGoSWMfa5ZkjKBI+mxV9pe1Coci/DS64oDTkRyYVnXoQdC/Dt/DGS+/jOGrfBl5cxOBSOFsKehF8rEs2clnYwDkiGYemtv2w/1wlqnKmPobJ8IQUaek2Ou2YhjD8D9xjrpvArtZpqcRPcFEqPCIaJC0XD4ElNs5XYeCzK77MGiigOtO1Q2qjtH4t34nxohBqt6Loxm2PDXaO/k0U6RGR99ujlkWMf50= 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: Le Fri, Apr 11, 2025 at 12:25:56PM +0200, Oleg Nesterov a écrit : > I know nothing about this code so I can't review, but let me > ask anyway... > > On 04/10, Frederic Weisbecker wrote: > > > > +int __isolated_task_work_queue(void) > > +{ > > + unsigned long flags; > > + int ret; > > + > > + if (current->flags & PF_KTHREAD) > > + return -EINVAL; > > What about PF_USER_WORKER's ? IIUC, these (in fact kernel) threads > never return to userspace and never call task_work_run(). Ah good catch! (though I'm having a hard time finding out what this is about)... > > Or PF_IO_WORKER's, they too run only in kernel mode... But iirc they > do call task_work_run(). At least I see a lot of task_work usage in io_uring, and there are some explicit calls to task_work_run() there... > > > + local_irq_save(flags); > > + if (task_work_queued(¤t->nohz_full_work)) { > > + ret = 0; > > + goto out; > > + } > > + > > + ret = task_work_add(current, ¤t->nohz_full_work, TWA_RESUME); > > +out: > > + local_irq_restore(flags); > > + return ret; > > Hmm, why not > > local_irq_save(flags); > if (task_work_queued(...)) > ret = 0; > else > ret = task_work_add(...); Hehe, yes indeed! Thanks! -- Frederic Weisbecker SUSE Labs