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Wysocki" , kernel-team@android.com References: <20210518105951.GC7770@willie-the-truck> <20210520101640.GA10065@willie-the-truck> <0dbdfe1e-dede-d33d-ca89-768a1fa3c907@arm.com> <8bc24850-3a14-5dd2-fbc2-bf745616949f@arm.com> <20210520180318.GB10523@willie-the-truck> From: Dietmar Eggemann Message-ID: <2055b1d4-ef42-0f49-6a0c-40c8415ef945@arm.com> Date: Fri, 21 May 2021 13:26:10 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: <20210520180318.GB10523@willie-the-truck> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210521_042629_413381_CE521725 X-CRM114-Status: GOOD ( 17.53 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 20/05/2021 20:03, Will Deacon wrote: > Hi Dietmar, > > On Thu, May 20, 2021 at 07:55:27PM +0200, Dietmar Eggemann wrote: >> On 20/05/2021 18:00, Daniel Bristot de Oliveira wrote: >>> On 5/20/21 5:06 PM, Dietmar Eggemann wrote: >>>> (1) # chrt -d -T 5000000 -P 16666666 0 ./32bit_app >>>> >>>> (2) # ./32bit_app & >>>> >>>> # chrt -d -T 5000000 -P 16666666 -p 0 pid_of(32bit_app) >>>> >>>> >>>> Wouldn't the behaviour of (1) and (2) be different w/o this patch? >>>> >>>> In (1) __sched_setscheduler() happens before execve so it operates on >>>> p->cpus_ptr equal span. >>>> >>>> In (2) span != p->cpus_ptr so DL AC will fail. >>>> >>> >>> As far as I got, the case (1) would be spitted in two steps: >>> >>> - __sched_setscheduler() will work, then >>> - execv() would fail because (span != p->cpus_ptr) >>> >>> So... at the end, both (1) and (2) would result in a failure... >>> >>> am I missing something? >> >> Not sure. Reading this thread I was under the assumption that the only >> change would be the drop of this patch. But I assume there is also this >> 'if DL AC is on then let sched_setattr() fail for this 32bit task'. >> >> IMHO, the current patch-stack w/o this patch should let (1) succeed with >> DL AC. > > That's what I'm proposing, yes, but others (including Daniel) prefer to > fail the execve(). See my other reply just now for a summary [1]. [...] Thanks, Will ... Now I understand. Or at least I think I do ;-) > [1] https://lore.kernel.org/lkml/20210520180138.GA10523@willie-the-truck/T/#u _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel