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dmarc=none (p=none dis=none) header.from=arm.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:Message-ID:Date: In-reply-to:Subject:To:From:References:Reply-To:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Owner; bh=0MObsaG10ImEih6yv5CRH+Lrg62Kg30DNuze1qzPzwA=; b=X303VG/zxpY2TmGCH9pVAObfc2 KU4taMW/GrK+q7eOjQEW6/I/TyPstByYg9Vl28dP1DIA54JMSsyxgU+DCXvK42Fpkpawnz2AnvVC/ gyvzh+iG0DRwV0wXKYdZCl3p7dDv0YaHCFl+2XmyRP9tjBgJrN3/DjwAI7LvYp/fMsm8h1NVo8EIF D+XKfzxQmGVS42zud8Yl5cp5SwzCiNZeQBNtp//klX02LTMWK59mwW1HkE8fgSZj1a/4fTxwLeqlS 2wIWbqRNAaF/L2j4emw5njOy6gP8/B13Dl2AYv3+9D7naC3Wct1UxcueGQUanh5LwOiUSSIo/CtbG oWNxmAEQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jMUU0-0007Sa-33; Thu, 09 Apr 2020 10:32:28 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1jMUTw-0007RL-Sq for linux-arm-kernel@lists.infradead.org; Thu, 09 Apr 2020 10:32:26 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 312DF31B; Thu, 9 Apr 2020 03:32:22 -0700 (PDT) Received: from e113632-lin (e113632-lin.cambridge.arm.com [10.1.194.46]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id DE0FD3F73D; Thu, 9 Apr 2020 03:32:18 -0700 (PDT) References: <855831b59e1b3774b11c3e33050eac4cc4639f06.1583332765.git.vpillai@digitalocean.com> <20200401114215.36640-1-cj.chengjian@huawei.com> <20200409095941.GA25948@bogus> User-agent: mu4e 0.9.17; emacs 26.3 From: Valentin Schneider To: Sudeep Holla Subject: Re: [PATCH] sched/arm64: store cpu topology before notify_cpu_starting In-reply-to: <20200409095941.GA25948@bogus> Date: Thu, 09 Apr 2020 11:32:12 +0100 Message-ID: MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200409_033224_974381_F3D281F0 X-CRM114-Status: GOOD ( 17.21 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: joelaf@google.com, Cheng Jian , peterz@infradead.org, fweisbec@gmail.com, huawei.libin@huawei.com, joel@joelfernandes.org, mingo@kernel.org, aubrey.li@linux.intel.com, naravamudan@digitalocean.com, aaron.lwe@gmail.com, torvalds@linux-foundation.org, jdesfossez@digitalocean.com, w.f@huawei.com, pawan.kumar.gupta@linux.intel.com, pjt@google.com, kerrnel@google.com, keescook@chromium.org, xiexiuqi@huawei.com, vpillai@digitalocean.com, tglx@linutronix.de, linux-arm-kernel@lists.infradead.org, pauld@redhat.com, mgorman@techsingularity.net, linux-kernel@vger.kernel.org, aubrey.intel@gmail.com, pbonzini@redhat.com, tim.c.chen@linux.intel.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 09/04/20 10:59, Sudeep Holla wrote: > On Wed, Apr 01, 2020 at 02:23:33PM +0100, Valentin Schneider wrote: >> >> (+LAKML, +Sudeep) >> > > Thanks Valentin. > >> On Wed, Apr 01 2020, Cheng Jian wrote: >> > when SCHED_CORE enabled, sched_cpu_starting() uses thread_sibling as >> > SMT_MASK to initialize rq->core, but only after store_cpu_topology(), >> > the thread_sibling is ready for use. >> > >> > notify_cpu_starting() >> > -> sched_cpu_starting() # use thread_sibling >> > >> > store_cpu_topology(cpu) >> > -> update_siblings_masks # set thread_sibling >> > >> > Fix this by doing notify_cpu_starting later, just like x86 do. >> > >> >> I haven't been following the sched core stuff closely; can't this >> rq->core assignment be done in sched_cpu_activate() instead? We already >> look at the cpu_smt_mask() in there, and it is valid (we go through the >> entirety of secondary_start_kernel() before getting anywhere near >> CPUHP_AP_ACTIVE). >> > > I too came to same conclusion. Did you see any issues ? Or is it > just code inspection in parity with x86 ? > With mainline this isn't a problem; with the core scheduling stuff there is an expectation that we can use the SMT masks in sched_cpu_starting(). >> I don't think this breaks anything, but without this dependency in >> sched_cpu_starting() then there isn't really a reason for this move. >> > > Based on the commit message, had a quick look at x86 code and I agree > this shouldn't break anything. However the commit message does make > complete sense to me, especially reference to sched_cpu_starting > while smt_masks are accessed in sched_cpu_activate. Or am I missing > to understand something here ? As stated above, it's not a problem for mainline, and AIUI we can change the core scheduling bits to only use the SMT mask in sched_cpu_activate() instead, therefore not requiring any change in the arch code. I'm not aware of any written rule that the topology masks should be usable from a given hotplug state upwards, only that right now we need them in sched_cpu_(de)activate() for SMT scheduling - and that is already working fine. So really this should be considering as a simple neutral cleanup; I don't really have any opinion on picking it up or not. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel