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[209.85.220.65]) by mx.google.com with SMTPS id 93sor82115566wrb.13.2019.01.29.10.31.51 for (Google Transport Security); Tue, 29 Jan 2019 10:31:51 -0800 (PST) Received-SPF: pass (google.com: domain of surenb@google.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@google.com header.s=20161025 header.b="J+vXHO/c"; spf=pass (google.com: domain of surenb@google.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=surenb@google.com; dmarc=pass (p=REJECT sp=REJECT dis=NONE) header.from=google.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=0m3skRRv8gGXarJnQx7v/9n5i4k4SmQKxcZwANz4wvY=; b=J+vXHO/cVQyn/1ZJqpK6skQGqPQVpUQSFTHNxOQ/z+6XxcF12Z91kemu2Nn9BKNMUz VP2EBsuvQUqdG6OJx/S2GiAKnWo+P7aQJs+XX8IYSA27JNRhIyd5zPGOuA4KgMsq7Kee QiadlZ0vaoAxeOniQYEFw+UqJTxEOOafgjs+b2yXFkK417Qtr48IV6RG7VIffB2j+Njb c7cVImBJqH3RrxBu4gbUXHt5GgzGTblW6m3mg+uCtQfvUNk0vGUqQKmZ3QJ8lvIbM0cH QoErGjgId+U39N2tUYBt2csNLu2AJeqjLyj3WU/Qlx6fW9iBFyqFB9iWtV5dL84G55L8 HcUw== X-Google-Smtp-Source: AHgI3Ibx6/OVbETdDnoEV80C1606vDQP1T/8S7POacnT0d0ekLrAVuNZHS4p8b+VSew2Gru4p8xK+9b8kamEI0pS2KE= X-Received: by 2002:adf:dc4e:: with SMTP id m14mr7291068wrj.107.1548786711280; Tue, 29 Jan 2019 10:31:51 -0800 (PST) MIME-Version: 1.0 References: <20190124211518.244221-1-surenb@google.com> <20190124211518.244221-6-surenb@google.com> <20190129123843.GK28467@hirez.programming.kicks-ass.net> In-Reply-To: From: Suren Baghdasaryan Date: Tue, 29 Jan 2019 10:31:40 -0800 Message-ID: Subject: Re: [PATCH v3 5/5] psi: introduce psi monitor To: Peter Zijlstra Cc: Greg Kroah-Hartman , Tejun Heo , lizefan@huawei.com, Johannes Weiner , axboe@kernel.dk, dennis@kernel.org, Dennis Zhou , Ingo Molnar , Andrew Morton , Jonathan Corbet , cgroups@vger.kernel.org, linux-mm , linux-doc@vger.kernel.org, LKML , kernel-team@android.com Content-Type: text/plain; charset="UTF-8" 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 Tue, Jan 29, 2019 at 10:18 AM Suren Baghdasaryan wrote: > > On Tue, Jan 29, 2019 at 4:38 AM Peter Zijlstra wrote: > > > > On Thu, Jan 24, 2019 at 01:15:18PM -0800, Suren Baghdasaryan wrote: > > > + atomic_set(&group->polling, polling); > > > + /* > > > + * Memory barrier is needed to order group->polling > > > + * write before times[] read in collect_percpu_times() > > > + */ > > > + smp_mb__after_atomic(); > > > > That's broken, smp_mb__{before,after}_atomic() can only be used on > > atomic RmW operations, something atomic_set() is _not_. > > Oh, I didn't realize that. After reading the following example from > atomic_ops.txt I was under impression that smp_mb__after_atomic() > would make changes done by atomic_set() visible: > > /* All memory operations before this call will > * be globally visible before the clear_bit(). > */ > smp_mb__before_atomic(); > clear_bit( ... ); > /* The clear_bit() will be visible before all > * subsequent memory operations. > */ > smp_mb__after_atomic(); > > but I'm probably missing something. Is there a more detailed > description of these rules anywhere else? I was referred to memory-barriers.txt that explains this clearly stating that "These functions do not imply memory barriers.". Thanks for noticing! Will change to smp_mb(). > Meanwhile I'll change smp_mb__after_atomic() into smp_mb(). Would that > fix the ordering? > > > -- > > You received this message because you are subscribed to the Google Groups "kernel-team" group. > > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. > >