From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-yw0-x242.google.com (mail-yw0-x242.google.com [IPv6:2607:f8b0:4002:c05::242]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 3rYsKP1jn8zDq5c for ; Wed, 22 Jun 2016 01:36:57 +1000 (AEST) Received: by mail-yw0-x242.google.com with SMTP id i12so2187793ywa.0 for ; Tue, 21 Jun 2016 08:36:57 -0700 (PDT) Date: Tue, 21 Jun 2016 11:36:51 -0400 From: Tejun Heo To: Gautham R Shenoy Cc: Peter Zijlstra , Thomas Gleixner , Michael Ellerman , Abdul Haleem , Aneesh Kumar , linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, kernel-team@fb.com Subject: Re: [PATCH 1/2] workqueue: Move wq_update_unbound_numa() to the beginning of CPU_ONLINE Message-ID: <20160621153651.GF3262@mtj.duckdns.org> References: <6b3c7059ec5d2d6157d23d619e4507692a42a5bd.1465311052.git.ego@linux.vnet.ibm.com> <20160615155350.GB24102@mtj.duckdns.org> <20160615192844.GA20301@in.ibm.com> <20160616193504.GB3262@mtj.duckdns.org> <20160621141231.GA30251@in.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20160621141231.GA30251@in.ibm.com> List-Id: Linux on PowerPC Developers Mail List List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Tue, Jun 21, 2016 at 07:42:31PM +0530, Gautham R Shenoy wrote: > > Subject: [PATCH] sched: allow kthreads to fallback to online && !active cpus > > > > During CPU hotplug, CPU_ONLINE callbacks are run while the CPU is > > online but not active. A CPU_ONLINE callback may create or bind a > > kthread so that its cpus_allowed mask only allows the CPU which is > > being brought online. The kthread may start executing before the CPU > > is made active and can end up in select_fallback_rq(). > > > > In such cases, the expected behavior is selecting the CPU which is > > coming online; however, because select_fallback_rq() only chooses from > > active CPUs, it determines that the task doesn't have any viable CPU > > in its allowed mask and ends up overriding it to cpu_possible_mask. > > > > CPU_ONLINE callbacks should be able to put kthreads on the CPU which > > is coming online. Update select_fallback_rq() so that it follows > > cpu_online() rather than cpu_active() for kthreads. > > > > Signed-off-by: Tejun Heo > > Reported-by: Gautham R Shenoy > > Hi Tejun, > > This patch fixes the issue on POWER. I am able to see the worker > threads of the unbound workqueues of the newly onlined node with this. > > Tested-by: Gautham R. Shenoy Peter? -- tejun