From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751531AbcFXJBR (ORCPT ); Fri, 24 Jun 2016 05:01:17 -0400 Received: from terminus.zytor.com ([198.137.202.10]:44196 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750972AbcFXJBP (ORCPT ); Fri, 24 Jun 2016 05:01:15 -0400 Date: Fri, 24 Jun 2016 02:00:32 -0700 From: tip-bot for Tejun Heo Message-ID: Cc: htejun@gmail.com, ego@linux.vnet.ibm.com, peterz@infradead.org, tglx@linutronix.de, tj@kernel.org, torvalds@linux-foundation.org, mpe@ellerman.id.au, linux-kernel@vger.kernel.org, aneesh.kumar@linux.vnet.ibm.com, abdhalee@linux.vnet.ibm.com, mingo@kernel.org, hpa@zytor.com Reply-To: hpa@zytor.com, mingo@kernel.org, aneesh.kumar@linux.vnet.ibm.com, mpe@ellerman.id.au, linux-kernel@vger.kernel.org, abdhalee@linux.vnet.ibm.com, tj@kernel.org, torvalds@linux-foundation.org, htejun@gmail.com, tglx@linutronix.de, peterz@infradead.org, ego@linux.vnet.ibm.com In-Reply-To: <20160616193504.GB3262@mtj.duckdns.org> References: <20160616193504.GB3262@mtj.duckdns.org> To: linux-tip-commits@vger.kernel.org Subject: [tip:sched/urgent] sched/core: Allow kthreads to fall back to online && !active cpus Git-Commit-ID: feb245e304f343cf5e4f9123db36354144dce8a4 X-Mailer: tip-git-log-daemon Robot-ID: Robot-Unsubscribe: Contact to get blacklisted from these emails MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: feb245e304f343cf5e4f9123db36354144dce8a4 Gitweb: http://git.kernel.org/tip/feb245e304f343cf5e4f9123db36354144dce8a4 Author: Tejun Heo AuthorDate: Thu, 16 Jun 2016 15:35:04 -0400 Committer: Ingo Molnar CommitDate: Fri, 24 Jun 2016 08:26:53 +0200 sched/core: Allow kthreads to fall back 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. Reported-by: Gautham R Shenoy Tested-by: Gautham R. Shenoy Signed-off-by: Tejun Heo Signed-off-by: Peter Zijlstra (Intel) Cc: Abdul Haleem Cc: Aneesh Kumar Cc: Linus Torvalds Cc: Michael Ellerman Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: kernel-team@fb.com Cc: linuxppc-dev@lists.ozlabs.org Link: http://lkml.kernel.org/r/20160616193504.GB3262@mtj.duckdns.org Signed-off-by: Ingo Molnar --- kernel/sched/core.c | 4 +++- 1 file changed, 3 insertions(+), 1 deletion(-) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 4135ac8..51d7105 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1536,7 +1536,9 @@ static int select_fallback_rq(int cpu, struct task_struct *p) for (;;) { /* Any allowed, online CPU? */ for_each_cpu(dest_cpu, tsk_cpus_allowed(p)) { - if (!cpu_active(dest_cpu)) + if (!(p->flags & PF_KTHREAD) && !cpu_active(dest_cpu)) + continue; + if (!cpu_online(dest_cpu)) continue; goto out; }