From patchwork Fri Feb 26 10:20:12 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Luis Henriques X-Patchwork-Id: 589054 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from huckleberry.canonical.com (huckleberry.canonical.com [91.189.94.19]) by ozlabs.org (Postfix) with ESMTP id 5D343140BB2; Sat, 27 Feb 2016 01:35:56 +1100 (AEDT) Received: from localhost ([127.0.0.1] helo=huckleberry.canonical.com) by huckleberry.canonical.com with esmtp (Exim 4.76) (envelope-from ) id 1aZJUk-0002mj-8p; Fri, 26 Feb 2016 14:35:50 +0000 Received: from youngberry.canonical.com ([91.189.89.112]) by huckleberry.canonical.com with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.76) (envelope-from ) id 1aZFXM-0008CV-IT for kernel-team@lists.ubuntu.com; Fri, 26 Feb 2016 10:22:16 +0000 Received: from av-217-129-142-138.netvisao.pt ([217.129.142.138] helo=localhost) by youngberry.canonical.com with esmtpsa (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.76) (envelope-from ) id 1aZFXL-0006Hp-Ro; Fri, 26 Feb 2016 10:22:16 +0000 From: Luis Henriques To: linux-kernel@vger.kernel.org, stable@vger.kernel.org, kernel-team@lists.ubuntu.com Subject: [PATCH 3.16.y-ckt 041/129] vmstat: explicitly schedule per-cpu work on the CPU we need it to run on Date: Fri, 26 Feb 2016 10:20:12 +0000 Message-Id: <1456482100-4667-42-git-send-email-luis.henriques@canonical.com> In-Reply-To: <1456482100-4667-1-git-send-email-luis.henriques@canonical.com> References: <1456482100-4667-1-git-send-email-luis.henriques@canonical.com> X-Extended-Stable: 3.16 X-Mailman-Approved-At: Fri, 26 Feb 2016 14:35:48 +0000 Cc: Michal Hocko , Jiri Slaby , Kamal Mostafa , Tejun Heo , Mike Galbraith , Christoph Lameter , Linus Torvalds X-BeenThere: kernel-team@lists.ubuntu.com X-Mailman-Version: 2.1.14 Precedence: list List-Id: Kernel team discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , MIME-Version: 1.0 Errors-To: kernel-team-bounces@lists.ubuntu.com Sender: kernel-team-bounces@lists.ubuntu.com 3.16.7-ckt25 -stable review patch. If anyone has any objections, please let me know. ---8<------------------------------------------------------------ From: Linus Torvalds commit 176bed1de5bf977938cad26551969eca8f0883b1 upstream. The vmstat code uses "schedule_delayed_work_on()" to do the initial startup of the delayed work on the right CPU, but then once it was started it would use the non-cpu-specific "schedule_delayed_work()" to re-schedule it on that CPU. That just happened to schedule it on the same CPU historically (well, in almost all situations), but the code _requires_ this work to be per-cpu, and should say so explicitly rather than depend on the non-cpu-specific scheduling to schedule on the current CPU. The timer code is being changed to not be as single-minded in always running things on the calling CPU. See also commit 874bbfe600a6 ("workqueue: make sure delayed work run in local cpu") that for now maintains the local CPU guarantees just in case there are other broken users that depended on the accidental behavior. js: 3.12 backport Cc: Christoph Lameter Cc: Tejun Heo Cc: Mike Galbraith Cc: Michal Hocko Signed-off-by: Linus Torvalds Signed-off-by: Jiri Slaby [ kamal: backport to 3.16-stable: use queue_delayed_work_on() ] Signed-off-by: Kamal Mostafa Signed-off-by: Luis Henriques --- mm/vmstat.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/mm/vmstat.c b/mm/vmstat.c index 038f9418b234..8c0c76083562 100644 --- a/mm/vmstat.c +++ b/mm/vmstat.c @@ -1233,7 +1233,8 @@ int sysctl_stat_interval __read_mostly = HZ; static void vmstat_update(struct work_struct *w) { refresh_cpu_vm_stats(); - queue_delayed_work(vmstat_wq, this_cpu_ptr(&vmstat_work), + queue_delayed_work_on(smp_processor_id(), vmstat_wq, + this_cpu_ptr(&vmstat_work), round_jiffies_relative(sysctl_stat_interval)); }