From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932689AbdDRKf2 (ORCPT ); Tue, 18 Apr 2017 06:35:28 -0400 Received: from merlin.infradead.org ([205.233.59.134]:40140 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932584AbdDRKfX (ORCPT ); Tue, 18 Apr 2017 06:35:23 -0400 Message-Id: <20170418103422.687248115@infradead.org> User-Agent: quilt/0.63-1 Date: Tue, 18 Apr 2017 12:32:16 +0200 From: Peter Zijlstra To: jbaron@akamai.com, rostedt@goodmis.org, tglx@linutronix.de, mingo@kernel.org, bigeasy@linutronix.de, peterz@infradead.org Cc: linux-kernel@vger.kernel.org Subject: [PATCH 3/3] perf: Avoid cpu_hotplug_lock r-r recursion References: <20170418103213.089888286@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline; filename=peterz-perf-fix-hp-fail.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org There are two call-sites where using static_key results in recursing on the cpu_hotplug_lock. Signed-off-by: Peter Zijlstra (Intel) --- kernel/events/core.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -7785,7 +7785,7 @@ static int perf_swevent_init(struct perf if (err) return err; - static_key_slow_inc(&perf_swevent_enabled[event_id]); + static_key_slow_inc_nohp(&perf_swevent_enabled[event_id]); event->destroy = sw_perf_event_destroy; } @@ -9294,7 +9294,7 @@ static void account_event(struct perf_ev mutex_lock(&perf_sched_mutex); if (!atomic_read(&perf_sched_count)) { - static_branch_enable(&perf_sched_events); + static_key_slow_inc_nohp(&perf_sched_events.key); /* * Guarantee that all CPUs observe they key change and * call the perf scheduling hooks before proceeding to