From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751706AbdITRIs (ORCPT ); Wed, 20 Sep 2017 13:08:48 -0400 Received: from merlin.infradead.org ([205.233.59.134]:48966 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751523AbdITRHS (ORCPT ); Wed, 20 Sep 2017 13:07:18 -0400 Message-Id: <20170920170546.922524234@infradead.org> User-Agent: quilt/0.63-1 Date: Wed, 20 Sep 2017 19:00:20 +0200 From: Peter Zijlstra To: mingo@kernel.org, tglx@linutronix.de Cc: linux-kernel@vger.kernel.org, peterz@infradead.org, rostedt@goodmis.org, bigeasy@linutronix.de, efault@gmx.de, max.byungchul.park@gmail.com Subject: [PATCH 6/7] smp/hotplug: Differentiate the AP-work lockdep class between up and down References: <20170920170014.548896195@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline; filename=peterz-hotplug-4.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org With lockdep-crossrelease we get deadlock reports that span cpu-up and cpu-down chains. Such deadlocks cannot possibly happen because cpu-up and cpu-down are globally serialized. CPU0 CPU1 CPU2 cpuhp_up_callbacks: takedown_cpu: cpuhp_thread_fun: cpuhp_state irq_lock_sparse() irq_lock_sparse() wait_for_completion() cpuhp_state complete() Now that we have consistent AP state, we can trivially separate the AP-work class between up and down using st->bringup. Signed-off-by: Peter Zijlstra (Intel) --- kernel/cpu.c | 41 ++++++++++++++++++++++++++++++++--------- 1 file changed, 32 insertions(+), 9 deletions(-) --- a/kernel/cpu.c +++ b/kernel/cpu.c @@ -68,9 +68,26 @@ struct cpuhp_cpu_state { static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state); #if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP) -static struct lock_class_key cpuhp_state_key; -static struct lockdep_map cpuhp_state_lock_map = - STATIC_LOCKDEP_MAP_INIT("cpuhp_state", &cpuhp_state_key); +static struct lockdep_map cpuhp_state_up_map = + STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map); +static struct lockdep_map cpuhp_state_down_map = + STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map); + + +static void inline cpuhp_lock_acquire(bool bringup) +{ + lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map); +} + +static void inline cpuhp_lock_release(bool bringup) +{ + lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map); +} +#else + +static void inline cpuhp_lock_acquire(bool bringup) { } +static void inline cpuhp_lock_release(bool bringup) { } + #endif /** @@ -512,7 +529,7 @@ static void cpuhp_thread_fun(unsigned in if (WARN_ON_ONCE(!st->should_run)) return; - lock_map_acquire(&cpuhp_state_lock_map); + cpuhp_lock_acquire(bringup); if (st->single) { state = st->cb_state; @@ -564,7 +581,7 @@ static void cpuhp_thread_fun(unsigned in } next: - lock_map_release(&cpuhp_state_lock_map); + cpuhp_lock_release(bringup); if (!st->should_run) complete(&st->done); @@ -581,8 +598,11 @@ cpuhp_invoke_ap_callback(int cpu, enum c if (!cpu_online(cpu)) return 0; - lock_map_acquire(&cpuhp_state_lock_map); - lock_map_release(&cpuhp_state_lock_map); + cpuhp_lock_acquire(false); + cpuhp_lock_release(false); + + cpuhp_lock_acquire(true); + cpuhp_lock_release(true); /* * If we are up and running, use the hotplug thread. For early calls @@ -620,8 +640,11 @@ static int cpuhp_kick_ap_work(unsigned i enum cpuhp_state prev_state = st->state; int ret; - lock_map_acquire(&cpuhp_state_lock_map); - lock_map_release(&cpuhp_state_lock_map); + cpuhp_lock_acquire(false); + cpuhp_lock_release(false); + + cpuhp_lock_acquire(true); + cpuhp_lock_release(true); trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work); ret = cpuhp_kick_ap(st, st->target);