Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932280Ab2JVXMg (ORCPT ); Mon, 22 Oct 2012 19:12:36 -0400 Received: from mail-ee0-f46.google.com ([74.125.83.46]:37326 "EHLO mail-ee0-f46.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753307Ab2JVXMf (ORCPT ); Mon, 22 Oct 2012 19:12:35 -0400 MIME-Version: 1.0 In-Reply-To: <1350944894.19698.208.camel@doorstop.aus.2wire.com> References: <1350944894.19698.208.camel@doorstop.aus.2wire.com> From: Bryan Wu Date: Mon, 22 Oct 2012 16:12:13 -0700 Message-ID: Subject: Re: [PATCH] ledtrig-cpu: use spin_lock to replace mutex lock To: Nathan Lynch Cc: "Rafael J. Wysocki" , Miles Lane , akpm , Linux LED Subsystem , Linus Walleij , lkml Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1514 Lines: 40 On Mon, Oct 22, 2012 at 3:28 PM, Nathan Lynch wrote: > Hi Bryan, > > On Thu, 2012-10-18 at 11:18 -0700, Bryan Wu wrote: >> @@ -117,14 +117,14 @@ static int __init ledtrig_cpu_init(void) >> for_each_possible_cpu(cpu) { >> struct led_trigger_cpu *trig = &per_cpu(cpu_trig, cpu); >> >> - mutex_init(&trig->lock); >> + spin_lock_init(&trig->lock); >> >> snprintf(trig->name, MAX_NAME_LEN, "cpu%d", cpu); >> >> - mutex_lock(&trig->lock); >> + spin_lock(&trig->lock); >> led_trigger_register_simple(trig->name, &trig->_trig); >> trig->lock_is_inited = 1; >> - mutex_unlock(&trig->lock); >> + spin_unlock(&trig->lock); > > I wouldn't know how to fix the original problem, but I don't think this > patch is okay -- led_trigger_register_simple() does things that > potentially sleep (GFP_KERNEL allocation, down_write), so it's not safe > to call while holding a spinlock. > Looks like we got a hard issue, since led_trigger_register() families and even led_trigger_event() might use rwsem for locking, these are all potentially sleep, which are not easy to modified for atomic context. Any hints are welcome. Thanks, -Bryan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/