From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934255AbZGQImQ (ORCPT ); Fri, 17 Jul 2009 04:42:16 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S934239AbZGQImQ (ORCPT ); Fri, 17 Jul 2009 04:42:16 -0400 Received: from nwd2mail10.analog.com ([137.71.25.55]:57171 "EHLO nwd2mail10.analog.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S934228AbZGQImP (ORCPT ); Fri, 17 Jul 2009 04:42:15 -0400 X-IronPort-AV: E=Sophos;i="4.42,416,1243828800"; d="scan'208";a="1672352" From: Barry Song <21cnbao@gmail.com> To: mingo@redhat.com, dahlmann.thomas@arcor.de CC: linux-kernel@vger.kernel.org, uclinux-dist-devel@blackfin.uclinux.org, Barry Song <21cnbao@gmail.com> Subject: [PATCH] Delete redundant IRQ_DISABLED check in irq_thread Date: Fri, 17 Jul 2009 16:43:49 +0800 Message-ID: <1247820229-4983-1-git-send-email-21cnbao@gmail.com> X-Mailer: git-send-email 1.5.6.3 MIME-Version: 1.0 Content-Type: text/plain Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Signed-off-by: Barry Song <21cnbao@gmail.com> I think it is completely redundant to check IRQ_DISABLED to decide whether thread_fn will be called. At first, the irq_thread is waken up by HARDIRQ handler, if IRQ_DISABLED is true, HARDIRQ will have no chance to run, then irq_thread will not run. So there is only a situation that both HARDIRQ can run and IRQ_DISABLED is set. The case is that the flag is set in the interval of HARDIRQ enter and irq_thread is scheduled to run. I think there is nobody which is interested to disable irq in the interval except HARDIRQ handler itself. Then that causes the second problem I will explain. Secondly, checking the flag causes some problems in fact. We often call disable_irq_nosync to diable irq in HARDIRQ to avoid flooding irq to follow. But the disable_irq_nosync will set IRQ_DISABLED flag, then that will prevent the execution of thread_fn. That's not the original idea to call disable_irq_nosync in HARDIRQ. So I guess deleting the check is maybe better and more compact. -Barry --- kernel/irq/manage.c | 17 +---------------- 1 files changed, 1 insertions(+), 16 deletions(-) diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c index 50da676..ff4e05d 100644 --- a/kernel/irq/manage.c +++ b/kernel/irq/manage.c @@ -460,22 +460,7 @@ static int irq_thread(void *data) atomic_inc(&desc->threads_active); - spin_lock_irq(&desc->lock); - if (unlikely(desc->status & IRQ_DISABLED)) { - /* - * CHECKME: We might need a dedicated - * IRQ_THREAD_PENDING flag here, which - * retriggers the thread in check_irq_resend() - * but AFAICT IRQ_PENDING should be fine as it - * retriggers the interrupt itself --- tglx - */ - desc->status |= IRQ_PENDING; - spin_unlock_irq(&desc->lock); - } else { - spin_unlock_irq(&desc->lock); - - action->thread_fn(action->irq, action->dev_id); - } + action->thread_fn(action->irq, action->dev_id); wake = atomic_dec_and_test(&desc->threads_active); -- 1.5.6.3