From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758337Ab2CAKzM (ORCPT ); Thu, 1 Mar 2012 05:55:12 -0500 Received: from mail-we0-f174.google.com ([74.125.82.174]:64821 "EHLO mail-we0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754767Ab2CAKyx (ORCPT ); Thu, 1 Mar 2012 05:54:53 -0500 Authentication-Results: mr.google.com; spf=pass (google.com: domain of ido@wizery.com designates 10.180.107.169 as permitted sender) smtp.mail=ido@wizery.com Date: Thu, 1 Mar 2012 12:54:47 +0200 From: Ido Yariv To: Thomas Gleixner Cc: linux-kernel@vger.kernel.org Subject: Re: [RFC] genirq: Flush the irq thread on synchronization Message-ID: <20120301105447.GB1566@WorkStation> References: <1322843052-7166-1-git-send-email-ido@wizery.com> <20111204190932.GO32400@WorkStation> <20111216104828.GB18877@WorkStation> <20120213094329.GA29428@WorkStation> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Thomas, On Wed, Feb 15, 2012 at 03:34:11PM +0100, Thomas Gleixner wrote: > On Mon, 13 Feb 2012, Ido Yariv wrote: > > > Hi Thomas, > > > > On Sun, Dec 04, 2011 at 09:09:32PM +0200, Ido Yariv wrote: > > > Hi Thomas, > > > > > > On Sat, Dec 03, 2011 at 12:21:46AM +0100, Thomas Gleixner wrote: > > > > I can see your problem, but this might lead to threads_active leaks > > > > under certain conditions. desc->threads_active was only meant to deal > > > > with shared interrupts. > > > > > > > > We explicitely allow a design where the primary handler can leave the > > > > device interrupt enabled and allow further interrupts to occur while > > > > the handler is running. We only have a single bit to note that the > > > > thread should run, but your wakeup would up the threads_active count > > > > in that scenario several times w/o a counterpart which decrements it. > > > > > > > > The solution for this is to keep the current threads_active semantics > > > > and make the wait function different. Instead of waiting for > > > > threads_active to become 0 it should wait for threads_active == 0 and > > > > the IRQTF_RUNTHREAD for all actions to be cleared. To avoid looping > > > > over the actions, we can take a similar approach as we take with the > > > > desc->threads_oneshot bitfield. > > > > > > Thanks for reviewing this. > > > > > > I might be missing something, but I don't see any potential > > > threads_active leaks in this approach. We wont increase threads_active > > > if IRQTF_RUNTHREAD was already set beforehand (as test_and_set_bit() > > > will return 1). > > > > > > If irq_wake_thread is called multiple times before irq_thread has had a > > > chance to run, threads_active will only be increased once and decreased > > > back when IRQTF_RUNTHREAD is cleared. > > > > > > Am I missing something? If not, do you see any other issues with this > > > implementation? > > > > Any thoughts on this? > > Sorry, went of my radar. Will have a look later today. Have you had a chance to look into this? Thanks, Ido.