Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1758548AbZJHP0X (ORCPT ); Thu, 8 Oct 2009 11:26:23 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1758459AbZJHP0X (ORCPT ); Thu, 8 Oct 2009 11:26:23 -0400 Received: from smtp-out003.kontent.com ([81.88.40.217]:38830 "EHLO smtp-out003.kontent.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758439AbZJHP0W convert rfc822-to-8bit (ORCPT ); Thu, 8 Oct 2009 11:26:22 -0400 From: Oliver Neukum To: Alan Stern Subject: Re: [PATCH 4/5] usb_serial: Kill port mutex Date: Thu, 8 Oct 2009 17:27:11 +0200 User-Agent: KMail/1.10.3 (Linux/2.6.31-rc9-0.1-default; KDE/4.1.3; x86_64; ; ) Cc: Alan Cox , Greg KH , Kernel development list , USB list References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 8BIT Content-Disposition: inline Message-Id: <200910081727.11745.oliver@neukum.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1430 Lines: 38 Am Donnerstag, 8. Oktober 2009 16:58:39 schrieb Alan Stern: > On Thu, 8 Oct 2009, Oliver Neukum wrote: > > Am Mittwoch, 7. Oktober 2009 23:34:12 schrieb Alan Stern: > > > Other schemes could work, but to me it seems simplest to rely on a flag > > > protected by a spinlock. ?The flag would mean "URBs are supposed to be > > > queued unless we are suspended". ?It would be set by open and > > > unthrottle, and cleared by close and throttle. > > > > 1. Why a spinlock? > > Because the amount of work involved seems too small for a mutex. But > you could use a mutex if you wanted, since everything occurs in process > context. We have to submit URBs under that lock. > > 2. Can we get by with only one flag? > > If all you want to do is answer a single question ("Should URBs be > submitted") then a single flag should be all you need. Why, do you > think more information will be necessary? You can always add more. We have at least three reasons URBs should not be submitted. - closure - throttling - suspension Resume() should not submit if either closure or throttling are active, neither should unthrottle() resubmit if closure or suspension are active. Regards Oliver -- 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/