From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932437AbXDEAip (ORCPT ); Wed, 4 Apr 2007 20:38:45 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S932433AbXDEAiY (ORCPT ); Wed, 4 Apr 2007 20:38:24 -0400 Received: from [198.99.130.12] ([198.99.130.12]:50394 "EHLO saraswathi.solana.com" rhost-flags-FAIL-FAIL-OK-OK) by vger.kernel.org with ESMTP id S932424AbXDEAiV (ORCPT ); Wed, 4 Apr 2007 20:38:21 -0400 Date: Wed, 4 Apr 2007 20:34:03 -0400 From: Jeff Dike To: Andrew Morton Cc: LKML , uml-devel Subject: [ PATCH 4/4] UML - irq locking commentary Message-ID: <20070405003403.GA13285@c2.user-mode-linux.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.4.2.2i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Locking commentary. Signed-off-by: Jeff Dike -- arch/um/kernel/irq.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) Index: linux-2.6.21-mm/arch/um/kernel/irq.c =================================================================== --- linux-2.6.21-mm.orig/arch/um/kernel/irq.c 2007-04-02 13:04:27.000000000 -0400 +++ linux-2.6.21-mm/arch/um/kernel/irq.c 2007-04-02 14:48:48.000000000 -0400 @@ -78,6 +78,14 @@ skip: return 0; } +/* + * This list is accessed under irq_lock, except in sigio_handler, + * where it is safe from being modified. IRQ handlers won't change it - + * if an IRQ source has vanished, it will be freed by free_irqs just + * before returning from sigio_handler. That will process a separate + * list of irqs to free, with its own locking, coming back here to + * remove list elements, taking the irq_lock to do so. + */ static struct irq_fd *active_fds = NULL; static struct irq_fd **last_irq_ptr = &active_fds; @@ -243,6 +251,7 @@ void free_irq_by_fd(int fd) free_irq_by_cb(same_fd, &fd); } +/* Must be called with irq_lock held */ static struct irq_fd *find_irq_by_fd(int fd, int irqnum, int *index_out) { struct irq_fd *irq; @@ -308,6 +317,12 @@ void deactivate_fd(int fd, int irqnum) ignore_sigio_fd(fd); } +/* + * Called just before shutdown in order to provide a clean exec + * environment in case the system is rebooting. No locking because + * that would cause a pointless shutdown hang if something hadn't + * released the lock. + */ int deactivate_all_fds(void) { struct irq_fd *irq;