Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1761299AbWLIACl (ORCPT ); Fri, 8 Dec 2006 19:02:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1947549AbWLIACI (ORCPT ); Fri, 8 Dec 2006 19:02:08 -0500 Received: from 216-99-217-87.dsl.aracnet.com ([216.99.217.87]:37656 "EHLO sous-sol.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1947540AbWLIABu (ORCPT ); Fri, 8 Dec 2006 19:01:50 -0500 Message-Id: <20061209000303.850378000@sous-sol.org> References: <20061208235751.890503000@sous-sol.org> User-Agent: quilt/0.45-1 Date: Fri, 08 Dec 2006 15:58:20 -0800 From: Chris Wright To: linux-kernel@vger.kernel.org, stable@kernel.org, torvalds@osdl.org Cc: Justin Forbes , Zwane Mwaikambo , "Theodore Ts'o" , Randy Dunlap , Dave Jones , Chuck Wolber , Chris Wedgwood , Michael Krufky , akpm@osdl.org, alan@lxorguk.ukuu.org.uk, zach@vmware.com, mingo@elte.hu, caglar@pardus.org.tr Subject: [patch 29/32] softirq: remove BUG_ONs which can incorrectly trigger Content-Disposition: inline; filename=softirq-remove-bug_ons-which-can-incorrectly-trigger.patch Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2067 Lines: 51 -stable review patch. If anyone has any objections, please let us know. ------------------ From: Zachary Amsden It is possible to have tasklets get scheduled before softirqd has had a chance to spawn on all CPUs. This is totally harmless; after success during action CPU_UP_PREPARE, action CPU_ONLINE will be called, which immediately wakes softirqd on the appropriate CPU to process the already pending tasklets. So there is no danger of having a missed wakeup for any tasklets that were already pending. In particular, i386 is affected by this during startup, and is visible when using a very large initrd; during the time it takes for the initrd to be decompressed, a timer IRQ can come in and schedule RCU callbacks. It is also possible that resending of a hardware IRQ via a softirq triggers the same bug. Because of different timing conditions, this shows up in all emulators and virtual machines tested, including Xen, VMware, Virtual PC, and Qemu. It is also possible to trigger on native hardware with a large enough initrd, although I don't have a reliable case demonstrating that. Signed-off-by: Zachary Amsden Cc: Cc: Ingo Molnar Cc: Signed-off-by: Andrew Morton Signed-off-by: Chris Wright --- kernel/softirq.c | 2 -- 1 file changed, 2 deletions(-) --- linux-2.6.19.orig/kernel/softirq.c +++ linux-2.6.19/kernel/softirq.c @@ -574,8 +574,6 @@ static int __cpuinit cpu_callback(struct switch (action) { case CPU_UP_PREPARE: - BUG_ON(per_cpu(tasklet_vec, hotcpu).list); - BUG_ON(per_cpu(tasklet_hi_vec, hotcpu).list); p = kthread_create(ksoftirqd, hcpu, "ksoftirqd/%d", hotcpu); if (IS_ERR(p)) { printk("ksoftirqd for %i failed\n", hotcpu); -- - 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/