Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759613AbYHHTQF (ORCPT ); Fri, 8 Aug 2008 15:16:05 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754410AbYHHTPy (ORCPT ); Fri, 8 Aug 2008 15:15:54 -0400 Received: from smtp1.linux-foundation.org ([140.211.169.13]:54044 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753040AbYHHTPx (ORCPT ); Fri, 8 Aug 2008 15:15:53 -0400 Date: Fri, 8 Aug 2008 12:14:28 -0700 From: Andrew Morton To: Peter Zijlstra Cc: torvalds@linux-foundation.org, mingo@elte.hu, tglx@linutronix.de, marcin.slusarz@gmail.com, linux-kernel@vger.kernel.org, davem@davemloft.net, rostedt@goodmis.org, paulmck@linux.vnet.ibm.com Subject: Re: [PATCH] printk: robustify printk Message-Id: <20080808121428.646a8b3c.akpm@linux-foundation.org> In-Reply-To: <1218219269.29098.5.camel@lappy.programming.kicks-ass.net> References: <20080324122424.671168000@chello.nl> <1206382547.6437.131.camel@lappy> <20080324115738.85c72bb5.akpm@linux-foundation.org> <1218202249.8625.106.camel@twins> <1218215454.8625.133.camel@twins> <1218217257.29098.2.camel@lappy.programming.kicks-ass.net> <1218219269.29098.5.camel@lappy.programming.kicks-ass.net> X-Mailer: Sylpheed version 2.2.4 (GTK+ 2.8.20; i486-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1051 Lines: 34 On Fri, 08 Aug 2008 20:14:28 +0200 Peter Zijlstra wrote: > void wake_up_klogd(void) > { > - if (!oops_in_progress && waitqueue_active(&log_wait)) > - wake_up_interruptible(&log_wait); > + unsigned long flags; > + struct klogd_wakeup_state *kws; > + > + if (!waitqueue_active(&log_wait)) > + return; > + > + local_irq_save(flags); > + kws = &__get_cpu_var(kws); > + if (!kws->pending) { > + kws->pending = 1; > + call_rcu(&kws->head, __wake_up_klogd); > + } > + local_irq_restore(flags); > } Note that kernel/rcupreempt.c's flavour of call_rcu() takes RCU_DATA_ME().lock, so there are still code sites from which a printk can deadlock. Only now, it is config-dependent. >From a quick look it appears that large amounts of kernel/rcupreempt.c are now a printk-free zone. -- 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/