Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755581AbYGaGHB (ORCPT ); Thu, 31 Jul 2008 02:07:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752299AbYGaGGw (ORCPT ); Thu, 31 Jul 2008 02:06:52 -0400 Received: from casper.infradead.org ([85.118.1.10]:49246 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752205AbYGaGGv (ORCPT ); Thu, 31 Jul 2008 02:06:51 -0400 Subject: Re: [PATCH] Fix Bug messages From: Peter Zijlstra To: Chirag Jog Cc: J?rgen Mell , Thomas Gleixner , LKML , rt-users , Steven Rostedt , Clark Williams , Josh Triplett , "Timothy R. Chavez" In-Reply-To: <20080730171842.GB3420@linux.vnet.ibm.com> References: <200807301101.32417.j.mell@t-online.de> <20080730171842.GB3420@linux.vnet.ibm.com> Content-Type: text/plain; charset=utf-8 Date: Thu, 31 Jul 2008 08:06:42 +0200 Message-Id: <1217484402.8157.73.camel@twins> Mime-Version: 1.0 X-Mailer: Evolution 2.22.3.1 Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 5159 Lines: 159 On Wed, 2008-07-30 at 22:48 +0530, Chirag Jog wrote: > * J?rgen Mell [2008-07-30 11:01:32]: > > > Hello Thomas, > > > > On Wednesday, 30. July 2008, Thomas Gleixner wrote: > > > We are pleased to announce the 2.6.26-rt1 tree, which can be > > > downloaded from the location: > > > > I have tried the new kernel and have some good news and some bad news: > > > > The good news: The machine boots and seems to run without major problems. > > > > The bad news: It produces continuously lots of bug messages in the error > > logs (cf. attached dmesg.tgz). The error at rtmutex.c:743 was already > > present in 2.6.25-rt* when ACPI was enabled. The 'using smp_processor_id > > () in preemptible code' is new here with 2.6.26. > > > > Machine is an old Athlon XP (single core) on an EPOX mainboard with VIA > > chipset. > > > > If I can help with testing, please let me know. > > > > Bye, > > Jürgen > > > > > This patch should solve some of the bug messages. > It does two things: > 1. Change rt_runtime_lock to be a raw spinlock as the comment above it > says: it is nested inside the rq lock. > > 2. Change mnt_writers to be a per_cpu locked variable. > This eliminates the need for the codepath to disable preemption and > then potentially sleep, leading to the BUG messages Looks sane, thanks Chirag! > Signed-Off-By: Chirag > > > > Index: linux-2.6.26-rt1/kernel/sched.c > =================================================================== > --- linux-2.6.26-rt1.orig/kernel/sched.c 2008-07-30 22:37:19.000000000 +0530 > +++ linux-2.6.26-rt1/kernel/sched.c 2008-07-30 22:37:24.000000000 +0530 > @@ -208,7 +208,7 @@ > > struct rt_bandwidth { > /* nests inside the rq lock: */ > - spinlock_t rt_runtime_lock; > + raw_spinlock_t rt_runtime_lock; > ktime_t rt_period; > u64 rt_runtime; > struct hrtimer rt_period_timer; > @@ -472,7 +472,7 @@ > u64 rt_time; > u64 rt_runtime; > /* Nests inside the rq lock: */ > - spinlock_t rt_runtime_lock; > + raw_spinlock_t rt_runtime_lock; > > #ifdef CONFIG_RT_GROUP_SCHED > unsigned long rt_nr_boosted; > Index: linux-2.6.26-rt1/fs/namespace.c > =================================================================== > --- linux-2.6.26-rt1.orig/fs/namespace.c 2008-07-30 22:39:30.000000000 +0530 > +++ linux-2.6.26-rt1/fs/namespace.c 2008-07-30 22:39:36.000000000 +0530 > @@ -178,13 +178,13 @@ > unsigned long count; > struct vfsmount *mnt; > } ____cacheline_aligned_in_smp; > -static DEFINE_PER_CPU(struct mnt_writer, mnt_writers); > +static DEFINE_PER_CPU_LOCKED(struct mnt_writer, mnt_writers); > > static int __init init_mnt_writers(void) > { > int cpu; > for_each_possible_cpu(cpu) { > - struct mnt_writer *writer = &per_cpu(mnt_writers, cpu); > + struct mnt_writer *writer = &per_cpu_var_locked(mnt_writers, cpu); > spin_lock_init(&writer->lock); > lockdep_set_class(&writer->lock, &writer->lock_class); > writer->count = 0; > @@ -199,7 +199,7 @@ > struct mnt_writer *cpu_writer; > > for_each_possible_cpu(cpu) { > - cpu_writer = &per_cpu(mnt_writers, cpu); > + cpu_writer = &per_cpu_var_locked(mnt_writers, cpu); > spin_unlock(&cpu_writer->lock); > } > } > @@ -251,8 +251,8 @@ > { > int ret = 0; > struct mnt_writer *cpu_writer; > - > - cpu_writer = &get_cpu_var(mnt_writers); > + int cpu = 0; > + cpu_writer = &get_cpu_var_locked(mnt_writers, &cpu); > spin_lock(&cpu_writer->lock); > if (__mnt_is_readonly(mnt)) { > ret = -EROFS; > @@ -262,7 +262,7 @@ > cpu_writer->count++; > out: > spin_unlock(&cpu_writer->lock); > - put_cpu_var(mnt_writers); > + put_cpu_var_locked(mnt_writers, cpu); > return ret; > } > EXPORT_SYMBOL_GPL(mnt_want_write); > @@ -273,7 +273,7 @@ > struct mnt_writer *cpu_writer; > > for_each_possible_cpu(cpu) { > - cpu_writer = &per_cpu(mnt_writers, cpu); > + cpu_writer = &per_cpu_var_locked(mnt_writers, cpu); > spin_lock(&cpu_writer->lock); > __clear_mnt_count(cpu_writer); > cpu_writer->mnt = NULL; > @@ -332,8 +332,8 @@ > { > int must_check_underflow = 0; > struct mnt_writer *cpu_writer; > - > - cpu_writer = &get_cpu_var(mnt_writers); > + int cpu = 0; > + cpu_writer = &get_cpu_var_locked(mnt_writers, &cpu); > spin_lock(&cpu_writer->lock); > > use_cpu_writer_for_mount(cpu_writer, mnt); > @@ -360,7 +360,7 @@ > * __mnt_writers can underflow. Without it, > * we could theoretically wrap __mnt_writers. > */ > - put_cpu_var(mnt_writers); > + put_cpu_var_locked(mnt_writers, cpu); > } > EXPORT_SYMBOL_GPL(mnt_drop_write); > > @@ -612,7 +612,7 @@ > * can come in. > */ > for_each_possible_cpu(cpu) { > - struct mnt_writer *cpu_writer = &per_cpu(mnt_writers, cpu); > + struct mnt_writer *cpu_writer = &per_cpu_var_locked(mnt_writers, cpu); > if (cpu_writer->mnt != mnt) > continue; > spin_lock(&cpu_writer->lock); > > -- 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/