linux-kernel - Re: 2.6.26.3-rt2

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Date:	Thu, 21 Aug 2008 22:00:58 +0200
From:	"John Kacur" <jkacur@...il.com>
To:	"Steven Rostedt" <rostedt@...dmis.org>
Cc:	LKML <linux-kernel@...r.kernel.org>,
	RT <linux-rt-users@...r.kernel.org>,
	"Ingo Molnar" <mingo@...e.hu>,
	"Thomas Gleixner" <tglx@...utronix.de>,
	"Chirag Jog" <chirag@...ux.vnet.ibm.com>,
	"Peter Zijlstra" <peterz@...radead.org>
Subject: Re: 2.6.26.3-rt2

On Thu, Aug 21, 2008 at 9:33 PM, John Kacur <jkacur@...il.com> wrote:
> On Thu, Aug 21, 2008 at 7:18 PM, Steven Rostedt <rostedt@...dmis.org> wrote:
>> We are pleased to announce the 2.6.26.3-rt2 tree, which can be
>> downloaded from the location:
>>
>>  http://rt.et.redhat.com/download/
>>
>> Information on the RT patch can be found at:
>>
>>  http://rt.wiki.kernel.org/index.php/Main_Page
>>
>> Changes since 2.6.26-rt1
>>
>>  - ported to 2.6.26.3
>>
>>  - basic compile fixes (Steven Rostedt)
>>
>>  - basic raw lock conversions (Steven Rostedt)
>>
>>  - powerpc: irq radix tree updates (Sebastien Dugue)
>>
>>  - call_rcu_sched (Paul E. McKenney)
>>
>>  - rcu trace preemption fixes (Paul E. Mckenney)
>>
>>  - remove lock in pm_qos_requirement (John Kacur)
>>
>>  - rcu_process_callbacks (Paul E. McKenney)
>>
>>  - rcu memory barriers update (Paul E. McKenney)
>>
>>  - shorten posix_cpu_timers thread names (Arnaldo Carvalho de Melo)
>>
>>  - account IRQ and RT load in SCHED_OTHER (Peter Zijlstra)
>>
>>  - seq_lock updates/fixes (Gregory Haskins)
>>
>> to build a 2.6.26.3-rt2 tree, the following patches should be applied:
>>
>>  http://www.kernel.org/pub/linux/kernel/v2.6/linux-2.6.26.tar.bz2
>>  http://kernel.org/pub/linux/kernel/v2.6/patch-2.6.26.3.bz2
>>  http://rt.et.redhat.com/download/patch-2.6.26.3-rt2.bz2
>>
>>
>>
>> And like always, my RT version of Matt Mackall's ketchup will get this
>> for you nicely:
>>
>>  http://people.redhat.com/srostedt/rt/tools/ketchup-0.9.8-rt3
>>
>>
>> The broken out patches are also available.
>>
>
> Hi Steve
>
> Probably one of the most important patches that was missed is the one
> from Chirag. I've taken it and updated it against 2.6.26.3-rt2 for
> you, in case that will speed up -rt3 (see attached). (two hunks were
> rejected because another applied fix fixed the same thing as part of
> Chirag's patch.
>
> I've compiled and done some limited testing, and among other things it
> removes this kind of message.
> BUG: sleeping function called from invalid context hald-runner(12244)
> at kernel/rtmutex.c:743
> in_atomic():1 [00000001], irqs_disabled():0
> Pid: 12244, comm: hald-runner Tainted: G        W 2.6.26.3-rt2 #1
>
> Call Trace:
>  [<ffffffff802d3cda>] ? mnt_want_write+0x19/0xbc
>  [<ffffffff802307b6>] __might_sleep+0x12d/0x132
>  [<ffffffff8046d3de>] __rt_spin_lock+0x34/0x7d
>  [<ffffffff8046d435>] rt_spin_lock+0xe/0x10
>  [<ffffffff802d3cfc>] mnt_want_write+0x3b/0xbc
>  [<ffffffff802cea88>] touch_atime+0x1c/0x101
>  [<ffffffff802c426c>] __link_path_walk+0x484/0xf24
>  [<ffffffff802c4d72>] path_walk+0x66/0xc9
>  [<ffffffff802c51bf>] do_path_lookup+0x209/0x264
>  [<ffffffff802c5509>] __path_lookup_intent_open+0x61/0xa4
>  [<ffffffff802c555d>] path_lookup_open+0x11/0x13
>  [<ffffffff802c61f1>] do_filp_open+0xb6/0x8f5
>  [<ffffffff8046d3de>] ? __rt_spin_lock+0x34/0x7d
>  [<ffffffff802b897d>] ? get_unused_fd_flags+0x119/0x12a
>  [<ffffffff802b89e4>] do_sys_open+0x56/0xd6
>  [<ffffffff8020c374>] ? system_call_after_swapgs+0xc4/0x168
>  [<ffffffff802b8a97>] sys_open+0x20/0x22
>  [<ffffffff8020c3ab>] system_call_after_swapgs+0xfb/0x168
>
> ---------------------------
> | preempt count: 00000001 ]
> | 1-level deep critical section nesting:
> ----------------------------------------
> .. [<ffffffff802d3cda>] .... mnt_want_write+0x19/0xbc
> .....[<ffffffff802cea88>] ..   ( <= touch_atime+0x1c/0x101)
>

Another patch that should be included in -rt3 was discussed here.
http://marc.info/?l=linux-rt-users&m=121751295105462&w=2

After some attempts at fixing this myself, Peter Zijlstra offered the
above solution (in the link) which I've been running with ever since,
no changes required, and it solved the problem.
I'm attaching the patch again, I think it would be optimal to get
Peter's Signed-off-by: on it as he is the author of the patch.
No changes or refreshing were required against 2.6.26.3-rt2

View attachment "sock_prot_inuse_add-fix.patch" of type "text/x-patch" (1068 bytes)