[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-Id: <201404240832.s3O8WHd0011014@toshiba.co.jp>
Date: Thu, 24 Apr 2014 17:31:55 +0900
From: Daniel Sangorrin <daniel.sangorrin@...hiba.co.jp>
To: Viresh Kumar <viresh.kumar@...aro.org>,
Daniel Sangorrin <daniel.sangorrin@...hiba.co.jp>
Cc: Thomas Gleixner <tglx@...utronix.de>,
Frédéric Weisbecker
<fweisbec@...il.com>, Peter Zijlstra <peterz@...radead.org>,
Ingo Molnar <mingo@...nel.org>, Tejun Heo <tj@...nel.org>,
Li Zefan <lizefan@...wei.com>,
Lists linaro-kernel <linaro-kernel@...ts.linaro.org>,
Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
Cgroups <cgroups@...r.kernel.org>
Subject: Re: [RFC 0/4] Migrate timers away from cpuset on setting cpuset.quiesce
On 2014/04/24 16:43, Viresh Kumar wrote:
> On 24 April 2014 12:55, Daniel Sangorrin <daniel.sangorrin@...hiba.co.jp> wrote:
>> I tried your set of patches for isolating particular CPU cores from unpinned
>> timers. On x86_64 they were working fine, however I found out that on ARM
>> they would fail under the following test:
>
> I am happy that these drew attention from somebody Atleast :)
Thanks to you for your hard work.
>> # mount -t cpuset none /cpuset
>> # cd /cpuset
>> # mkdir rt
>> # cd rt
>> # echo 1 > cpus
>> # echo 1 > cpu_exclusive
>> # cd
>> # taskset 0x2 ./setquiesce.sh <--- contains "echo 1 > /cpuset/rt/quiesce"
>> [ 75.622375] ------------[ cut here ]------------
>> [ 75.627258] WARNING: CPU: 0 PID: 0 at kernel/locking/lockdep.c:2595 __migrate_hrtimers+0x17c/0x1bc()
>> [ 75.636840] DEBUG_LOCKS_WARN_ON(current->hardirq_context)
>> [ 75.636840] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 3.14.0-rc1-37710-g23c8f02 #1
>> [ 75.649627] [<c0014d18>] (unwind_backtrace) from [<c00119e8>] (show_stack+0x10/0x14)
>> [ 75.649627] [<c00119e8>] (show_stack) from [<c065b61c>] (dump_stack+0x78/0x94)
>> [ 75.662689] [<c065b61c>] (dump_stack) from [<c003e9a4>] (warn_slowpath_common+0x60/0x84)
>> [ 75.670410] [<c003e9a4>] (warn_slowpath_common) from [<c003ea24>] (warn_slowpath_fmt+0x30/0x40)
>> [ 75.677673] [<c003ea24>] (warn_slowpath_fmt) from [<c005d7b0>] (__migrate_hrtimers+0x17c/0x1bc)
>> [ 75.677673] [<c005d7b0>] (__migrate_hrtimers) from [<c009e004>] (generic_smp_call_function_single_interrupt+0x8c/0x104)
>> [ 75.699645] [<c009e004>] (generic_smp_call_function_single_interrupt) from [<c00134d0>] (handle_IPI+0xa4/0x16c)
>> [ 75.706970] [<c00134d0>] (handle_IPI) from [<c0008614>] (gic_handle_irq+0x54/0x5c)
>> [ 75.715087] [<c0008614>] (gic_handle_irq) from [<c0012624>] (__irq_svc+0x44/0x5c)
>> [ 75.725311] Exception stack(0xc08a3f58 to 0xc08a3fa0)
>
> I couldn't understand why we went via a interrupt here ? Probably CPU1
> was idle and was woken up with a IPI and then this happened. But in
> that case too,
> shouldn't the script run from process context instead ?
In kernel/cpuset.c:quiesce_cpuset() you are using the function
'smp_call_function_any' which asks CPU cores in 'cpumask' to
execute the functions 'hrtimer_quiesce_cpu' and 'timer_quiesce_cpu'.
In the case above, 'cpumask' corresponds to core 0. Since I'm forcing
the call to be executed from core 1 (by using taskset),
an inter-processor interrupt is sent to core 0 for those functions
to be executed.
>> I also backported your patches to Linux 3.10.y and found the same problem
>> both in ARM and x86_64.
>
> There are very few changes in between 3.10 and latest for timers/hrtimers
> and so things are expected to be the same.
>
>> However, I think I figured out the reason for those
>> errors. Please, could you check the patch below (it applies on the top of
>> your tree, branch isolate-cpusets) and let me know what you think?
>
> Okay, just to let you know, I have also found some issues and they are
> now pushed in my tree.. Also it is rebased over 3.15-rc2 now.
Ok, thank you! I see that you have already fixed the problem. I tested
your tree on ARM and now it seems to work correctly.
>
>> -------------------------PATCH STARTS HERE---------------------------------
>> cpuset: quiesce: change irq disable/enable by irq save/restore
>>
>> The function __migrate_timers can be called under interrupt context
>> or thread context depending on the core where the system call was
>> executed. In case it executes under interrupt context, it
>
> How exactly?
See my reply above.
>> seems a bad idea to leave interrupts enabled after migrating the
>> timers. In fact, this caused kernel errors on the ARM architecture and
>> on the x86_64 architecture with the 3.10 kernel (backported version
>> of the cpuset-quiesce patch).
>
> I can't keep it as a separate patch and so would be required to merge
> it into my original patch..
>
> Thanks for your inputs :)
> --
> To unsubscribe from this list: send the line "unsubscribe cgroups" in
> the body of a message to majordomo@...r.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
>
>
Thanks,
Daniel
--
Toshiba Corporate Software Engineering Center
Daniel SANGORRIN
E-mail: daniel.sangorrin@...hiba.co.jp
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists