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From: Vladimir Oltean <olteanv@gmail.com>
To: Kurt Kanzenbach <kurt.kanzenbach@linutronix.de>
Cc: Alison Wang <alison.wang@nxp.com>,
	catalin.marinas@arm.com, will@kernel.org, paulmck@kernel.org,
	mw@semihalf.com, leoyang.li@nxp.com, vladimir.oltean@nxp.com,
	linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Anna-Maria Gleixner <anna-maria@linutronix.de>
Subject: Re: [RFC PATCH] arm64: defconfig: Disable fine-grained task level IRQ time accounting
Date: Thu, 30 Jul 2020 11:22:28 +0300	[thread overview]
Message-ID: <20200730082228.r24zgdeiofvwxijm@skbuf> (raw)
In-Reply-To: <87mu3ho48v.fsf@kurt>

On Thu, Jul 30, 2020 at 09:23:44AM +0200, Kurt Kanzenbach wrote:
> Hi Vladimir,
> 
> On Wed Jul 29 2020, Vladimir Oltean wrote:
> > For more context, here is my original report of the issue:
> > https://lkml.org/lkml/2020/6/4/1062
> >
> > Just like you, I could not reproduce the RCU stalls and system hang on a
> > 5.6-rt kernel, just on mainline and derivatives, using the plain
> > defconfig.
> >
> > The issue is not specific to Layerscape or i.MX8, but rather I was able
> > to see the same behavior on Marvell Armada 37xx as well as Qualcomm
> > MSM8976.
> >
> > So, while of course I agree that disabling IRQ time accounting for arm64
> > isn't a real solution, it isn't by far an exaggerated proposal either.
> > Nonetheless, the patch is just a RFC and should be treated as such. We
> > are at a loss when it comes to debugging this any further and we would
> > appreciate some pointers.
> 
> Yeah, sure. I'll try to reproduce this issue first. So it triggers with:
> 
>  * arm64
>  * mainline, not -rt kernel
>  * opened serial console
>  * irq accounting enabled
> 
> Anything else?
> 
> Thanks,
> Kurt

Thanks for giving a helping hand, Kurt. The defconfig should be enough.
In the interest of full disclosure, the only arm64 device on which we
didn't reproduce this was the 16-core LX2160A. But we did reproduce on
that with maxcpus=1 though. And also on msm8976 with all 8 cores booted.
Just mentioning this in case you're testing on a 16-core system, you
might want to reduce the number a bit.

Thanks,
-Vladimir

WARNING: multiple messages have this Message-ID (diff)
From: Vladimir Oltean <olteanv@gmail.com>
To: Kurt Kanzenbach <kurt.kanzenbach@linutronix.de>
Cc: paulmck@kernel.org,
	Anna-Maria Gleixner <anna-maria@linutronix.de>,
	catalin.marinas@arm.com, Alison Wang <alison.wang@nxp.com>,
	linux-kernel@vger.kernel.org, leoyang.li@nxp.com,
	vladimir.oltean@nxp.com, Thomas Gleixner <tglx@linutronix.de>,
	mw@semihalf.com, will@kernel.org,
	linux-arm-kernel@lists.infradead.org
Subject: Re: [RFC PATCH] arm64: defconfig: Disable fine-grained task level IRQ time accounting
Date: Thu, 30 Jul 2020 11:22:28 +0300	[thread overview]
Message-ID: <20200730082228.r24zgdeiofvwxijm@skbuf> (raw)
In-Reply-To: <87mu3ho48v.fsf@kurt>

On Thu, Jul 30, 2020 at 09:23:44AM +0200, Kurt Kanzenbach wrote:
> Hi Vladimir,
> 
> On Wed Jul 29 2020, Vladimir Oltean wrote:
> > For more context, here is my original report of the issue:
> > https://lkml.org/lkml/2020/6/4/1062
> >
> > Just like you, I could not reproduce the RCU stalls and system hang on a
> > 5.6-rt kernel, just on mainline and derivatives, using the plain
> > defconfig.
> >
> > The issue is not specific to Layerscape or i.MX8, but rather I was able
> > to see the same behavior on Marvell Armada 37xx as well as Qualcomm
> > MSM8976.
> >
> > So, while of course I agree that disabling IRQ time accounting for arm64
> > isn't a real solution, it isn't by far an exaggerated proposal either.
> > Nonetheless, the patch is just a RFC and should be treated as such. We
> > are at a loss when it comes to debugging this any further and we would
> > appreciate some pointers.
> 
> Yeah, sure. I'll try to reproduce this issue first. So it triggers with:
> 
>  * arm64
>  * mainline, not -rt kernel
>  * opened serial console
>  * irq accounting enabled
> 
> Anything else?
> 
> Thanks,
> Kurt

Thanks for giving a helping hand, Kurt. The defconfig should be enough.
In the interest of full disclosure, the only arm64 device on which we
didn't reproduce this was the 16-core LX2160A. But we did reproduce on
that with maxcpus=1 though. And also on msm8976 with all 8 cores booted.
Just mentioning this in case you're testing on a 16-core system, you
might want to reduce the number a bit.

Thanks,
-Vladimir

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  reply	other threads:[~2020-07-30  8:22 UTC|newest]

Thread overview: 62+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-29  3:39 [RFC PATCH] arm64: defconfig: Disable fine-grained task level IRQ time accounting Alison Wang
2020-07-29  3:39 ` Alison Wang
2020-07-29  8:40 ` Kurt Kanzenbach
2020-07-29  8:40   ` Kurt Kanzenbach
2020-07-29  8:50   ` [EXT] " Alison Wang
2020-07-29  8:50     ` Alison Wang
2020-07-29  9:49   ` Vladimir Oltean
2020-07-29  9:49     ` Vladimir Oltean
2020-07-30  7:23     ` Kurt Kanzenbach
2020-07-30  7:23       ` Kurt Kanzenbach
2020-07-30  8:22       ` Vladimir Oltean [this message]
2020-07-30  8:22         ` Vladimir Oltean
2020-08-03  8:04         ` Kurt Kanzenbach
2020-08-03  8:04           ` Kurt Kanzenbach
2020-08-03  8:16           ` Vladimir Oltean
2020-08-03  8:16             ` Vladimir Oltean
2020-08-03  9:51             ` Robin Murphy
2020-08-03  9:51               ` Robin Murphy
2020-08-03 11:38               ` Vladimir Oltean
2020-08-03 11:38                 ` Vladimir Oltean
2020-08-03 11:48                 ` Valentin Schneider
2020-08-03 11:48                   ` Valentin Schneider
2020-08-03 13:24                   ` Marc Zyngier
2020-08-03 13:24                     ` Marc Zyngier
2020-08-03 10:02             ` Thomas Gleixner
2020-08-03 10:02               ` Thomas Gleixner
2020-08-03 10:49           ` Thomas Gleixner
2020-08-03 10:49             ` Thomas Gleixner
2020-08-03 11:41             ` Vladimir Oltean
2020-08-03 11:41               ` Vladimir Oltean
2020-08-03 15:13               ` Thomas Gleixner
2020-08-03 15:13                 ` Thomas Gleixner
2020-08-03 15:47                 ` Valentin Schneider
2020-08-03 15:47                   ` Valentin Schneider
2020-08-03 16:14                   ` Vladimir Oltean
2020-08-03 16:14                     ` Vladimir Oltean
2020-08-03 19:22                   ` Thomas Gleixner
2020-08-03 19:22                     ` Thomas Gleixner
2020-08-03 23:59                     ` Valentin Schneider
2020-08-03 23:59                       ` Valentin Schneider
2020-08-05  8:50                       ` Dietmar Eggemann
2020-08-05  8:50                         ` Dietmar Eggemann
2020-08-05 13:40                     ` peterz
2020-08-05 13:40                       ` peterz
2020-08-05 13:56                       ` Valentin Schneider
2020-08-05 13:56                         ` Valentin Schneider
2020-08-05 15:31                         ` peterz
2020-08-05 15:31                           ` peterz
2020-08-06  9:41                           ` Thomas Gleixner
2020-08-06  9:41                             ` Thomas Gleixner
2020-08-06 11:45                             ` peterz
2020-08-06 11:45                               ` peterz
2020-08-06 13:27                               ` Paul E. McKenney
2020-08-06 13:27                                 ` Paul E. McKenney
2020-08-06 19:03                                 ` Thomas Gleixner
2020-08-06 19:03                                   ` Thomas Gleixner
2020-08-06 20:39                                   ` Paul E. McKenney
2020-08-06 20:39                                     ` Paul E. McKenney
2020-08-06 18:58                               ` Thomas Gleixner
2020-08-06 18:58                                 ` Thomas Gleixner
2020-08-06  9:34                       ` Thomas Gleixner
2020-08-06  9:34                         ` Thomas Gleixner

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