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From: Steven Rostedt <rostedt@goodmis.org>
To: Sven Schnelle <svens@linux.ibm.com>
Cc: LKML <linux-kernel@vger.kernel.org>, lkp@lists.01.org
Subject: Re: [tracing] 06e0a548ba: WARNING:at_kernel/trace/ring_buffer.c:#ring_buffer_iter_peek
Date: Wed, 13 May 2020 12:25:24 -0400	[thread overview]
Message-ID: <20200513122524.2352c105@gandalf.local.home> (raw)
In-Reply-To: <20200513161557.GA73453@tuxmaker.boeblingen.de.ibm.com>

On Wed, 13 May 2020 18:15:57 +0200
Sven Schnelle <svens@linux.ibm.com> wrote:

> Thanks for looking into this. I've attached my /proc/config.gz to this Mail.
> The x86 system is my Laptop which is a Thinkpad X280 with 4 HT CPUs (so 8 cpus
> in total). I've tried disabling preemption, but this didn't help.
> 
> It's always this check that causes the loop:
> 
> if (iter->head >= rb_page_size(iter->head_page)) {
> 	rb_inc_iter(iter);
> 	goto again;
> }
> 
> On the first loop iter->head is some value > 0 and rb_page_size returns
> 0, afterwards it gets twice to this check with both values 0. The third
> time the warning is triggered. Maybe that information helps.

Letting it run long enough, I was able to trigger it.

I think I know what's wrong with it. I'll put in some debugging to see if
my thoughts are accurate.

Thanks for bringing this back to my attention.

-- Steve

WARNING: multiple messages have this Message-ID (diff)
From: Steven Rostedt <rostedt@goodmis.org>
To: lkp@lists.01.org
Subject: Re: [tracing] 06e0a548ba: WARNING:at_kernel/trace/ring_buffer.c:#ring_buffer_iter_peek
Date: Wed, 13 May 2020 12:25:24 -0400	[thread overview]
Message-ID: <20200513122524.2352c105@gandalf.local.home> (raw)
In-Reply-To: <20200513161557.GA73453@tuxmaker.boeblingen.de.ibm.com>

[-- Attachment #1: Type: text/plain, Size: 906 bytes --]

On Wed, 13 May 2020 18:15:57 +0200
Sven Schnelle <svens@linux.ibm.com> wrote:

> Thanks for looking into this. I've attached my /proc/config.gz to this Mail.
> The x86 system is my Laptop which is a Thinkpad X280 with 4 HT CPUs (so 8 cpus
> in total). I've tried disabling preemption, but this didn't help.
> 
> It's always this check that causes the loop:
> 
> if (iter->head >= rb_page_size(iter->head_page)) {
> 	rb_inc_iter(iter);
> 	goto again;
> }
> 
> On the first loop iter->head is some value > 0 and rb_page_size returns
> 0, afterwards it gets twice to this check with both values 0. The third
> time the warning is triggered. Maybe that information helps.

Letting it run long enough, I was able to trigger it.

I think I know what's wrong with it. I'll put in some debugging to see if
my thoughts are accurate.

Thanks for bringing this back to my attention.

-- Steve

  reply	other threads:[~2020-05-13 16:25 UTC|newest]

Thread overview: 11+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-04-29  9:05 [tracing] 06e0a548ba: WARNING:at_kernel/trace/ring_buffer.c:#ring_buffer_iter_peek kernel test robot
2020-04-29  9:05 ` kernel test robot
2020-05-13  9:19 ` Sven Schnelle
2020-05-13 13:29   ` Steven Rostedt
2020-05-13 13:29     ` Steven Rostedt
2020-05-13 16:15     ` Sven Schnelle
2020-05-13 16:25       ` Steven Rostedt [this message]
2020-05-13 16:25         ` Steven Rostedt
2020-05-13 19:30       ` Steven Rostedt
2020-05-13 19:30         ` Steven Rostedt
2020-05-14  6:09         ` Sven Schnelle

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