Re: [PATCH v5 7/7] sched/fair: Fair server interface

From: Joel Fernandes <joel@joelfernandes.org>
To: Daniel Bristot de Oliveira <bristot@redhat.com>,
	Daniel Bristot de Oliveira <bristot@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
	Valentin Schneider <vschneid@redhat.com>,
	linux-kernel@vger.kernel.org,
	Luca Abeni <luca.abeni@santannapisa.it>,
	Tommaso Cucinotta <tommaso.cucinotta@santannapisa.it>,
	Thomas Gleixner <tglx@linutronix.de>,
	Vineeth Pillai <vineeth@bitbyteword.org>,
	Shuah Khan <skhan@linuxfoundation.org>,
	Phil Auld <pauld@redhat.com>,
	suleiman@google.com
Subject: Re: [PATCH v5 7/7] sched/fair: Fair server interface
Date: Tue, 23 Jan 2024 10:44:27 -0500	[thread overview]
Message-ID: <0454a852-5e61-4181-b8cd-518e1cb45b58@joelfernandes.org> (raw)
In-Reply-To: <3f002616-0975-49b8-a2bf-04abd0446b95@redhat.com>

On 1/22/2024 9:14 AM, Daniel Bristot de Oliveira wrote:
> Interesting, does it keep any task hung? I am having a case where I see
> a hung task, but I do not get the splat because the system freezes (printk
> with rq_lock I guess)...

I missed replying to this part of your email. We see it as a syzkaller report
with splats, so it is not clear if a task was hung at the time of a splat.
syzkaller runs in its own separate VM instance.

The fun part is though, I found a way to do ftrace dump on it without having to
pass any boot parameters (that's another issue that we can't pass it boot
parameters). So we have that tool in our debug arsenal for these issues, thankfully.

> It might be the same problem.

True, possibly.

thanks,

 - Joel