linux-kernel - Re: [PATCH v3] fs: record task name which froze superblock

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Date:	Wed, 4 Mar 2015 18:14:35 +0300
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Mateusz Guzik <mguzik@...hat.com>
Cc:	Dave Chinner <david@...morbit.com>, Jan Kara <jack@...e.cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	swhiteho@...hat.com, cluster-devel@...hat.com
Subject: Re: [PATCH v3] fs: record task name which froze superblock

On Mon, Mar 2, 2015 at 7:38 AM, Mateusz Guzik <mguzik@...hat.com> wrote:

> As explained below, this one task name is already very useful and likely
> covers majority of real life use cases.
>
> While working in support we were getting a lot of vmcores where hung task
> detector panicked the kernel because a lot of tasks were blocked
> in UN state trying to write to frozen filesystems. I presume OP has
> similar story.

Yes, the intended "use" case is 1 freezer which hopefully covers
majority of bug reports.

> Some back on forth commuication almost always revealed one process e.g.
> freezing stuff and then blocking itself trying to access it. While we
> could see it blocked, we had no presumptive evidence to pin freezing on
> it. A matching name, while still not 100% conclusive, would be ok enough
> to push the case forward and avoid a rountrip of systemap scripts
> showing freezer process tree.
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