linux-kernel - Re: [GIT PULL] workqueue fixes for v4.5-rc3

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Message-ID: <CA+55aFzOPtup51mG1Evh6o9-0ypgpMwgPWVHqvM1-LdbHXBwwQ@mail.gmail.com>
Date:	Thu, 11 Feb 2016 10:56:46 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Tejun Heo <tj@...nel.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL] workqueue fixes for v4.5-rc3

On Thu, Feb 11, 2016 at 10:49 AM, Thomas Gleixner <tglx@...utronix.de> wrote:
>
> while playing around with it and wondering where to put the command line
> option, I wondered whether it makes sense to tie this to debugobjects.
>
> If stuff goes bad, then state corruptions of the involved objects (timers,
> work ..) are likely to happen, so having debugobjects enabled along with that
> force RR scheme makes a lot of sense.
>
> Thoughts?

I'm not violently opposed, but at the same time I personally
absolutely detest the debug options that are so expensive that they
are unusable in production environments. That limits the scope of
testing a lot.

debugobjects and PAGEALLOC_DEBUG are both good things, but they really
are so expensive as to be completely unusable in many situations. I
would never enable them personally unless I was actively trying to
chase something down, or for some very occasional "let's just do a
sanity check". A system admin that enabled those things on every
machine he runs would be insane (again, unless he is already in big
trouble and is actively trying to chase something down).

There's a *lot* to be said for cheap debug options that you might want
to enable "just in case". debugobjects is not that.

So I'd much prefer a standalone option. Then, *if* that shows
problems, and *if* those problems end up being hard to chase down, at
that point we might ask the people who see issues to "maybe enable
debugobjects that might give us more information".

Most oopses are not subtle.

                 Linus