linux-kernel - Re: Linux 3.19-rc5

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Message-ID: <CA+55aFwW139HZ6aNi_2Jf36kx53znZMKS1QO_4JVXJJYsSG6=A@mail.gmail.com>
Date:	Sat, 31 Jan 2015 10:32:23 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Hurley <peter@...leysoftware.com>,
	Davidlohr Bueso <dave@...olabs.net>,
	Peter Zijlstra <peterz@...radead.org>,
	Bruno Prémont <bonbons@...ux-vserver.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ilya Dryomov <ilya.dryomov@...tank.com>,
	Mike Galbraith <umgwanakikbuti@...il.com>
Subject: Re: Linux 3.19-rc5

On Fri, Jan 30, 2015 at 7:47 AM, Oleg Nesterov <oleg@...hat.com> wrote:
>
> Perhaps sched_annotate_sleep() shouldn't depend on CONFIG_DEBUG_ATOMIC_SLEEP
> too...

Ugh. That thing is horrible. The naming doesn't make it obvious at all
that it's actually making sure that we have state set to TASK_RUNNING,
and I could easily imagine that it would cause similar "busy-loops
while scheduling" issues if anybody ever uses it in the wrong context.

So I really think that whole thing is a sign of "the debug
infrastructure is buggy, and people are introducing fragile things to
just shut up the false positives".

I don't know how to fix it. I really get the feeling that the whole
new "nested sleep" detection code was a mistake to begin with, since
it wasn't even a real bug, and it has now created more bugs than it
ever detected afaik.

                              Linus
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