linux-kernel - Re: suspend regression in 4.1-rc1

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Message-ID: <CA+55aFy2wWy-k0O-Sb2vUCLiLjeKMu7r95bf294qP5UqQHuxfw@mail.gmail.com>
Date:	Sun, 17 May 2015 21:33:56 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Michal Hocko <mhocko@...e.cz>,
	Stephane Eranian <eranian@...gle.com>
Cc:	Ulrich Obergfell <uobergfe@...hat.com>,
	Don Zickus <dzickus@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Kevin Hilman <khilman@...nel.org>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	"linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: Re: suspend regression in 4.1-rc1

On Sun, May 17, 2015 at 11:50 AM, Michal Hocko <mhocko@...e.cz> wrote:
>
> The merge commit is empty and both 80dcc31fbe55 and e4b0db72be24 work
> properly but the merge is bad. So it seems like some of the commits in
> either branch has a side effect which needs other branch in order to
> reproduce.
>
> So've tried to bisect ^80dcc31fbe55 e4b0db72be24 and merged 80dcc31fbe55
> in each step.

Good extra work! Thanks.

> This lead to:
>
> commit 195daf665a6299de98a4da3843fed2dd9de19d3a
> Author: Ulrich Obergfell <uobergfe@...hat.com>
> Date:   Tue Apr 14 15:44:13 2015 -0700
>
>     watchdog: enable the new user interface of the watchdog mechanism
>
> The patch doesn't revert because of follow up changes so I have reverted
> all three:
> 692297d8f968 ("watchdog: introduce the hardlockup_detector_disable() function")
> b2f57c3a0df9 ("watchdog: clean up some function names and arguments")
> 195daf665a62 ("watchdog: enable the new user interface of the watchdog mechanism")

Hmm. I guess we should just revert those three then. Unless somebody
can see what the subtle interaction is.

Actually, looking closer, on the *other* side of the merge, the only
commit that looks like it might be conflicting is

    b3738d293233 "watchdog: Add watchdog enable/disable all functions"

which is then used by

    b37609c30e41 "perf/x86/intel: Make the HT bug workaround
conditional on HT enabled"

Does the problem go away if you revert *those* two commits instead?

At least that would tell is what the exact bad interaction is.

Adding Stephane (author of those watchdog/perf patches) to the Cc. And
PeterZ, who signed them off (Ingo also did, but was already on the
participants list).

Anybody see it?

               Linus
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