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Re: resume from s2ram regression (bisected to ftrace...)

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[view original message]
From: Marcin Slusarz
Subject: resume from s2ram regression (bisected to ftrace...)
Date: Sunday, August 10, 2008 - 10:08 am

Hi

Few days ago I discovered that resume from suspend to ram does not work anymore
on my 2.6.27-rc2 (actually 796aadeb1b2db9b5d463946766c5bbfd7717158c) gentoo box.
My computer just boots on resume. Today I had enough time to bisect it and found
(after 1 panic and 1 build breakage) out "the reason":

$ git bisect good
d05cdb25d80f06f77aa6bddb53cd1390d4d91a0b is first bad commit
commit d05cdb25d80f06f77aa6bddb53cd1390d4d91a0b
Author: Steven Rostedt <rostedt@goodmis.org>
Date:   Mon May 12 21:20:54 2008 +0200

    ftrace: fix dynamic ftrace selftest

    With the adding of the configuration changes in the Makefile to prevent
    tracing of functions in the ftrace code, all tracing of all the ftrace
    code has been removed. Unfortunately, one of the selftests, relied on
    a function to be traced. With the new change, the function was no longer
    traced and the test failed.

    This patch separates out the test function into its own file so that
    we can add the "-pg" flag to the compilation of that function and the
    adding of the mcount call to that function.

    Signed-off-by: Steven Rostedt <srostedt@redhat.com>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>

$ git bisect log
git-bisect start
# bad: [0967d61ea0d8e8a7826bd8949cd93dd1e829ac55] Linux 2.6.27-rc2
git-bisect bad 0967d61ea0d8e8a7826bd8949cd93dd1e829ac55
# good: [bce7f793daec3e65ec5c5705d2457b81fe7b5725] Linux 2.6.26
git-bisect good bce7f793daec3e65ec5c5705d2457b81fe7b5725
# bad: [49997d75152b3d23c53b0fa730599f2f74c92c65] Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/torvalds/linux-2.6
git-bisect bad 49997d75152b3d23c53b0fa730599f2f74c92c65
# bad: [43d2548bb2ef7e6d753f91468a746784041e522d] Merge commit '85082fd7cbe3173198aac0eb5e85ab1edcc6352c' into test-build
git-bisect bad 43d2548bb2ef7e6d753f91468a746784041e522d
# bad: [5806b81ac1c0c52665b91723fd4146a4f86e386b] Merge branch 'auto-ftrace-next' into tracing/for-linus
git-bisect bad 5806b81ac1c0c52665b91723fd4146a4f86e386b
# ...
[ message continues ]
[view original message]
From: Rafael J. Wysocki
Subject: Re: resume from s2ram regression (bisected to ftrace...)
Date: Sunday, August 10, 2008 - 10:40 am

Does it still happen if:
- CONFIG_FTRACE is unset
- CONFIG_FTRACE is set, but CONFIG_FTRACE_STARTUP_TEST is unset?

Rafael
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[view original message]
From: Marcin Slusarz
Subject: Re: resume from s2ram regression (bisected to ftrace...)
Date: Sunday, August 10, 2008 - 12:24 pm

yes

Marcin
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[view original message]
From: Rafael J. Wysocki
Subject: Re: resume from s2ram regression (bisected to ftrace...)
Date: Sunday, August 10, 2008 - 12:48 pm

Thanks for testing.

Well, ftrace is a new feature in 2.6.27, IIRC, so this is not a regression in
the strict sense.

Still, of couse, there is a bug in ftrace that needs to be fixed.  Steven?
--


[ message continues ]
[view original message]
From: Steven Rostedt
Subject: Re: resume from s2ram regression (bisected to ftrace...)
Date: Monday, August 11, 2008 - 11:27 am

Sorry for the late response.

Red Hat changed its mail servers, and my mail was in limbo for a while.

I'm not doubting that FTRACE enabled breaks suspend to ram, but I find 
it highly unlikely that the commit you posted was the culprit. 
Especially since it still breaks when STARTUP_TEST is disabled. That 
change was a STARTUP_TEST change only.  Perhaps it just moved things 
around enough to cause your issues.

But you say that if you take Linus's latest git tree, and revert only 
this change, it works??

Hmm, this is very strange.

-- Steve


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[ message continues ]
[view original message]
From: Marcin Slusarz
Subject: Re: resume from s2ram regression (bisected to ftrace...)
Date: Tuesday, August 12, 2008 - 9:37 am

I agree. Any idea how to debug it?

Marcin
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