linux-kernel - Re: [Bug #12872] pwc mmap always fails with EAGAIN

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Date:	Sun, 22 Mar 2009 20:58:12 +0100
From:	Markus <M4rkusXXL@....de>
To:	linux-kernel@...r.kernel.org
Cc:	Ingo Molnar <mingo@...e.hu>, Alan Cox <alan@...rguk.ukuu.org.uk>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Kernel Testers List <kernel-testers@...r.kernel.org>
Subject: Re: [Bug #12872] pwc mmap always fails with EAGAIN

> > > Still valid for 2.6.29-rc8-git5.
> > 
> > And not really likely to change until someone with a pwc camera adds 
lots
> > of printks to the code to work out why this happens.
> 
> Or does a bisection to figure out the bad commit, because the report 
> says that 2.6.28 worked.
> 
> The 'howto bisect' portion of:
> 
>   http://www.kernel.org/doc/local/git-quick.html


Well I did a bisect:
be03d9e8022030c16abf534e33e185bfc3d40eef is first bad commit
commit be03d9e8022030c16abf534e33e185bfc3d40eef
Author: Suresh Siddha <suresh.b.siddha@...el.com>
Date:   Wed Feb 11 11:20:23 2009 -0800

    x86, pat: fix warn_on_once() while mapping 0-1MB range with /dev/mem

    Jeff Mahoney reported:

    > With Suse's hwinfo tool, on -tip:
    > WARNING: at arch/x86/mm/pat.c:637 reserve_pfn_range+0x5b/0x26d()

    reserve_pfn_range() is not tracking the memory range below 1MB
    as non-RAM and as such is inconsistent with similar checks in
    reserve_memtype() and free_memtype()

    Rename the pagerange_is_ram() to pat_pagerange_is_ram() and add the
    "track legacy 1MB region as non RAM" condition.

    And also, fix reserve_pfn_range() to return -EINVAL, when the pfn
    range is RAM. This is to be consistent with this API design.

    Reported-and-tested-by: Jeff Mahoney <jeffm@...e.com>
    Signed-off-by: Suresh Siddha <suresh.b.siddha@...el.com>
    Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@...el.com>
    Signed-off-by: Ingo Molnar <mingo@...e.hu>

:040000 040000 feb3bf21d762e885284cb1bedb5d2c6c0d16811b 
b4c2143775386ce15dd49b6749c1f7913d8beb00 M      arch

So I ran "git bisect reset ; git revert 
be03d9e8022030c16abf534e33e185bfc3d40eef" and rebuild. That worked!

I dont know if this is valid to do, but its working fine.
Its an amd64 system with CONFIG_X86_PAT=y.

Need some feedback ;)

Markus
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