[2.6.18-rc2-gabb5a5cc BUG] Lukewarm IQ detected in hotplug locking

[2.6.18-rc2-gabb5a5cc BUG] Lukewarm IQ detected in hotplug locking

[Michal Piotrowski]

Hi,

This looks like an abb5a5cc6bba1516403146c5b79036fe843beb70 commit
(I'm not sure, I'll check this "tomorrow").

Jul 24 20:46:50 ltg01-fedora kernel: Lukewarm IQ detected in hotplug locking
Jul 24 20:46:50 ltg01-fedora kernel: BUG: warning at
/usr/src/linux-git/kernel/cpu.c:38/lock_cpu_hotplug()
Jul 24 20:46:50 ltg01-fedora kernel:  [<c0132891>] lock_cpu_hotplug+0x40/0x63
Jul 24 20:46:50 ltg01-fedora kernel:  [<c026a364>]
__cpufreq_driver_target+0xf/0x48
Jul 24 20:46:50 ltg01-fedora kernel:  [<c026affb>]
cpufreq_governor_performance+0x17/0x1c
Jul 24 20:46:50 ltg01-fedora kernel:  [<c026992e>] __cpufreq_governor+0x63/0x114
Jul 24 20:46:50 ltg01-fedora kernel:  [<c0269abe>]
__cpufreq_set_policy+0xdf/0xe6
Jul 24 20:46:50 ltg01-fedora kernel:  [<c026a58a>]
store_scaling_governor+0x11d/0x148
Jul 24 20:46:50 ltg01-fedora kernel:  [<c0269e27>] handle_update+0x0/0x5
Jul 24 20:46:50 ltg01-fedora kernel:  [<c026a46d>]
store_scaling_governor+0x0/0x148
Jul 24 20:46:50 ltg01-fedora kernel:  [<c026a0c0>] store+0x2e/0x3e
Jul 24 20:46:50 ltg01-fedora kernel:  [<c018c801>] sysfs_write_file+0x8c/0xb4
Jul 24 20:46:50 ltg01-fedora kernel:  [<c018c775>] sysfs_write_file+0x0/0xb4
Jul 24 20:46:50 ltg01-fedora kernel:  [<c015be27>] vfs_write+0xa1/0x143
Jul 24 20:46:50 ltg01-fedora kernel:  [<c015c417>] sys_write+0x3c/0x63
Jul 24 20:46:50 ltg01-fedora kernel:  [<c0102d51>] sysenter_past_esp+0x56/0x79

Here is a config file
http://www.stardust.webpages.pl/files/2.6-git/18-rc2/git-config

Here is dmesg http://www.stardust.webpages.pl/files/2.6-git/18-rc2/git-dmesg

Regards,
Michal

-- 
Michal K. K. Piotrowski
LTG - Linux Testers Group
(http://www.stardust.webpages.pl/ltg/wiki/)

Re: [2.6.18-rc2-gabb5a5cc BUG] Lukewarm IQ detected in hotplug locking

[Paul Jackson]

Michal - you addressed this to me.  This isn't my area.
Hopefully someone else can handle this.  Good luck.

-- 
                  I won't rest till it's the best ...
                  Programmer, Linux Scalability
                  Paul Jackson <pj@sgi.com> 1.925.600.0401

Re: [2.6.18-rc2-gabb5a5cc BUG] Lukewarm IQ detected in hotplug locking

[Michal Piotrowski]

On 26/07/06, Paul Jackson <pj@sgi.com> wrote:
> Michal - you addressed this to me.  This isn't my area.

I was wrong, sorry.

> Hopefully someone else can handle this.  Good luck.

Here is the bad commit

aa95387774039096c11803c04011f1aa42d85758 is first bad commit
commit aa95387774039096c11803c04011f1aa42d85758
Author: Linus Torvalds <torvalds@macmini.osdl.org>
Date:   Sun Jul 23 12:12:16 2006 -0700

    cpu hotplug: simplify and hopefully fix locking

    The CPU hotplug locking was quite messy, with a recursive lock to
    handle the fact that both the actual up/down sequence wanted to
    protect itself from being re-entered, but the callbacks that it
    called also tended to want to protect themselves from CPU events.

    This splits the lock into two (one to serialize the whole hotplug
    sequence, the other to protect against the CPU present bitmaps
    changing). The latter still allows recursive usage because some
    subsystems (ondemand policy for cpufreq at least) had already gotten
    too used to the lax locking, but the locking mistakes are hopefully
    now less fundamental, and we now warn about recursive lock usage
    when we see it, in the hope that it can be fixed.

    Signed-off-by: Linus Torvalds <torvalds@osdl.org>

:040000 040000 9189d56fe28f6823287e9d1e79976e68074da5db
266b4ea87d2ac441bc02ad2c
4ba2c4f332c7c0ce M      include
:040000 040000 3dfe69afef86aef8e6472d6d543ba965833e201b
bfb64b2824c1e23f0629e976
2526fd11b789d51e M      kernel

>
> --
>                   I won't rest till it's the best ...
>                   Programmer, Linux Scalability
>                   Paul Jackson <pj@sgi.com> 1.925.600.0401
>

Regards,
Michal

-- 
Michal K. K. Piotrowski
LTG - Linux Testers Group
(http://www.stardust.webpages.pl/ltg/wiki/)

Re: [2.6.18-rc2-gabb5a5cc BUG] Lukewarm IQ detected in hotplug locking

[Michal Piotrowski]

On 26/07/06, Michal Piotrowski <michal.k.k.piotrowski@gmail.com> wrote:
> Here is the bad commit
>
> aa95387774039096c11803c04011f1aa42d85758 is first bad commit
> commit aa95387774039096c11803c04011f1aa42d85758
> Author: Linus Torvalds <torvalds@macmini.osdl.org>
> Date:   Sun Jul 23 12:12:16 2006 -0700
>
>     cpu hotplug: simplify and hopefully fix locking
>
>     The CPU hotplug locking was quite messy, with a recursive lock to
>     handle the fact that both the actual up/down sequence wanted to
>     protect itself from being re-entered, but the callbacks that it
>     called also tended to want to protect themselves from CPU events.
>
>     This splits the lock into two (one to serialize the whole hotplug
>     sequence, the other to protect against the CPU present bitmaps
>     changing). The latter still allows recursive usage because some
>     subsystems (ondemand policy for cpufreq at least) had already gotten
>     too used to the lax locking, but the locking mistakes are hopefully
>     now less fundamental, and we now warn about recursive lock usage
>     when we see it, in the hope that it can be fixed.
>
>     Signed-off-by: Linus Torvalds <torvalds@osdl.org>
>
> :040000 040000 9189d56fe28f6823287e9d1e79976e68074da5db
> 266b4ea87d2ac441bc02ad2c
> 4ba2c4f332c7c0ce M      include
> :040000 040000 3dfe69afef86aef8e6472d6d543ba965833e201b
> bfb64b2824c1e23f0629e976
> 2526fd11b789d51e M      kernel

Sorry for the noise.

The bug is fixed in latest git tree.

Regards,
Michal

-- 
Michal K. K. Piotrowski
LTG - Linux Testers Group
(http://www.stardust.webpages.pl/ltg/wiki/)

Re: [2.6.18-rc2-gabb5a5cc BUG] Lukewarm IQ detected in hotplug locking

[Arjan van de Ven]

On Wed, 2006-07-26 at 17:01 +0200, Michal Piotrowski wrote:
> Sorry for the noise.
> 
> The bug is fixed in latest git tree.


Hi,

no need to be sorry; it is a very valid bug, it's just something that
took some time to get fixed (and still isn't entirely done, my testbox
is busy rebooting to a next patch to fix another case).

I'm glad the patch that Linus merged about an hour or two ago fixes this
for you. Thanks for testing that!

Greetings,
   Arjan van de Ven


-- 
if you want to mail me at work (you don't), use arjan (at) linux.intel.com