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

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Message-ID: <6bffcb0e0607260801s73cdee9avd207984712011c80@mail.gmail.com>
Date:	Wed, 26 Jul 2006 17:01:26 +0200
From:	"Michal Piotrowski" <michal.k.k.piotrowski@...il.com>
To:	torvalds@...l.org
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [2.6.18-rc2-gabb5a5cc BUG] Lukewarm IQ detected in hotplug locking

On 26/07/06, Michal Piotrowski <michal.k.k.piotrowski@...il.com> wrote:
> Here is the bad commit
>
> aa95387774039096c11803c04011f1aa42d85758 is first bad commit
> commit aa95387774039096c11803c04011f1aa42d85758
> Author: Linus Torvalds <torvalds@...mini.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@...l.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/)
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