On Tue, 2006-07-25 at 20:54 +0200, Ingo Molnar wrote:
> * Linus Torvalds <[email protected]> wrote:
>
> > The current -git tree will complain about some of the more obvious
> > problems. If you see a "Lukewarm IQ" message, it's a sign of somebody
> > re-taking a cpu lock that is already held.
>
> testing on my latest-rawhide laptop (kernel-2.6.17-1.2445.fc6 and later
> rpms have this change) seems to have pushed the problem over to another
> lock:
>
> S06cpuspeed/1580 is trying to acquire lock:
> (&policy->lock){--..}, at: [<c06075f9>] mutex_lock+0x21/0x24
>
> but task is already holding lock:
> (cpu_bitmask_lock){--..}, at: [<c06075f9>] mutex_lock+0x21/0x24
>
> which lock already depends on the new lock.
so cpufreq_set_policy() takes policy->lock, and then calls into the
userspace governer code
(__cpufreq_set_policy->cpufreq_governor->cpufreq_governor_userspace)
which calls __cpufreq_driver_target... which does lock_cpu_hotplug().
now on the other side:
store_scaling_governor() has the following code:
lock_cpu_hotplug();
/* Do not use cpufreq_set_policy here or the user_policy.max
will be wrongly overridden */
mutex_lock(&policy->lock);
so that's the entirely opposite lock order, and a classic AB-BA
deadlock.
Greetings,
Arjan -- who's just cleaned Linus' wall to prepare it for more head
banging
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
