lkml.org 
[lkml]   [2006]   [Aug]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC][PATCH 0/4] Redesign cpu_hotplug locking.
On Sat, Aug 26, 2006 at 11:46:18PM -0700, Andrew Morton wrote:
> On Sun, 27 Aug 2006 11:41:55 +0530
>
> > The right thing to do would be to
> > do an audit and clean up the bad lock_cpu_hotplug() calls.
>
> No, that won't fix it. For example, take a look at all the *callers* of
> cpufreq_update_policy(). AFAICT they're all buggy. Fiddling with the
> existing lock_cpu_hotplug() sites won't fix that. (Possibly this
> particular problem can be fixed by checking that the relevant CPU is still
> online after the appropriate locking has been taken - dunno).
>

This is a different issue from the ones that relates to lock_cpu_hotplug().
This one seems like a cpufreq internal locking problem.

On a quick look at this, it seems to me that cpufreq_cpu_get() should
do exactly what you said - use a spinlock in each cpufreq_cpu_data[] to
protect the per-cpu flag and in cpufreq_cpu_get() check if
!data and data->online == 0. They may have to do -

static struct cpufreq_data {
spinlock_t lock;
int flag;
struct cpufreq_policy *policy;
} cpufreq_cpu_data[NR_CPUS];

Thanks
Dipankar
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

\
 
 \ /
  Last update: 2006-08-27 09:41    [from the cache]
©2003-2014 Jasper Spaans. Advertise on this site