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[PATCH] clean up lock_cpu_hotplug() in cpufreq

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There are some callers in cpufreq hotplug notify path that the lowest
function calls lock_cpu_hotplug().  The lock is already held during
cpu_up() and cpu_down() calls when the notify calls are broadcast to
registered clients.

Ideally if possible, we could disable_preempt() at the highest caller and
make sure we dont sleep in the path down in cpufreq->driver_target() calls
but the calls are so intertwined and cumbersome to cleanup.

Hence we consistently use lock_cpu_hotplug() and unlock_cpu_hotplug() in
all places.

 - Removed export of cpucontrol semaphore and made it static.
 - removed explicit uses of up/down with lock_cpu_hotplug()
   so we can keep track of the the callers in same thread context and
   just keep refcounts without calling a down() that causes a deadlock.
 - Removed current_in_hotplug() uses
 - Removed PF_HOTPLUG_CPU in sched.h introduced for the current_in_hotplug()
   temporary workaround.

Tested with insmod of cpufreq_stat.ko, and logical online/offline
to make sure we dont have any hang situations.

Signed-off-by: Ashok Raj <[email protected]>
Cc: Zwane Mwaikambo <[email protected]>
Cc: Shaohua Li <[email protected]>
Cc: "Siddha, Suresh B" <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>
This commit is contained in:
Ashok Raj 2005-11-28 13:43:46 -08:00 • committed by Linus Torvalds
commit a9d9baa1e8
4 changed files with 54 additions and 49 deletions
Download patch file Download diff file Expand all files Collapse all files

12
drivers/cpufreq/cpufreq.c
View file

@ -1113,21 +1113,13 @@ int __cpufreq_driver_target(struct cpufreq_policy *policy,
{
int retval = -EINVAL;
/*
* If we are already in context of hotplug thread, we dont need to
* acquire the hotplug lock. Otherwise acquire cpucontrol to prevent
* hotplug from removing this cpu that we are working on.
*/
if (!current_in_cpu_hotplug())
lock_cpu_hotplug();
lock_cpu_hotplug();
dprintk("target for CPU %u: %u kHz, relation %u\n", policy->cpu,
target_freq, relation);
if (cpu_online(policy->cpu) && cpufreq_driver->target)
retval = cpufreq_driver->target(policy, target_freq, relation);
if (!current_in_cpu_hotplug())
unlock_cpu_hotplug();
unlock_cpu_hotplug();
return retval;
}