[CPUFREQ] Rewrite lock in cpufreq to eliminate cpufreq/hotplug related issues

Yet another attempt to resolve cpufreq and hotplug locking issues.

Patchset has 3 patches:
* Rewrite the lock infrastructure of cpufreq using a per cpu rwsem.
* Minor restructuring of work callback in ondemand driver.
* Use the new cpufreq rwsem infrastructure in ondemand work.

This patch:

Convert policy->lock to rwsem and move it to per_cpu area.
This rwsem will protect against both changing/accessing policy
related parameters and CPU hot plug/unplug.

[malattia@linux.it: fix oops in kref_put()]
Cc: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
Cc: Gautham R Shenoy <ego@in.ibm.com>
Signed-off-by: Mattia Dongili <malattia@linux.it>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Dave Jones <davej@redhat.com>

1 files changed, 6 insertions, 4 deletions

diff --git a/include/linux/cpufreq.h b/include/linux/cpufreq.h
index 7f008f6bfdc3..0899e2cdcdd1 100644
--- a/include/linux/cpufreq.h
+++ b/include/linux/cpufreq.h
@@ -84,9 +84,6 @@ struct cpufreq_policy {
         unsigned int            policy; /* see above */
         struct cpufreq_governor *governor; /* see below */
 
-        struct mutex            lock;   /* CPU ->setpolicy or ->target may
-                                           only be called once a time */
-
         struct work_struct      update; /* if update_policy() needs to be
                                          * called, but you're in IRQ context */
 
@@ -172,11 +169,16 @@ extern int __cpufreq_driver_target(struct cpufreq_policy *policy,
                                    unsigned int relation);
 
 
-extern int cpufreq_driver_getavg(struct cpufreq_policy *policy);
+extern int __cpufreq_driver_getavg(struct cpufreq_policy *policy);
 
 int cpufreq_register_governor(struct cpufreq_governor *governor);
 void cpufreq_unregister_governor(struct cpufreq_governor *governor);
 
+int lock_policy_rwsem_read(int cpu);
+int lock_policy_rwsem_write(int cpu);
+void unlock_policy_rwsem_read(int cpu);
+void unlock_policy_rwsem_write(int cpu);
+
 
 /*********************************************************************
  *                      CPUFREQ DRIVER INTERFACE                     *