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authorvenkatesh.pallipadi@intel.com <venkatesh.pallipadi@intel.com>2009-07-02 17:08:30 -0700
committerDave Jones <davej@redhat.com>2009-07-06 21:38:27 -0400
commit7d26e2d5e2da37e92c6c7644b26b294dedd8c982 (patch)
tree44d1637ac603fad42cbbf28ba7a89c9e194c4d0f /drivers/cpufreq/cpufreq_conservative.c
parentfaf80d62e44dc627efb741f48db50c1858d1667c (diff)
[CPUFREQ] Eliminate the recent lockdep warnings in cpufreq
Commit b14893a62c73af0eca414cfed505b8c09efc613c although it was very much needed to properly cleanup ondemand timer, opened-up a can of worms related to locking dependencies in cpufreq. Patch here defines the need for dbs_mutex and cleans up its usage in ondemand governor. This also resolves the lockdep warnings reported here http://lkml.indiana.edu/hypermail/linux/kernel/0906.1/01925.html http://lkml.indiana.edu/hypermail/linux/kernel/0907.0/00820.html and few others.. Signed-off-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com> Signed-off-by: Dave Jones <davej@redhat.com>
Diffstat (limited to 'drivers/cpufreq/cpufreq_conservative.c')
-rw-r--r--drivers/cpufreq/cpufreq_conservative.c27
1 files changed, 11 insertions, 16 deletions
diff --git a/drivers/cpufreq/cpufreq_conservative.c b/drivers/cpufreq/cpufreq_conservative.c
index 7fc58af748b..58889f26029 100644
--- a/drivers/cpufreq/cpufreq_conservative.c
+++ b/drivers/cpufreq/cpufreq_conservative.c
@@ -70,15 +70,10 @@ static DEFINE_PER_CPU(struct cpu_dbs_info_s, cpu_dbs_info);
static unsigned int dbs_enable; /* number of CPUs using this policy */
/*
- * DEADLOCK ALERT! There is a ordering requirement between cpu_hotplug
- * lock and dbs_mutex. cpu_hotplug lock should always be held before
- * dbs_mutex. If any function that can potentially take cpu_hotplug lock
- * (like __cpufreq_driver_target()) is being called with dbs_mutex taken, then
- * cpu_hotplug lock should be taken before that. Note that cpu_hotplug lock
- * is recursive for the same process. -Venki
- * DEADLOCK ALERT! (2) : do_dbs_timer() must not take the dbs_mutex, because it
- * would deadlock with cancel_delayed_work_sync(), which is needed for proper
- * raceless workqueue teardown.
+ * dbs_mutex protects data in dbs_tuners_ins from concurrent changes on
+ * different CPUs. It protects dbs_enable in governor start/stop. It also
+ * serializes governor limit_change with do_dbs_timer. We do not want
+ * do_dbs_timer to run when user is changing the governor or limits.
*/
static DEFINE_MUTEX(dbs_mutex);
@@ -488,18 +483,17 @@ static void do_dbs_timer(struct work_struct *work)
delay -= jiffies % delay;
- if (lock_policy_rwsem_write(cpu) < 0)
- return;
+ mutex_lock(&dbs_mutex);
if (!dbs_info->enable) {
- unlock_policy_rwsem_write(cpu);
+ mutex_unlock(&dbs_mutex);
return;
}
dbs_check_cpu(dbs_info);
queue_delayed_work_on(cpu, kconservative_wq, &dbs_info->work, delay);
- unlock_policy_rwsem_write(cpu);
+ mutex_unlock(&dbs_mutex);
}
static inline void dbs_timer_init(struct cpu_dbs_info_s *dbs_info)
@@ -590,15 +584,16 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
&dbs_cpufreq_notifier_block,
CPUFREQ_TRANSITION_NOTIFIER);
}
- dbs_timer_init(this_dbs_info);
-
mutex_unlock(&dbs_mutex);
+ dbs_timer_init(this_dbs_info);
+
break;
case CPUFREQ_GOV_STOP:
- mutex_lock(&dbs_mutex);
dbs_timer_exit(this_dbs_info);
+
+ mutex_lock(&dbs_mutex);
sysfs_remove_group(&policy->kobj, &dbs_attr_group);
dbs_enable--;