[cpufreq] ondemand: make shutdown sequence more robust

Shutting down the ondemand policy was fraught with potential
problems, causing issues for SMP suspend (which wants to hot-
unplug) all but the last CPU.

This should fix at least the worst problems (divide-by-zero
and infinite wait for the workqueue to shut down).

Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 10 insertions, 6 deletions

diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c
index 87299924e735..178f0c547eb7 100644
--- a/drivers/cpufreq/cpufreq_ondemand.c
+++ b/drivers/cpufreq/cpufreq_ondemand.c
@@ -239,6 +239,8 @@ static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info)
         total_ticks = (unsigned int) cputime64_sub(cur_jiffies,
                         this_dbs_info->prev_cpu_wall);
         this_dbs_info->prev_cpu_wall = cur_jiffies;
+        if (!total_ticks)
+                return;
         /*
          * Every sampling_rate, we check, if current idle time is less
          * than 20% (default), then we try to increase frequency
@@ -304,6 +306,9 @@ static void do_dbs_timer(void *data)
         unsigned int cpu = smp_processor_id();
         struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, cpu);
 
+        if (!dbs_info->enable)
+                return;
+
         dbs_check_cpu(dbs_info);
         queue_delayed_work_on(cpu, kondemand_wq, &dbs_info->work,
                         usecs_to_jiffies(dbs_tuners_ins.sampling_rate));
@@ -319,11 +324,11 @@ static inline void dbs_timer_init(unsigned int cpu)
         return;
 }
 
-static inline void dbs_timer_exit(unsigned int cpu)
+static inline void dbs_timer_exit(struct cpu_dbs_info_s *dbs_info)
 {
-        struct cpu_dbs_info_s *dbs_info = &per_cpu(cpu_dbs_info, cpu);
-
-        cancel_rearming_delayed_workqueue(kondemand_wq, &dbs_info->work);
+        dbs_info->enable = 0;
+        cancel_delayed_work(&dbs_info->work);
+        flush_workqueue(kondemand_wq);
 }
 
 static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
@@ -396,8 +401,7 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
 
         case CPUFREQ_GOV_STOP:
                 mutex_lock(&dbs_mutex);
-                dbs_timer_exit(policy->cpu);
-                this_dbs_info->enable = 0;
+                dbs_timer_exit(this_dbs_info);
                 sysfs_remove_group(&policy->kobj, &dbs_attr_group);
                 dbs_enable--;
                 if (dbs_enable == 0)