[PATCH -next 0/2] cpufreq: powernv: Fixes for Global pstate management

Fixes are based on patch https://patchwork.ozlabs.org/patch/612058/ which is
in Rafael's linux-next.

- Patch [1] fixes WARN_ON in powernv_target_index()
- Patch [2] Deleting any pending timer to saves an unnecessary irq call
 in powernv_target_index()


Akshay Adiga (2):
  cpufreq: powernv: Move smp_call_function_any() out of irq safe block
  cpufreq: powernv: del_timer_sync when global and local pstate are
    equal

 drivers/cpufreq/powernv-cpufreq.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

-- 
2.5.5

Deleting pending gpstates->timer for the policy when global and local pstate
are equal while executing target_index(). This saves an unnecessary
irq call.

Signed-off-by: Akshay Adiga <redacted>
---
Patch is based on Rafael's linux-next
 drivers/cpufreq/powernv-cpufreq.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index 1f0e20c..54c4536 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c

@@ -647,6 +647,8 @@ static int powernv_cpufreq_target_index(struct cpufreq_policy *policy,
 	 */
 	if (gpstate_id != freq_data.pstate_id)
 		queue_gpstate_timer(gpstates);
+	else
+		del_timer_sync(&gpstates->timer);
 
 gpstates_done:
 	freq_data.gpstate_id = gpstate_id;

-- 
2.5.5

Fixing a WARN_ON caused by smp_call_function_any() when irq is disabled,
because of changes made in the patch
('cpufreq: powernv: Ramp-down global pstate slower than local-pstate')
https://patchwork.ozlabs.org/patch/612058/

 WARNING: CPU: 0 PID: 4 at kernel/smp.c:291
smp_call_function_single+0x170/0x180

 Call Trace:
 [c0000007f648f9f0] [c0000007f648fa90] 0xc0000007f648fa90 (unreliable)
 [c0000007f648fa30] [c0000000001430e0] smp_call_function_any+0x170/0x1c0
 [c0000007f648fa90] [c0000000007b4b00]
powernv_cpufreq_target_index+0xe0/0x250
 [c0000007f648fb00] [c0000000007ac9dc]
__cpufreq_driver_target+0x20c/0x3d0
 [c0000007f648fbc0] [c0000000007b1b4c] od_dbs_timer+0xcc/0x260
 [c0000007f648fc10] [c0000000007b3024] dbs_work_handler+0x54/0xa0
 [c0000007f648fc50] [c0000000000c49a8] process_one_work+0x1d8/0x590
 [c0000007f648fce0] [c0000000000c4e08] worker_thread+0xa8/0x660
 [c0000007f648fd80] [c0000000000cca88] kthread+0x108/0x130
 [c0000007f648fe30] [c0000000000095e8] ret_from_kernel_thread+0x5c/0x74

Moving smp_call_function_any() out of the critical section and changing
irq safe spinlocks to normal spinlocks.

Reported-by: Abdul Haleem <redacted>
Signed-off-by: Akshay Adiga <redacted>
---
Patch is based on Rafael's linux-next
 drivers/cpufreq/powernv-cpufreq.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index 144c732..1f0e20c 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c

@@ -581,9 +581,10 @@ void gpstate_timer_handler(unsigned long data)
 	gpstates->last_gpstate = freq_data.gpstate_id;
 	gpstates->last_lpstate = freq_data.pstate_id;
 
+	spin_unlock(&gpstates->gpstate_lock);
+
 	/* Timer may get migrated to a different cpu on cpu hot unplug */
 	smp_call_function_any(policy->cpus, set_pstate, &freq_data, 1);
-	spin_unlock(&gpstates->gpstate_lock);
 }
 
 /*

@@ -596,7 +597,6 @@ static int powernv_cpufreq_target_index(struct cpufreq_policy *policy,
 {
 	struct powernv_smp_call_data freq_data;
 	unsigned int cur_msec, gpstate_id;
-	unsigned long flags;
 	struct global_pstate_info *gpstates = policy->driver_data;
 
 	if (unlikely(rebooting) && new_index != get_nominal_index())

@@ -607,7 +607,7 @@ static int powernv_cpufreq_target_index(struct cpufreq_policy *policy,
 
 	cur_msec = jiffies_to_msecs(get_jiffies_64());
 
-	spin_lock_irqsave(&gpstates->gpstate_lock, flags);
+	spin_lock(&gpstates->gpstate_lock);
 	freq_data.pstate_id = powernv_freqs[new_index].driver_data;
 
 	if (!gpstates->last_sampled_time) {

@@ -654,13 +654,14 @@ gpstates_done:
 	gpstates->last_gpstate = freq_data.gpstate_id;
 	gpstates->last_lpstate = freq_data.pstate_id;
 
+	spin_unlock(&gpstates->gpstate_lock);
+
 	/*
 	 * Use smp_call_function to send IPI and execute the
 	 * mtspr on target CPU.  We could do that without IPI
 	 * if current CPU is within policy->cpus (core)
 	 */
 	smp_call_function_any(policy->cpus, set_pstate, &freq_data, 1);
-	spin_unlock_irqrestore(&gpstates->gpstate_lock, flags);
 	return 0;
 }
 

-- 
2.5.5

On 03-05-16, 15:10, Akshay Adiga wrote:

You don't necessarily have to write 'what you are doing' in the commit log, but
tell us why you are doing that.

Please explain, why is this changed and why will things continue to work
without this.

-- 
viresh

Hi Viresh,

On 05/03/2016 05:19 PM, Viresh Kumar wrote:

On 03-05-16, 15:10, Akshay Adiga wrote:

quoted

Fixing a WARN_ON caused by smp_call_function_any() when irq is disabled,
because of changes made in the patch
('cpufreq: powernv: Ramp-down global pstate slower than local-pstate')
https://patchwork.ozlabs.org/patch/612058/

  WARNING: CPU: 0 PID: 4 at kernel/smp.c:291
smp_call_function_single+0x170/0x180

  Call Trace:
  [c0000007f648f9f0] [c0000007f648fa90] 0xc0000007f648fa90 (unreliable)
  [c0000007f648fa30] [c0000000001430e0] smp_call_function_any+0x170/0x1c0
  [c0000007f648fa90] [c0000000007b4b00]
powernv_cpufreq_target_index+0xe0/0x250
  [c0000007f648fb00] [c0000000007ac9dc]
__cpufreq_driver_target+0x20c/0x3d0
  [c0000007f648fbc0] [c0000000007b1b4c] od_dbs_timer+0xcc/0x260
  [c0000007f648fc10] [c0000000007b3024] dbs_work_handler+0x54/0xa0
  [c0000007f648fc50] [c0000000000c49a8] process_one_work+0x1d8/0x590
  [c0000007f648fce0] [c0000000000c4e08] worker_thread+0xa8/0x660
  [c0000007f648fd80] [c0000000000cca88] kthread+0x108/0x130
  [c0000007f648fe30] [c0000000000095e8] ret_from_kernel_thread+0x5c/0x74

Moving smp_call_function_any() out of the critical section and changing
irq safe spinlocks to normal spinlocks.

Reported-by: Abdul Haleem <redacted>
Signed-off-by: Akshay Adiga <redacted>
---
Patch is based on Rafael's linux-next
  drivers/cpufreq/powernv-cpufreq.c | 9 +++++----
  1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/cpufreq/powernv-cpufreq.c b/drivers/cpufreq/powernv-cpufreq.c
index 144c732..1f0e20c 100644
--- a/drivers/cpufreq/powernv-cpufreq.c
+++ b/drivers/cpufreq/powernv-cpufreq.c

@@ -581,9 +581,10 @@ void gpstate_timer_handler(unsigned long data)
  	gpstates->last_gpstate = freq_data.gpstate_id;
  	gpstates->last_lpstate = freq_data.pstate_id;
  
+	spin_unlock(&gpstates->gpstate_lock);
+
  	/* Timer may get migrated to a different cpu on cpu hot unplug */
  	smp_call_function_any(policy->cpus, set_pstate, &freq_data, 1);
-	spin_unlock(&gpstates->gpstate_lock);
  }
  
  /*

@@ -596,7 +597,6 @@ static int powernv_cpufreq_target_index(struct cpufreq_policy *policy,
  {
  	struct powernv_smp_call_data freq_data;
  	unsigned int cur_msec, gpstate_id;
-	unsigned long flags;
  	struct global_pstate_info *gpstates = policy->driver_data;
  
  	if (unlikely(rebooting) && new_index != get_nominal_index())

@@ -607,7 +607,7 @@ static int powernv_cpufreq_target_index(struct cpufreq_policy *policy,
  
  	cur_msec = jiffies_to_msecs(get_jiffies_64());
  
-	spin_lock_irqsave(&gpstates->gpstate_lock, flags);
+	spin_lock(&gpstates->gpstate_lock);

You don't necessarily have to write 'what you are doing' in the commit log, but
tell us why you are doing that.

Please explain, why is this changed and why will things continue to work
without this.

Thanks for reviewing. I have tried to convey that in the first line of commit message,

"WARN_ON caused by smp_call_function_any() when irq is disabled,
because of changes made in the patch"

I see, i have not explained why i am changing irq safe spinlock to normal spinlock.
will add some explanation.