Re: [PATCH] drm/i915/pmu: avoid -Wmaybe-uninitialized warning

2018-03-13 Thread Arnd Bergmann
On Tue, Mar 13, 2018 at 1:31 PM, Chris Wilson  wrote:
> Quoting Arnd Bergmann (2018-03-13 12:08:29)
>> The conditional spinlock confuses gcc into thinking the 'flags' value
>> might contain uninitialized data:
>>
>> drivers/gpu/drm/i915/i915_pmu.c: In function '__i915_pmu_event_read':
>> arch/x86/include/asm/paravirt_types.h:573:3: error: 'flags' may be used 
>> uninitialized in this function [-Werror=maybe-uninitialized]
>>
>> The code is correct, but it's easy to see how the compiler gets confused
>> here. This avoids the problem by pulling the lock outside of the function
>> into its only caller.
>>
>> Fixes: 1fe699e30113 ("drm/i915/pmu: Fix sleep under atomic in RC6 readout")
>> Signed-off-by: Arnd Bergmann 
>> ---
>>  drivers/gpu/drm/i915/i915_pmu.c | 25 ++---
>>  1 file changed, 10 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_pmu.c 
>> b/drivers/gpu/drm/i915/i915_pmu.c
>> index 4bc7aefa9541..2c8c705d1f18 100644
>> --- a/drivers/gpu/drm/i915/i915_pmu.c
>> +++ b/drivers/gpu/drm/i915/i915_pmu.c
>> @@ -415,7 +415,6 @@ static u64 __get_rc6(struct drm_i915_private *i915)
>>  static u64 get_rc6(struct drm_i915_private *i915, bool locked)
>
> bool locked is now unused, right?

Right, removing it now.

>> -   val = get_rc6(i915, locked);
>> -   break;
>> +   if (!locked) {
>> +   unsigned long flags;
>> +
>> +   spin_lock_irqsave(>pmu.lock, flags);
>> +   val = get_rc6(i915, locked);
>> +   spin_unlock_irqrestore(>pmu.lock, 
>> flags);
>> +   break;
>> +   } else {
>> +   val = get_rc6(i915, locked);
>> +   }
>
> break is now on one path only; should be here.

Fixed as well. I'll wait a bit for more comments before resending.

Thanks for the review!

 Arnd


Re: [PATCH] drm/i915/pmu: avoid -Wmaybe-uninitialized warning

2018-03-13 Thread Arnd Bergmann
On Tue, Mar 13, 2018 at 1:31 PM, Chris Wilson  wrote:
> Quoting Arnd Bergmann (2018-03-13 12:08:29)
>> The conditional spinlock confuses gcc into thinking the 'flags' value
>> might contain uninitialized data:
>>
>> drivers/gpu/drm/i915/i915_pmu.c: In function '__i915_pmu_event_read':
>> arch/x86/include/asm/paravirt_types.h:573:3: error: 'flags' may be used 
>> uninitialized in this function [-Werror=maybe-uninitialized]
>>
>> The code is correct, but it's easy to see how the compiler gets confused
>> here. This avoids the problem by pulling the lock outside of the function
>> into its only caller.
>>
>> Fixes: 1fe699e30113 ("drm/i915/pmu: Fix sleep under atomic in RC6 readout")
>> Signed-off-by: Arnd Bergmann 
>> ---
>>  drivers/gpu/drm/i915/i915_pmu.c | 25 ++---
>>  1 file changed, 10 insertions(+), 15 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_pmu.c 
>> b/drivers/gpu/drm/i915/i915_pmu.c
>> index 4bc7aefa9541..2c8c705d1f18 100644
>> --- a/drivers/gpu/drm/i915/i915_pmu.c
>> +++ b/drivers/gpu/drm/i915/i915_pmu.c
>> @@ -415,7 +415,6 @@ static u64 __get_rc6(struct drm_i915_private *i915)
>>  static u64 get_rc6(struct drm_i915_private *i915, bool locked)
>
> bool locked is now unused, right?

Right, removing it now.

>> -   val = get_rc6(i915, locked);
>> -   break;
>> +   if (!locked) {
>> +   unsigned long flags;
>> +
>> +   spin_lock_irqsave(>pmu.lock, flags);
>> +   val = get_rc6(i915, locked);
>> +   spin_unlock_irqrestore(>pmu.lock, 
>> flags);
>> +   break;
>> +   } else {
>> +   val = get_rc6(i915, locked);
>> +   }
>
> break is now on one path only; should be here.

Fixed as well. I'll wait a bit for more comments before resending.

Thanks for the review!

 Arnd


Re: [PATCH] drm/i915/pmu: avoid -Wmaybe-uninitialized warning

2018-03-13 Thread Chris Wilson
Quoting Arnd Bergmann (2018-03-13 12:08:29)
> The conditional spinlock confuses gcc into thinking the 'flags' value
> might contain uninitialized data:
> 
> drivers/gpu/drm/i915/i915_pmu.c: In function '__i915_pmu_event_read':
> arch/x86/include/asm/paravirt_types.h:573:3: error: 'flags' may be used 
> uninitialized in this function [-Werror=maybe-uninitialized]
> 
> The code is correct, but it's easy to see how the compiler gets confused
> here. This avoids the problem by pulling the lock outside of the function
> into its only caller.
> 
> Fixes: 1fe699e30113 ("drm/i915/pmu: Fix sleep under atomic in RC6 readout")
> Signed-off-by: Arnd Bergmann 
> ---
>  drivers/gpu/drm/i915/i915_pmu.c | 25 ++---
>  1 file changed, 10 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
> index 4bc7aefa9541..2c8c705d1f18 100644
> --- a/drivers/gpu/drm/i915/i915_pmu.c
> +++ b/drivers/gpu/drm/i915/i915_pmu.c
> @@ -415,7 +415,6 @@ static u64 __get_rc6(struct drm_i915_private *i915)
>  static u64 get_rc6(struct drm_i915_private *i915, bool locked)

bool locked is now unused, right?

>  {
>  #if IS_ENABLED(CONFIG_PM)
> -   unsigned long flags;
> u64 val;
>  
> if (intel_runtime_pm_get_if_in_use(i915)) {
> @@ -428,18 +427,12 @@ static u64 get_rc6(struct drm_i915_private *i915, bool 
> locked)
>  * previously.
>  */
>  
> -   if (!locked)
> -   spin_lock_irqsave(>pmu.lock, flags);
> -
> if (val >= i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur) 
> {
> i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur = 0;
> i915->pmu.sample[__I915_SAMPLE_RC6].cur = val;
> } else {
> val = 
> i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur;
> }
> -
> -   if (!locked)
> -   spin_unlock_irqrestore(>pmu.lock, flags);
> } else {
> struct pci_dev *pdev = i915->drm.pdev;
> struct device *kdev = >dev;
> @@ -452,9 +445,6 @@ static u64 get_rc6(struct drm_i915_private *i915, bool 
> locked)
>  * on top of the last known real value, as the approximated 
> RC6
>  * counter value.
>  */
> -   if (!locked)
> -   spin_lock_irqsave(>pmu.lock, flags);
> -
> spin_lock_irqsave(>power.lock, flags2);
>  
> if (!i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur)
> @@ -470,9 +460,6 @@ static u64 get_rc6(struct drm_i915_private *i915, bool 
> locked)
> val = jiffies_to_nsecs(val);
> val += i915->pmu.sample[__I915_SAMPLE_RC6].cur;
> i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur = val;
> -
> -   if (!locked)
> -   spin_unlock_irqrestore(>pmu.lock, flags);
> }
>  
> return val;
> @@ -519,8 +506,16 @@ static u64 __i915_pmu_event_read(struct perf_event 
> *event, bool locked)
> val = count_interrupts(i915);
> break;
> case I915_PMU_RC6_RESIDENCY:
> -   val = get_rc6(i915, locked);
> -   break;
> +   if (!locked) {
> +   unsigned long flags;
> +
> +   spin_lock_irqsave(>pmu.lock, flags);
> +   val = get_rc6(i915, locked);
> +   spin_unlock_irqrestore(>pmu.lock, 
> flags);
> +   break;
> +   } else {
> +   val = get_rc6(i915, locked);
> +   }

break is now on one path only; should be here.
-Chris


Re: [PATCH] drm/i915/pmu: avoid -Wmaybe-uninitialized warning

2018-03-13 Thread Chris Wilson
Quoting Arnd Bergmann (2018-03-13 12:08:29)
> The conditional spinlock confuses gcc into thinking the 'flags' value
> might contain uninitialized data:
> 
> drivers/gpu/drm/i915/i915_pmu.c: In function '__i915_pmu_event_read':
> arch/x86/include/asm/paravirt_types.h:573:3: error: 'flags' may be used 
> uninitialized in this function [-Werror=maybe-uninitialized]
> 
> The code is correct, but it's easy to see how the compiler gets confused
> here. This avoids the problem by pulling the lock outside of the function
> into its only caller.
> 
> Fixes: 1fe699e30113 ("drm/i915/pmu: Fix sleep under atomic in RC6 readout")
> Signed-off-by: Arnd Bergmann 
> ---
>  drivers/gpu/drm/i915/i915_pmu.c | 25 ++---
>  1 file changed, 10 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_pmu.c b/drivers/gpu/drm/i915/i915_pmu.c
> index 4bc7aefa9541..2c8c705d1f18 100644
> --- a/drivers/gpu/drm/i915/i915_pmu.c
> +++ b/drivers/gpu/drm/i915/i915_pmu.c
> @@ -415,7 +415,6 @@ static u64 __get_rc6(struct drm_i915_private *i915)
>  static u64 get_rc6(struct drm_i915_private *i915, bool locked)

bool locked is now unused, right?

>  {
>  #if IS_ENABLED(CONFIG_PM)
> -   unsigned long flags;
> u64 val;
>  
> if (intel_runtime_pm_get_if_in_use(i915)) {
> @@ -428,18 +427,12 @@ static u64 get_rc6(struct drm_i915_private *i915, bool 
> locked)
>  * previously.
>  */
>  
> -   if (!locked)
> -   spin_lock_irqsave(>pmu.lock, flags);
> -
> if (val >= i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur) 
> {
> i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur = 0;
> i915->pmu.sample[__I915_SAMPLE_RC6].cur = val;
> } else {
> val = 
> i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur;
> }
> -
> -   if (!locked)
> -   spin_unlock_irqrestore(>pmu.lock, flags);
> } else {
> struct pci_dev *pdev = i915->drm.pdev;
> struct device *kdev = >dev;
> @@ -452,9 +445,6 @@ static u64 get_rc6(struct drm_i915_private *i915, bool 
> locked)
>  * on top of the last known real value, as the approximated 
> RC6
>  * counter value.
>  */
> -   if (!locked)
> -   spin_lock_irqsave(>pmu.lock, flags);
> -
> spin_lock_irqsave(>power.lock, flags2);
>  
> if (!i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur)
> @@ -470,9 +460,6 @@ static u64 get_rc6(struct drm_i915_private *i915, bool 
> locked)
> val = jiffies_to_nsecs(val);
> val += i915->pmu.sample[__I915_SAMPLE_RC6].cur;
> i915->pmu.sample[__I915_SAMPLE_RC6_ESTIMATED].cur = val;
> -
> -   if (!locked)
> -   spin_unlock_irqrestore(>pmu.lock, flags);
> }
>  
> return val;
> @@ -519,8 +506,16 @@ static u64 __i915_pmu_event_read(struct perf_event 
> *event, bool locked)
> val = count_interrupts(i915);
> break;
> case I915_PMU_RC6_RESIDENCY:
> -   val = get_rc6(i915, locked);
> -   break;
> +   if (!locked) {
> +   unsigned long flags;
> +
> +   spin_lock_irqsave(>pmu.lock, flags);
> +   val = get_rc6(i915, locked);
> +   spin_unlock_irqrestore(>pmu.lock, 
> flags);
> +   break;
> +   } else {
> +   val = get_rc6(i915, locked);
> +   }

break is now on one path only; should be here.
-Chris