* [PATCH] drm/i915/pmu: avoid -Wmaybe-uninitialized warning
@ 2018-03-13 12:08 Arnd Bergmann
2018-03-13 12:31 ` Chris Wilson
0 siblings, 1 reply; 3+ messages in thread
From: Arnd Bergmann @ 2018-03-13 12:08 UTC (permalink / raw)
To: Jani Nikula, Joonas Lahtinen, Rodrigo Vivi, David Airlie
Cc: Arnd Bergmann, Tvrtko Ursulin, Chris Wilson, Michal Wajdeczko,
intel-gfx, dri-devel, linux-kernel
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 <arnd@arndb.de>
---
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)
{
#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(&i915->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(&i915->pmu.lock, flags);
} else {
struct pci_dev *pdev = i915->drm.pdev;
struct device *kdev = &pdev->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(&i915->pmu.lock, flags);
-
spin_lock_irqsave(&kdev->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(&i915->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(&i915->pmu.lock, flags);
+ val = get_rc6(i915, locked);
+ spin_unlock_irqrestore(&i915->pmu.lock, flags);
+ break;
+ } else {
+ val = get_rc6(i915, locked);
+ }
}
}
--
2.9.0
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] drm/i915/pmu: avoid -Wmaybe-uninitialized warning
2018-03-13 12:08 [PATCH] drm/i915/pmu: avoid -Wmaybe-uninitialized warning Arnd Bergmann
@ 2018-03-13 12:31 ` Chris Wilson
2018-03-13 12:55 ` Arnd Bergmann
0 siblings, 1 reply; 3+ messages in thread
From: Chris Wilson @ 2018-03-13 12:31 UTC (permalink / raw)
To: Arnd Bergmann, Jani Nikula, Joonas Lahtinen, Rodrigo Vivi, David Airlie
Cc: Arnd Bergmann, Tvrtko Ursulin, Michal Wajdeczko, intel-gfx,
dri-devel, linux-kernel
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 <arnd@arndb.de>
> ---
> 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(&i915->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(&i915->pmu.lock, flags);
> } else {
> struct pci_dev *pdev = i915->drm.pdev;
> struct device *kdev = &pdev->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(&i915->pmu.lock, flags);
> -
> spin_lock_irqsave(&kdev->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(&i915->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(&i915->pmu.lock, flags);
> + val = get_rc6(i915, locked);
> + spin_unlock_irqrestore(&i915->pmu.lock, flags);
> + break;
> + } else {
> + val = get_rc6(i915, locked);
> + }
break is now on one path only; should be here.
-Chris
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] drm/i915/pmu: avoid -Wmaybe-uninitialized warning
2018-03-13 12:31 ` Chris Wilson
@ 2018-03-13 12:55 ` Arnd Bergmann
0 siblings, 0 replies; 3+ messages in thread
From: Arnd Bergmann @ 2018-03-13 12:55 UTC (permalink / raw)
To: Chris Wilson
Cc: Jani Nikula, Joonas Lahtinen, Rodrigo Vivi, David Airlie,
Tvrtko Ursulin, Michal Wajdeczko, Intel Graphics, dri-devel,
Linux Kernel Mailing List
On Tue, Mar 13, 2018 at 1:31 PM, Chris Wilson <chris@chris-wilson.co.uk> 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 <arnd@arndb.de>
>> ---
>> 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(&i915->pmu.lock, flags);
>> + val = get_rc6(i915, locked);
>> + spin_unlock_irqrestore(&i915->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
^ permalink raw reply [flat|nested] 3+ messages in thread
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2018-03-13 12:08 [PATCH] drm/i915/pmu: avoid -Wmaybe-uninitialized warning Arnd Bergmann
2018-03-13 12:31 ` Chris Wilson
2018-03-13 12:55 ` Arnd Bergmann
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