[Intel-gfx] [PATCH] drm/i915/selftests: Fix uninitialized variable

[Intel-gfx] [PATCH] drm/i915/selftests: Fix uninitialized variable

[Aditya Swarup]

Static code analysis tool identified struct lrc_timestamp data as being
uninitialized and then data.ce[] is being checked for NULL/negative
value in the error path. Initializing data variable fixes the issue.

Cc: Matt Roper <matthew.d.roper@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Aditya Swarup <aditya.swarup@intel.com>
---
 drivers/gpu/drm/i915/gt/selftest_lrc.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c b/drivers/gpu/drm/i915/gt/selftest_lrc.c
index ccf9debacd90..9b75b3c77a5b 100644
--- a/drivers/gpu/drm/i915/gt/selftest_lrc.c
+++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c
@@ -4725,7 +4725,7 @@ static int live_lrc_timestamp(void *arg)
 {
 	struct intel_gt *gt = arg;
 	enum intel_engine_id id;
-	struct lrc_timestamp data;
+	struct lrc_timestamp data = { 0 };
 	const u32 poison[] = {
 		0,
 		S32_MAX,
-- 
2.25.0

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Re: [Intel-gfx] [PATCH] drm/i915/selftests: Fix uninitialized variable

[Jani Nikula]

On Tue, 03 Mar 2020, Aditya Swarup <aditya.swarup@intel.com> wrote:
> Static code analysis tool identified struct lrc_timestamp data as being
> uninitialized and then data.ce[] is being checked for NULL/negative
> value in the error path. Initializing data variable fixes the issue.
>
> Cc: Matt Roper <matthew.d.roper@intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Aditya Swarup <aditya.swarup@intel.com>
> ---
>  drivers/gpu/drm/i915/gt/selftest_lrc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> index ccf9debacd90..9b75b3c77a5b 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> @@ -4725,7 +4725,7 @@ static int live_lrc_timestamp(void *arg)
>  {
>  	struct intel_gt *gt = arg;
>  	enum intel_engine_id id;
> -	struct lrc_timestamp data;
> +	struct lrc_timestamp data = { 0 };

{} is preferred over {0}.

BR,
Jani.

>  	const u32 poison[] = {
>  		0,
>  		S32_MAX,

-- 
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Re: [Intel-gfx] [PATCH] drm/i915/selftests: Fix uninitialized variable

[Matt Roper]

On Tue, Mar 03, 2020 at 05:25:21PM +0200, Jani Nikula wrote:
> On Tue, 03 Mar 2020, Aditya Swarup <aditya.swarup@intel.com> wrote:
> > Static code analysis tool identified struct lrc_timestamp data as being
> > uninitialized and then data.ce[] is being checked for NULL/negative
> > value in the error path. Initializing data variable fixes the issue.
> >
> > Cc: Matt Roper <matthew.d.roper@intel.com>
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Signed-off-by: Aditya Swarup <aditya.swarup@intel.com>
> > ---
> >  drivers/gpu/drm/i915/gt/selftest_lrc.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> > index ccf9debacd90..9b75b3c77a5b 100644
> > --- a/drivers/gpu/drm/i915/gt/selftest_lrc.c
> > +++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> > @@ -4725,7 +4725,7 @@ static int live_lrc_timestamp(void *arg)
> >  {
> >  	struct intel_gt *gt = arg;
> >  	enum intel_engine_id id;
> > -	struct lrc_timestamp data;
> > +	struct lrc_timestamp data = { 0 };
> 
> {} is preferred over {0}.

Is there a reference for this (e.g., in the kernel coding style)?  I
thought this came up a couple years ago and the consensus was the other
way, although I could be misremembering.  Unless it's changed in a
recent standard, I think {} is only legal in C++, so using it in C code
is a gcc-ism?


Matt


> 
> BR,
> Jani.
> 
> >  	const u32 poison[] = {
> >  		0,
> >  		S32_MAX,
> 
> -- 
> Jani Nikula, Intel Open Source Graphics Center
> _______________________________________________
> Intel-gfx mailing list
> Intel-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Matt Roper
Graphics Software Engineer
VTT-OSGC Platform Enablement
Intel Corporation
(916) 356-2795
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Re: [Intel-gfx] [PATCH] drm/i915/selftests: Fix uninitialized variable

[Jani Nikula]

On Tue, 03 Mar 2020, Matt Roper <matthew.d.roper@intel.com> wrote:
> On Tue, Mar 03, 2020 at 05:25:21PM +0200, Jani Nikula wrote:
>> On Tue, 03 Mar 2020, Aditya Swarup <aditya.swarup@intel.com> wrote:
>> > -	struct lrc_timestamp data;
>> > +	struct lrc_timestamp data = { 0 };
>> 
>> {} is preferred over {0}.
>
> Is there a reference for this (e.g., in the kernel coding style)?  I
> thought this came up a couple years ago and the consensus was the other
> way, although I could be misremembering.  Unless it's changed in a
> recent standard, I think {} is only legal in C++, so using it in C code
> is a gcc-ism?

Both are widely used in the kernel. I think we've mostly converged to {}
in i915. Yes, it's a gcc-ism in C code, but the kernel is gcc, not
standard C.

I can't find a reference right now, but ISTR there are some warnings
issued in some cases with the {0} initializer, depending on the struct
and perhaps on the compiler.

Anyway, we're 71 to 9 in favor of {} in i915, so please go with that.

BR,
Jani.


-- 
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Re: [Intel-gfx] [PATCH] drm/i915/selftests: Fix uninitialized variable

[Jani Nikula]

On Wed, 04 Mar 2020, Jani Nikula <jani.nikula@linux.intel.com> wrote:
> On Tue, 03 Mar 2020, Matt Roper <matthew.d.roper@intel.com> wrote:
>> On Tue, Mar 03, 2020 at 05:25:21PM +0200, Jani Nikula wrote:
>>> On Tue, 03 Mar 2020, Aditya Swarup <aditya.swarup@intel.com> wrote:
>>> > -	struct lrc_timestamp data;
>>> > +	struct lrc_timestamp data = { 0 };
>>> 
>>> {} is preferred over {0}.
>>
>> Is there a reference for this (e.g., in the kernel coding style)?  I
>> thought this came up a couple years ago and the consensus was the other
>> way, although I could be misremembering.  Unless it's changed in a
>> recent standard, I think {} is only legal in C++, so using it in C code
>> is a gcc-ism?
>
> Both are widely used in the kernel. I think we've mostly converged to {}
> in i915. Yes, it's a gcc-ism in C code, but the kernel is gcc, not
> standard C.
>
> I can't find a reference right now, but ISTR there are some warnings
> issued in some cases with the {0} initializer, depending on the struct
> and perhaps on the compiler.

Here's one [1].

BR,
Jani.


[1] http://patchwork.freedesktop.org/patch/msgid/20200304183654.GA9011@paulmck-ThinkPad-P72


-- 
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[Intel-gfx] ✗ Fi.CI.BUILD: failure for drm/i915/selftests: Fix uninitialized variable (rev2)

[Patchwork]

== Series Details ==

Series: drm/i915/selftests: Fix uninitialized variable (rev2)
URL   : https://patchwork.freedesktop.org/series/42194/
State : failure

== Summary ==

Applying: drm/i915/selftests: Fix uninitialized variable
Using index info to reconstruct a base tree...
M	drivers/gpu/drm/i915/gt/selftest_lrc.c
Falling back to patching base and 3-way merge...
Auto-merging drivers/gpu/drm/i915/gt/selftest_lrc.c
CONFLICT (content): Merge conflict in drivers/gpu/drm/i915/gt/selftest_lrc.c
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch' to see the failed patch
Patch failed at 0001 drm/i915/selftests: Fix uninitialized variable
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

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Re: [Intel-gfx] [PATCH] drm/i915/selftests: Fix uninitialized variable

[Matt Roper]

On Tue, Mar 03, 2020 at 06:23:47AM -0800, Aditya Swarup wrote:
> Static code analysis tool identified struct lrc_timestamp data as being
> uninitialized and then data.ce[] is being checked for NULL/negative
> value in the error path. Initializing data variable fixes the issue.
> 
> Cc: Matt Roper <matthew.d.roper@intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Signed-off-by: Aditya Swarup <aditya.swarup@intel.com>

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>

> ---
>  drivers/gpu/drm/i915/gt/selftest_lrc.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> index ccf9debacd90..9b75b3c77a5b 100644
> --- a/drivers/gpu/drm/i915/gt/selftest_lrc.c
> +++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c
> @@ -4725,7 +4725,7 @@ static int live_lrc_timestamp(void *arg)
>  {
>  	struct intel_gt *gt = arg;
>  	enum intel_engine_id id;
> -	struct lrc_timestamp data;
> +	struct lrc_timestamp data = { 0 };
>  	const u32 poison[] = {
>  		0,
>  		S32_MAX,
> -- 
> 2.25.0
> 

-- 
Matt Roper
Graphics Software Engineer
VTT-OSGC Platform Enablement
Intel Corporation
(916) 356-2795
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