[3/3] drm/i915/selftests: avoid bogus maybe-uninitialized warning

Message ID 20200527140526.1458215-3-arnd@arndb.de
State New
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Series
  • [1/3] drm/i915/pmu: avoid an maybe-uninitialized warning
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Commit Message

Arnd Bergmann May 27, 2020, 2:05 p.m.
gcc has a problem following values through IS_ERR/PTR_ERR macros,
leading to a false-positive warning in allmodconfig, with any
compiler version:

In file included from drivers/gpu/drm/i915/gt/intel_lrc.c:5892:
drivers/gpu/drm/i915/gt/selftest_lrc.c: In function 'create_gpr_client.isra.0':
drivers/gpu/drm/i915/gt/selftest_lrc.c:2902:23: error: 'rq' may be used uninitialized in this function [-Werror=maybe-uninitialized]

This one is hard to avoid without impairing readability or adding a
bugus NULL pointer.

Fixes: c92724de6db1 ("drm/i915/selftests: Try to detect rollback during batchbuffer preemption")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>

---
 drivers/gpu/drm/i915/gt/selftest_lrc.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

-- 
2.26.2

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Comments

Chris Wilson May 27, 2020, 3:47 p.m. | #1
Quoting Arnd Bergmann (2020-05-27 15:05:10)
> gcc has a problem following values through IS_ERR/PTR_ERR macros,

> leading to a false-positive warning in allmodconfig, with any

> compiler version:

> 

> In file included from drivers/gpu/drm/i915/gt/intel_lrc.c:5892:

> drivers/gpu/drm/i915/gt/selftest_lrc.c: In function 'create_gpr_client.isra.0':

> drivers/gpu/drm/i915/gt/selftest_lrc.c:2902:23: error: 'rq' may be used uninitialized in this function [-Werror=maybe-uninitialized]

> 

> This one is hard to avoid without impairing readability or adding a

> bugus NULL pointer.

> 

> Fixes: c92724de6db1 ("drm/i915/selftests: Try to detect rollback during batchbuffer preemption")

> Signed-off-by: Arnd Bergmann <arnd@arndb.de>

> ---

>  drivers/gpu/drm/i915/gt/selftest_lrc.c | 21 +++++++++++++--------

>  1 file changed, 13 insertions(+), 8 deletions(-)

> 

> diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c b/drivers/gpu/drm/i915/gt/selftest_lrc.c

> index 824f99c4cc7c..933c3f5adf0a 100644

> --- a/drivers/gpu/drm/i915/gt/selftest_lrc.c

> +++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c

> @@ -2908,23 +2908,25 @@ create_gpr_client(struct intel_engine_cs *engine,

>  

>         vma = i915_vma_instance(global->obj, ce->vm, NULL);

>         if (IS_ERR(vma)) {

> -               err = PTR_ERR(vma);

> +               rq = ERR_CAST(vma);

>                 goto out_ce;

>         }

>  

>         err = i915_vma_pin(vma, 0, 0, PIN_USER);

> -       if (err)

> +       if (err) {

> +               rq = ERR_PTR(err);

>                 goto out_ce;

> +       }

>  

>         batch = create_gpr_user(engine, vma, offset);

>         if (IS_ERR(batch)) {

> -               err = PTR_ERR(batch);

> +               rq = ERR_CAST(batch);

>                 goto out_vma;

>         }

>  

>         rq = intel_context_create_request(ce);

>         if (IS_ERR(rq)) {

> -               err = PTR_ERR(rq);

> +               rq = ERR_CAST(rq);

>                 goto out_batch;

>         }

>  

> @@ -2946,17 +2948,20 @@ create_gpr_client(struct intel_engine_cs *engine,

>         i915_vma_unlock(batch);

>         i915_vma_unpin(batch);

>  

> -       if (!err)

> +       if (!err) {

>                 i915_request_get(rq);

> -       i915_request_add(rq);

> -

> +               i915_request_add(rq);

> +       } else {

> +               i915_request_add(rq);

> +               rq = ERR_PTR(err);

> +       }

>  out_batch:

>         i915_vma_put(batch);

>  out_vma:

>         i915_vma_unpin(vma);

>  out_ce:

>         intel_context_put(ce);

> -       return err ? ERR_PTR(err) : rq;

> +       return rq;


Hmm, I've used this style a few times, so could do with some syntactic
refinement.

drivers/gpu/drm/i915/gem/i915_gem_userptr.c:    return err ? ERR_PTR(err) : mm->mn;
drivers/gpu/drm/i915/gt/selftest_hangcheck.c:   return err ? ERR_PTR(err) : rq;
drivers/gpu/drm/i915/gt/selftest_lrc.c: return err ? ERR_PTR(err) : rq;
drivers/gpu/drm/i915/selftests/i915_gem_gtt.c:  return err ? ERR_PTR(err) : rq;
drivers/gpu/drm/i915/selftests/i915_request.c:  return err ? ERR_PTR(err) : request;
drivers/gpu/drm/i915/selftests/igt_spinner.c:   return err ? ERR_PTR(err) : rq;
-Chris

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Patch

diff --git a/drivers/gpu/drm/i915/gt/selftest_lrc.c b/drivers/gpu/drm/i915/gt/selftest_lrc.c
index 824f99c4cc7c..933c3f5adf0a 100644
--- a/drivers/gpu/drm/i915/gt/selftest_lrc.c
+++ b/drivers/gpu/drm/i915/gt/selftest_lrc.c
@@ -2908,23 +2908,25 @@  create_gpr_client(struct intel_engine_cs *engine,
 
 	vma = i915_vma_instance(global->obj, ce->vm, NULL);
 	if (IS_ERR(vma)) {
-		err = PTR_ERR(vma);
+		rq = ERR_CAST(vma);
 		goto out_ce;
 	}
 
 	err = i915_vma_pin(vma, 0, 0, PIN_USER);
-	if (err)
+	if (err) {
+		rq = ERR_PTR(err);
 		goto out_ce;
+	}
 
 	batch = create_gpr_user(engine, vma, offset);
 	if (IS_ERR(batch)) {
-		err = PTR_ERR(batch);
+		rq = ERR_CAST(batch);
 		goto out_vma;
 	}
 
 	rq = intel_context_create_request(ce);
 	if (IS_ERR(rq)) {
-		err = PTR_ERR(rq);
+		rq = ERR_CAST(rq);
 		goto out_batch;
 	}
 
@@ -2946,17 +2948,20 @@  create_gpr_client(struct intel_engine_cs *engine,
 	i915_vma_unlock(batch);
 	i915_vma_unpin(batch);
 
-	if (!err)
+	if (!err) {
 		i915_request_get(rq);
-	i915_request_add(rq);
-
+		i915_request_add(rq);
+	} else {
+		i915_request_add(rq);
+		rq = ERR_PTR(err);
+	}
 out_batch:
 	i915_vma_put(batch);
 out_vma:
 	i915_vma_unpin(vma);
 out_ce:
 	intel_context_put(ce);
-	return err ? ERR_PTR(err) : rq;
+	return rq;
 }
 
 static int preempt_user(struct intel_engine_cs *engine,