[PATCH 0/3] drm/i915: Enable -Wsometimes-uninitialized

[PATCH 0/3] drm/i915: Enable -Wsometimes-uninitialized

[Nathan Chancellor]

Commit 46e2068081e9 ("drm/i915: Disable some extra clang warnings")
disabled -Wsometimes-uninitialized as noisy but there have been a few
fixes to clang that make the false positive rate fairly low so it should
be enabled to help catch obvious mistakes. The first two patches fix
revent instances of this warning then enables it for i915 like the rest
of the tree.

Cheers,
Nathan

Nathan Chancellor (3):
  drm/i915/selftests: Do not use import_obj uninitialized
  drm/i915/selftests: Always initialize err in
    igt_dmabuf_import_same_driver_lmem()
  drm/i915: Enable -Wsometimes-uninitialized

 drivers/gpu/drm/i915/Makefile                        | 1 -
 drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c | 7 ++++---
 2 files changed, 4 insertions(+), 4 deletions(-)


base-commit: fb43ebc83e069625cfeeb2490efc3ffa0013bfa4
-- 
2.33.0

[PATCH 1/3] drm/i915/selftests: Do not use import_obj uninitialized

[Nathan Chancellor]

Clang warns a couple of times:

drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c:63:6: warning:
variable 'import_obj' is used uninitialized whenever 'if' condition is
true [-Wsometimes-uninitialized]
        if (import != &obj->base) {
            ^~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c:80:22: note:
uninitialized use occurs here
        i915_gem_object_put(import_obj);
                            ^~~~~~~~~~
drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c:63:2: note: remove
the 'if' if its condition is always false
        if (import != &obj->base) {
        ^~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c:38:46: note:
initialize the variable 'import_obj' to silence this warning
        struct drm_i915_gem_object *obj, *import_obj;
                                                    ^
                                                     = NULL

Shuffle the import_obj initialization above these if statements so that
it is not used uninitialized.

Fixes: d7b2cb380b3a ("drm/i915/gem: Correct the locking and pin pattern for dma-buf (v8)")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c
index ffae7df5e4d7..532c7955b300 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c
@@ -59,13 +59,13 @@ static int igt_dmabuf_import_self(void *arg)
 		err = PTR_ERR(import);
 		goto out_dmabuf;
 	}
+	import_obj = to_intel_bo(import);
 
 	if (import != &obj->base) {
 		pr_err("i915_gem_prime_import created a new object!\n");
 		err = -EINVAL;
 		goto out_import;
 	}
-	import_obj = to_intel_bo(import);
 
 	i915_gem_object_lock(import_obj, NULL);
 	err = __i915_gem_object_get_pages(import_obj);
@@ -176,6 +176,7 @@ static int igt_dmabuf_import_same_driver(struct drm_i915_private *i915,
 		err = PTR_ERR(import);
 		goto out_dmabuf;
 	}
+	import_obj = to_intel_bo(import);
 
 	if (import == &obj->base) {
 		pr_err("i915_gem_prime_import reused gem object!\n");
@@ -183,8 +184,6 @@ static int igt_dmabuf_import_same_driver(struct drm_i915_private *i915,
 		goto out_import;
 	}
 
-	import_obj = to_intel_bo(import);
-
 	i915_gem_object_lock(import_obj, NULL);
 	err = __i915_gem_object_get_pages(import_obj);
 	if (err) {
-- 
2.33.0

[PATCH 2/3] drm/i915/selftests: Always initialize err in igt_dmabuf_import_same_driver_lmem()

[Nathan Chancellor]

Clang warns:

drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c:127:13: warning:
variable 'err' is used uninitialized whenever 'if' condition is false
[-Wsometimes-uninitialized]
        } else if (PTR_ERR(import) != -EOPNOTSUPP) {
                   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c:138:9: note:
uninitialized use occurs here
        return err;
               ^~~
drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c:127:9: note: remove
the 'if' if its condition is always true
        } else if (PTR_ERR(import) != -EOPNOTSUPP) {
               ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c:95:9: note:
initialize the variable 'err' to silence this warning
        int err;
               ^
                = 0

The test is expected to pass if i915_gem_prime_import() returns
-EOPNOTSUPP so initialize err to zero in this case.

Fixes: cdb35d1ed6d2 ("drm/i915/gem: Migrate to system at dma-buf attach time (v7)")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c
index 532c7955b300..4a6bb64c3a35 100644
--- a/drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c
+++ b/drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c
@@ -128,6 +128,8 @@ static int igt_dmabuf_import_same_driver_lmem(void *arg)
 		pr_err("i915_gem_prime_import failed with the wrong err=%ld\n",
 		       PTR_ERR(import));
 		err = PTR_ERR(import);
+	} else {
+		err = 0;
 	}
 
 	dma_buf_put(dmabuf);
-- 
2.33.0

[PATCH 3/3] drm/i915: Enable -Wsometimes-uninitialized

[Nathan Chancellor]

This warning helps catch uninitialized variables. It should have been
enabled at the same time as commit b2423184ac33 ("drm/i915: Enable
-Wuninitialized") but I did not realize they were disabled separately.
Enable it now that i915 is clean so that it stays that way.

Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 drivers/gpu/drm/i915/Makefile | 1 -
 1 file changed, 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index 642a5b5a1b81..335ba9f43d8f 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -19,7 +19,6 @@ subdir-ccflags-y += $(call cc-disable-warning, missing-field-initializers)
 subdir-ccflags-y += $(call cc-disable-warning, unused-but-set-variable)
 # clang warnings
 subdir-ccflags-y += $(call cc-disable-warning, sign-compare)
-subdir-ccflags-y += $(call cc-disable-warning, sometimes-uninitialized)
 subdir-ccflags-y += $(call cc-disable-warning, initializer-overrides)
 subdir-ccflags-y += $(call cc-disable-warning, frame-address)
 subdir-ccflags-$(CONFIG_DRM_I915_WERROR) += -Werror
-- 
2.33.0

Re: [PATCH 1/3] drm/i915/selftests: Do not use import_obj uninitialized

[Thomas Hellström]

On 8/25/21 12:54 AM, Nathan Chancellor wrote:
> Clang warns a couple of times:
>
> drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c:63:6: warning:
> variable 'import_obj' is used uninitialized whenever 'if' condition is
> true [-Wsometimes-uninitialized]
>          if (import != &obj->base) {
>              ^~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c:80:22: note:
> uninitialized use occurs here
>          i915_gem_object_put(import_obj);
>                              ^~~~~~~~~~
> drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c:63:2: note: remove
> the 'if' if its condition is always false
>          if (import != &obj->base) {
>          ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c:38:46: note:
> initialize the variable 'import_obj' to silence this warning
>          struct drm_i915_gem_object *obj, *import_obj;
>                                                      ^
>                                                       = NULL
>
> Shuffle the import_obj initialization above these if statements so that
> it is not used uninitialized.
>
> Fixes: d7b2cb380b3a ("drm/i915/gem: Correct the locking and pin pattern for dma-buf (v8)")
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Patch looks good to me.

Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>

Re: [PATCH 2/3] drm/i915/selftests: Always initialize err in igt_dmabuf_import_same_driver_lmem()

[Thomas Hellström]

On 8/25/21 12:54 AM, Nathan Chancellor wrote:
> Clang warns:
>
> drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c:127:13: warning:
> variable 'err' is used uninitialized whenever 'if' condition is false
> [-Wsometimes-uninitialized]
>          } else if (PTR_ERR(import) != -EOPNOTSUPP) {
>                     ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c:138:9: note:
> uninitialized use occurs here
>          return err;
>                 ^~~
> drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c:127:9: note: remove
> the 'if' if its condition is always true
>          } else if (PTR_ERR(import) != -EOPNOTSUPP) {
>                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c:95:9: note:
> initialize the variable 'err' to silence this warning
>          int err;
>                 ^
>                  = 0
>
> The test is expected to pass if i915_gem_prime_import() returns
> -EOPNOTSUPP so initialize err to zero in this case.
>
> Fixes: cdb35d1ed6d2 ("drm/i915/gem: Migrate to system at dma-buf attach time (v7)")
> Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Reviewed-by: Thomas Hellström <thomas.hellstrom@linux.intel.com>

Re: [PATCH 0/3] drm/i915: Enable -Wsometimes-uninitialized

[Nathan Chancellor]

On Tue, Aug 24, 2021 at 03:54:24PM -0700, Nathan Chancellor wrote:
> Commit 46e2068081e9 ("drm/i915: Disable some extra clang warnings")
> disabled -Wsometimes-uninitialized as noisy but there have been a few
> fixes to clang that make the false positive rate fairly low so it should
> be enabled to help catch obvious mistakes. The first two patches fix
> revent instances of this warning then enables it for i915 like the rest
> of the tree.
> 
> Cheers,
> Nathan
> 
> Nathan Chancellor (3):
>   drm/i915/selftests: Do not use import_obj uninitialized
>   drm/i915/selftests: Always initialize err in
>     igt_dmabuf_import_same_driver_lmem()
>   drm/i915: Enable -Wsometimes-uninitialized
> 
>  drivers/gpu/drm/i915/Makefile                        | 1 -
>  drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c | 7 ++++---
>  2 files changed, 4 insertions(+), 4 deletions(-)
> 
> 
> base-commit: fb43ebc83e069625cfeeb2490efc3ffa0013bfa4
> -- 
> 2.33.0
> 
> 

Ping, could this be picked up for an -rc as these are very clearly bugs?

Cheers,
Nathan

Re: [PATCH 3/3] drm/i915: Enable -Wsometimes-uninitialized

[Nick Desaulniers]

On Tue, Aug 24, 2021 at 3:54 PM Nathan Chancellor <nathan@kernel.org> wrote:
>
> This warning helps catch uninitialized variables. It should have been
> enabled at the same time as commit b2423184ac33 ("drm/i915: Enable
> -Wuninitialized") but I did not realize they were disabled separately.
> Enable it now that i915 is clean so that it stays that way.
>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>

Thanks for the series!
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

> ---
>  drivers/gpu/drm/i915/Makefile | 1 -
>  1 file changed, 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
> index 642a5b5a1b81..335ba9f43d8f 100644
> --- a/drivers/gpu/drm/i915/Makefile
> +++ b/drivers/gpu/drm/i915/Makefile
> @@ -19,7 +19,6 @@ subdir-ccflags-y += $(call cc-disable-warning, missing-field-initializers)
>  subdir-ccflags-y += $(call cc-disable-warning, unused-but-set-variable)
>  # clang warnings
>  subdir-ccflags-y += $(call cc-disable-warning, sign-compare)
> -subdir-ccflags-y += $(call cc-disable-warning, sometimes-uninitialized)
>  subdir-ccflags-y += $(call cc-disable-warning, initializer-overrides)
>  subdir-ccflags-y += $(call cc-disable-warning, frame-address)
>  subdir-ccflags-$(CONFIG_DRM_I915_WERROR) += -Werror
> --
> 2.33.0
>


-- 
Thanks,
~Nick Desaulniers

Re: [PATCH 0/3] drm/i915: Enable -Wsometimes-uninitialized

[Jani Nikula]

On Mon, 13 Sep 2021, Nathan Chancellor <nathan@kernel.org> wrote:
> On Tue, Aug 24, 2021 at 03:54:24PM -0700, Nathan Chancellor wrote:
>> Commit 46e2068081e9 ("drm/i915: Disable some extra clang warnings")
>> disabled -Wsometimes-uninitialized as noisy but there have been a few
>> fixes to clang that make the false positive rate fairly low so it should
>> be enabled to help catch obvious mistakes. The first two patches fix
>> revent instances of this warning then enables it for i915 like the rest
>> of the tree.
>> 
>> Cheers,
>> Nathan
>> 
>> Nathan Chancellor (3):
>>   drm/i915/selftests: Do not use import_obj uninitialized
>>   drm/i915/selftests: Always initialize err in
>>     igt_dmabuf_import_same_driver_lmem()
>>   drm/i915: Enable -Wsometimes-uninitialized
>> 
>>  drivers/gpu/drm/i915/Makefile                        | 1 -
>>  drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c | 7 ++++---
>>  2 files changed, 4 insertions(+), 4 deletions(-)
>> 
>> 
>> base-commit: fb43ebc83e069625cfeeb2490efc3ffa0013bfa4
>> -- 
>> 2.33.0
>> 
>> 
>
> Ping, could this be picked up for an -rc as these are very clearly bugs?

Thanks for the patches and review. Pushed to drm-intel-gt-next and
cherry-picked to drm-intel-fixes, header to -rc2.

BR,
Jani.


-- 
Jani Nikula, Intel Open Source Graphics Center

Re: [PATCH 0/3] drm/i915: Enable -Wsometimes-uninitialized

[Nathan Chancellor]

On Tue, Sep 14, 2021 at 08:10:14PM +0300, Jani Nikula wrote:
> On Mon, 13 Sep 2021, Nathan Chancellor <nathan@kernel.org> wrote:
> > On Tue, Aug 24, 2021 at 03:54:24PM -0700, Nathan Chancellor wrote:
> >> Commit 46e2068081e9 ("drm/i915: Disable some extra clang warnings")
> >> disabled -Wsometimes-uninitialized as noisy but there have been a few
> >> fixes to clang that make the false positive rate fairly low so it should
> >> be enabled to help catch obvious mistakes. The first two patches fix
> >> revent instances of this warning then enables it for i915 like the rest
> >> of the tree.
> >> 
> >> Cheers,
> >> Nathan
> >> 
> >> Nathan Chancellor (3):
> >>   drm/i915/selftests: Do not use import_obj uninitialized
> >>   drm/i915/selftests: Always initialize err in
> >>     igt_dmabuf_import_same_driver_lmem()
> >>   drm/i915: Enable -Wsometimes-uninitialized
> >> 
> >>  drivers/gpu/drm/i915/Makefile                        | 1 -
> >>  drivers/gpu/drm/i915/gem/selftests/i915_gem_dmabuf.c | 7 ++++---
> >>  2 files changed, 4 insertions(+), 4 deletions(-)
> >> 
> >> 
> >> base-commit: fb43ebc83e069625cfeeb2490efc3ffa0013bfa4
> >> -- 
> >> 2.33.0
> >> 
> >> 
> >
> > Ping, could this be picked up for an -rc as these are very clearly bugs?
> 
> Thanks for the patches and review. Pushed to drm-intel-gt-next and
> cherry-picked to drm-intel-fixes, header to -rc2.

Thanks a lot!

Cheers,
Nathan