[PATCH] locking/ww-mutex: Fix uninitialized use of ret in test_aa()

[PATCH] locking/ww-mutex: Fix uninitialized use of ret in test_aa()

[Nathan Chancellor]

Clang warns:

kernel/locking/test-ww_mutex.c:138:7: error: variable 'ret' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
                if (!ww_mutex_trylock(&mutex, &ctx)) {
                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/locking/test-ww_mutex.c:172:9: note: uninitialized use occurs here
        return ret;
               ^~~
kernel/locking/test-ww_mutex.c:138:3: note: remove the 'if' if its condition is always false
                if (!ww_mutex_trylock(&mutex, &ctx)) {
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/locking/test-ww_mutex.c:125:9: note: initialize the variable 'ret' to silence this warning
        int ret;
               ^
                = 0
1 error generated.

Assign !ww_mutex_trylock(...) to ret so that it is always initialized.

Fixes: 12235da8c80a ("kernel/locking: Add context to ww_mutex_trylock()")
Link: https://github.com/ClangBuiltLinux/linux/issues/1463
Reported-by: "kernelci.org bot" <bot@kernelci.org>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
---
 kernel/locking/test-ww_mutex.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
index d63ac411f367..353004155d65 100644
--- a/kernel/locking/test-ww_mutex.c
+++ b/kernel/locking/test-ww_mutex.c
@@ -135,7 +135,8 @@ static int test_aa(bool trylock)
 			goto out;
 		}
 	} else {
-		if (!ww_mutex_trylock(&mutex, &ctx)) {
+		ret = !ww_mutex_trylock(&mutex, &ctx);
+		if (ret) {
 			pr_err("%s: initial trylock failed!\n", __func__);
 			goto out;
 		}

base-commit: 12235da8c80a1f9909008e4ca6036d5772b81192
-- 
2.33.0.514.g99c99ed825

Re: [PATCH] locking/ww-mutex: Fix uninitialized use of ret in test_aa()

[Waiman Long]

On 9/22/21 10:58 AM, Nathan Chancellor wrote:
> Clang warns:
>
> kernel/locking/test-ww_mutex.c:138:7: error: variable 'ret' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
>                  if (!ww_mutex_trylock(&mutex, &ctx)) {
>                      ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> kernel/locking/test-ww_mutex.c:172:9: note: uninitialized use occurs here
>          return ret;
>                 ^~~
> kernel/locking/test-ww_mutex.c:138:3: note: remove the 'if' if its condition is always false
>                  if (!ww_mutex_trylock(&mutex, &ctx)) {
>                  ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> kernel/locking/test-ww_mutex.c:125:9: note: initialize the variable 'ret' to silence this warning
>          int ret;
>                 ^
>                  = 0
> 1 error generated.
>
> Assign !ww_mutex_trylock(...) to ret so that it is always initialized.
>
> Fixes: 12235da8c80a ("kernel/locking: Add context to ww_mutex_trylock()")
> Link: https://github.com/ClangBuiltLinux/linux/issues/1463
> Reported-by: "kernelci.org bot" <bot@kernelci.org>
> Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
> Signed-off-by: Nathan Chancellor <nathan@kernel.org>
> ---
>   kernel/locking/test-ww_mutex.c | 3 ++-
>   1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
> index d63ac411f367..353004155d65 100644
> --- a/kernel/locking/test-ww_mutex.c
> +++ b/kernel/locking/test-ww_mutex.c
> @@ -135,7 +135,8 @@ static int test_aa(bool trylock)
>   			goto out;
>   		}
>   	} else {
> -		if (!ww_mutex_trylock(&mutex, &ctx)) {
> +		ret = !ww_mutex_trylock(&mutex, &ctx);
> +		if (ret) {
>   			pr_err("%s: initial trylock failed!\n", __func__);
>   			goto out;
>   		}
>
> base-commit: 12235da8c80a1f9909008e4ca6036d5772b81192

I was a bit confused by this patch at the beginning and then realized 
that it was supposed to be applied on top of the tip true, not the 
current mainline kernel.

Anyway, it looks good to me

Acked-by: Waiman Long <longman@redhat.com>

[tip: locking/core] locking/ww-mutex: Fix uninitialized use of ret in test_aa()

[tip-bot2 for Nathan Chancellor]

The following commit has been merged into the locking/core branch of tip:

Commit-ID:     1415b49bcd321bca7347f43f8b269c91ec46d1dc
Gitweb:        https://git.kernel.org/tip/1415b49bcd321bca7347f43f8b269c91ec46d1dc
Author:        Nathan Chancellor <nathan@kernel.org>
AuthorDate:    Wed, 22 Sep 2021 07:58:22 -07:00
Committer:     Peter Zijlstra <peterz@infradead.org>
CommitterDate: Fri, 01 Oct 2021 13:57:49 +02:00

locking/ww-mutex: Fix uninitialized use of ret in test_aa()

Clang warns:

kernel/locking/test-ww_mutex.c:138:7: error: variable 'ret' is used uninitialized whenever 'if' condition is true [-Werror,-Wsometimes-uninitialized]
                if (!ww_mutex_trylock(&mutex, &ctx)) {
                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/locking/test-ww_mutex.c:172:9: note: uninitialized use occurs here
        return ret;
               ^~~
kernel/locking/test-ww_mutex.c:138:3: note: remove the 'if' if its condition is always false
                if (!ww_mutex_trylock(&mutex, &ctx)) {
                ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
kernel/locking/test-ww_mutex.c:125:9: note: initialize the variable 'ret' to silence this warning
        int ret;
               ^
                = 0
1 error generated.

Assign !ww_mutex_trylock(...) to ret so that it is always initialized.

Fixes: 12235da8c80a ("kernel/locking: Add context to ww_mutex_trylock()")
Reported-by: "kernelci.org bot" <bot@kernelci.org>
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Nathan Chancellor <nathan@kernel.org>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Waiman Long <longman@redhat.com>
Link: https://lore.kernel.org/r/20210922145822.3935141-1-nathan@kernel.org
---
 kernel/locking/test-ww_mutex.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/locking/test-ww_mutex.c b/kernel/locking/test-ww_mutex.c
index d63ac41..3530041 100644
--- a/kernel/locking/test-ww_mutex.c
+++ b/kernel/locking/test-ww_mutex.c
@@ -135,7 +135,8 @@ static int test_aa(bool trylock)
 			goto out;
 		}
 	} else {
-		if (!ww_mutex_trylock(&mutex, &ctx)) {
+		ret = !ww_mutex_trylock(&mutex, &ctx);
+		if (ret) {
 			pr_err("%s: initial trylock failed!\n", __func__);
 			goto out;
 		}