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From:   Nathan Chancellor <nathan@kernel.org>
To:     Peter Zijlstra <peterz@infradead.org>,
        Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>
Cc:     Waiman Long <longman@redhat.com>,
        Boqun Feng <boqun.feng@gmail.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        linux-kernel@vger.kernel.org, llvm@lists.linux.dev,
        Nathan Chancellor <nathan@kernel.org>,
        "kernelci.org bot" <bot@kernelci.org>,
        Stephen Rothwell <sfr@canb.auug.org.au>
Subject: [PATCH] locking/ww-mutex: Fix uninitialized use of ret in test_aa()
Date:   Wed, 22 Sep 2021 07:58:22 -0700
Message-Id: <20210922145822.3935141-1-nathan@kernel.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit
Precedence: bulk

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