linux-kernel - Re: [PATCH] selftests/rseq: fix kselftest Clang build warnings

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Message-ID: <63dd7222-99dc-8e11-3a51-b132e4115ac5@linuxfoundation.org>
Date:   Tue, 26 Sep 2023 14:39:27 -0600
From:   Shuah Khan <skhan@...uxfoundation.org>
To:     Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Justin Stitt <justinstitt@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Boqun Feng <boqun.feng@...il.com>,
        Shuah Khan <shuah@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Tom Rix <trix@...hat.com>
Cc:     linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        llvm@...ts.linux.dev, Shuah Khan <skhan@...uxfoundation.org>
Subject: Re: [PATCH] selftests/rseq: fix kselftest Clang build warnings

On 9/26/23 13:02, Mathieu Desnoyers wrote:
> On 9/26/23 08:20, Justin Stitt wrote:
>> Ping.
>>
>> Looking to get this patch and [1] slated for 6.7 which fixes some
>> kselftest builds on older kernels.
>>
>> On Wed, Sep 13, 2023 at 6:03 AM Justin Stitt <justinstitt@...gle.com> wrote:
>>>
>>> When building with Clang, I am getting many warnings from the selftests/rseq tree.
>>>
>>> Here's one such example from rseq tree:
>>> |  param_test.c:1234:10: error: address argument to atomic operation must be a pointer to _Atomic type ('intptr_t *' (aka 'long *') invalid)
>>> |   1234 |         while (!atomic_load(&args->percpu_list_ptr)) {}
>>> |        |                 ^           ~~~~~~~~~~~~~~~~~~~~~~
>>> |  /usr/local/google/home/justinstitt/repos/tc-build/build/llvm/final/lib/clang/18/include/stdatomic.h:140:29: note: expanded from macro 'atomic_load'
>>> |    140 | #define atomic_load(object) __c11_atomic_load(object, __ATOMIC_SEQ_CST)
>>> |        |                             ^                 ~~~~~~
>>>
>>> Use compiler builtins `__atomic_load_n()` and `__atomic_store_n()` with
>>> accompanying __ATOMIC_ACQUIRE and __ATOMIC_RELEASE, respectively. This
>>> will fix the warnings because the compiler builtins do not expect their
>>> arguments to have _Atomic type. This should also make TSAN happier.
>>>
>>> Link: https://github.com/ClangBuiltLinux/linux/issues/1698
>>> Link: https://github.com/ClangBuiltLinux/continuous-integration2/issues/61
>>> Suggested-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
>>> Signed-off-by: Justin Stitt <justinstitt@...gle.com>
> 
> Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> 
> Peter, should this go through tip ?
> 
> Shuah, should to go through selftests ?
> 

I can take this through selftests and apply it - hoping there
are no conflicts with what's in Peter's tree.

thanks,
-- Shuah