From: Peter Zijlstra <peterz@infradead.org>
To: Arnd Bergmann <arnd@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>,
Matthew Wilcox <willy@infradead.org>,
Ingo Molnar <mingo@kernel.org>, Will Deacon <will@kernel.org>,
Will Deacon <will.deacon@arm.com>,
Thomas Gleixner <tglx@linutronix.de>,
Waiman Long <longman@redhat.com>,
Nicholas Piggin <npiggin@gmail.com>,
Michael Ellerman <mpe@ellerman.id.au>,
Herbert Xu <herbert@gondor.apana.org.au>,
linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] qspinlock: use signed temporaries for cmpxchg
Date: Mon, 26 Oct 2020 18:10:45 +0100 [thread overview]
Message-ID: <20201026171045.GU2611@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20201026165807.3724647-1-arnd@kernel.org>
On Mon, Oct 26, 2020 at 05:57:51PM +0100, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
>
> When building with W=2, the build log is flooded with
>
> include/asm-generic/qrwlock.h:65:56: warning: pointer targets in passing argument 2 of 'atomic_try_cmpxchg_acquire' differ in signedness [-Wpointer-sign]
> include/asm-generic/qrwlock.h:92:53: warning: pointer targets in passing argument 2 of 'atomic_try_cmpxchg_acquire' differ in signedness [-Wpointer-sign]
> include/asm-generic/qspinlock.h:68:55: warning: pointer targets in passing argument 2 of 'atomic_try_cmpxchg_acquire' differ in signedness [-Wpointer-sign]
> include/asm-generic/qspinlock.h:82:52: warning: pointer targets in passing argument 2 of 'atomic_try_cmpxchg_acquire' differ in signedness [-Wpointer-sign]
>
> The atomics are built on top of signed integers, but the caller
> doesn't actually care. Just use signed types as well.
>
Yuck, no. This is actively wrong. All that code very much wants u32.
next prev parent reply other threads:[~2020-10-26 17:48 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-10-26 16:57 [PATCH] qspinlock: use signed temporaries for cmpxchg Arnd Bergmann
2020-10-26 17:10 ` Peter Zijlstra [this message]
2020-10-26 18:03 ` Waiman Long
2020-10-27 7:47 ` Peter Zijlstra
2020-10-27 8:33 ` Arnd Bergmann
2020-10-27 10:32 ` Peter Zijlstra
2020-10-27 13:38 ` David Laight
2020-10-27 16:22 ` Arnd Bergmann
2020-10-27 17:34 ` Peter Zijlstra
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