From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pj1-f48.google.com (mail-pj1-f48.google.com [209.85.216.48]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 169413DBD78 for ; Thu, 2 Apr 2026 13:08:01 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.216.48 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775135284; cv=none; b=VuclCak7SbJsaYma2A2TM5wbkA6AQNFQnEpe7RF6trIxtiorLX29k5LgdXqS3RHtcOrtsyrl3LBD7xyjW7ssgcNNJqrbU3+pGwH7RzL4hOD1b1wM5ysgxQS7nL90K3Trv1t1iatnWhUu7XVIlmo+uSyqxySw0fPseGtQxSK7ERk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1775135284; c=relaxed/simple; bh=J6KuSzBKCDeaYiVgmtuuUSqnvej1+MF06b183JPn5yo=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=Bdc5Y+Gj++AB4rhjYU+u6IcqzkWMB/gKx9cQsFWxX60J9j6BQjIqXkitfN2sNO+HgQAYkxodM+CklXU5IfSojwm71UIXuu8+/fBNRdOc5X1NpC27lkuD2v4iaGp5trP5ysXF13O8jqpGcb4c3uhKmKZT9pWSqSKuzdmF4GCRkqU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=PJY3Xeej; arc=none smtp.client-ip=209.85.216.48 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="PJY3Xeej" Received: by mail-pj1-f48.google.com with SMTP id 98e67ed59e1d1-35d94f4ee36so497398a91.3 for ; Thu, 02 Apr 2026 06:08:01 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1775135281; x=1775740081; darn=vger.kernel.org; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=KWxJTOWQkri5jmv5ZKMT+tNuIWsfKgbRVKTEMtbqloY=; b=PJY3XeejgWRIMXpyhMO+u6jxmLwxcfufASnNiIpFCkeNcvwAsithilHAfhY5wy/vng 3OIgjRGhBHlDo5N7PhFCoMz9TVsP5yETjR5N7Rh3OlGy17wuPY0IkACiql1W0ukMTSqo 4KvtkNtw4f3WQUJyfGvDBYgAX7NkxzjN7CDvbMU/GWg+T8UtV8yaT2+0UTb5iIAZrys9 clV/yGPMxreSzrM50jf83Q0/nyNXCMX0BSbHk8PawyfpLZbdrSkfZyovK97mRRnBNt3W pKYWlCXTMLNkGPJ/Sf4MSUpboNvn+sfYQcnjUa1aeRK6+dLoCAcQehPMWL8oFNC3pin4 1z7g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1775135281; x=1775740081; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-gg:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=KWxJTOWQkri5jmv5ZKMT+tNuIWsfKgbRVKTEMtbqloY=; b=NPCdnY5umapkCLpGnKlxzYUHOATPBWyb0jooTokdYJ5UXHpY7O7L5KLG7PgA9pp/c/ MzUhFcMaobb+/Py4fJQczD5DAfoVpKD9bcM22T/05121qDr67riAhRQ3Qkwr2PxCwg+O 7a2IM/bx/JYd28VsOcIfGWKvDy30XqtzKjE1jfb7aoEpoM6qPpRwmkSi2wjAmqz/ATTC buHmCQ8GIWJ1lbIE/iEdGzGJfX9R6oKUcNHXa+6QM3e1lgPOC75h3a5BRgGLkx6y47CN Ak3eoqvzTwR0X83RAT2mTLF9OnGQSBK6zRSv5J7lLOX4UInYSn4Y/iSWotAmf829oZ6j SlxQ== X-Forwarded-Encrypted: i=1; AJvYcCUoKqEt+keVVZRGTDg2Hgx4GVRnIfCDMjuywzBuA/FmhCVQGDdLBb+7v1qmDwBce3ut2/NAv1RZyhM/ofkF@vger.kernel.org X-Gm-Message-State: AOJu0YzNf6wK+XREQgxUXoeVSUuioiOXTeYvIXuO7d1/5CcMbjsk4/hs G/cqb460qNDBLH/sILzizyKGXrFm1sxBE5O4NsI2yiYyQxfk4kz04wZs X-Gm-Gg: AeBDieu06P8tyybqBgSKhWGVQmhRWbpoM/skHbH7OL3Dul48Z4vTka0OHhwNOuee862 ELBEeHGu+yx60cKIrdANx8hlt9/gg+0sw/3vnTvuYv5F2S8xDtSgpYO66kEROrhdSH7bKXG5pWv b81JnAnKI1+jm55X/25eyr4xA6g/N8s5JjMPYRVeLMaZyZ6tpqZfZfaNqDdTgTesUEPpldcfIss UPd1tJE1TrAF16eDYYvkdub4AIcCL6i0ASeP8VwftAaOrDfjEk2gJw3soNv2ZmEz7Wip2vO+bNL JPuNc9PLFg15Amfqr4xcCbNIyivcKzH2ANoE8UsO1+cyXxRMQ9wxKCLJtwDHvO5dBRYiFTufXwa a9nZzKtXoS+zCpFjV4YdA+ZO17+ta8dHCsdeOaRAGW1+2s9dYaUHllWJnAm6SmNPRygaVjchGh2 aDKMeBCMlpJgyLtBL9+ouoRM6fxco= X-Received: by 2002:a17:90b:4d81:b0:35d:a412:3c79 with SMTP id 98e67ed59e1d1-35dc7079cb6mr6805318a91.30.1775135280985; Thu, 02 Apr 2026 06:08:00 -0700 (PDT) Received: from fedora ([209.132.188.88]) by smtp.gmail.com with ESMTPSA id 98e67ed59e1d1-35dbe41b11fsm7822915a91.0.2026.04.02.06.07.48 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 02 Apr 2026 06:08:00 -0700 (PDT) Date: Thu, 2 Apr 2026 13:07:45 +0000 From: Hangbin Liu To: David Laight Cc: Richard Henderson , Matt Turner , Magnus Lindholm , Vineet Gupta , Brian Cain , "James E.J. Bottomley" , Helge Deller , Madhavan Srinivasan , Michael Ellerman , Nicholas Piggin , "Christophe Leroy (CS GROUP)" , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Yoshinori Sato , Rich Felker , John Paul Adrian Glaubitz , "David S. Miller" , Andreas Larsson , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , x86@kernel.org, "H. Peter Anvin" , Chris Zankel , Max Filippov , linux-alpha@vger.kernel.org, linux-kernel@vger.kernel.org, linux-snps-arc@lists.infradead.org, linux-hexagon@vger.kernel.org, linux-parisc@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-sh@vger.kernel.org, sparclinux@vger.kernel.org, Jakub Kicinski Subject: Re: [PATCH] cmpxchg: allow const-qualified old value in cmpxchg() Message-ID: References: <20260402-cmpxchg-v1-1-4561e2c05d2c@gmail.com> <20260402095747.6efbd456@pumpkin> Precedence: bulk X-Mailing-List: linux-hexagon@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260402095747.6efbd456@pumpkin> On Thu, Apr 02, 2026 at 09:57:47AM +0100, David Laight wrote: > > diff --git a/arch/alpha/include/asm/cmpxchg.h b/arch/alpha/include/asm/cmpxchg.h > > index ae1b96479d0c..b4b8dac759c4 100644 > > --- a/arch/alpha/include/asm/cmpxchg.h > > +++ b/arch/alpha/include/asm/cmpxchg.h > > @@ -234,7 +234,7 @@ ____cmpxchg(volatile void *ptr, unsigned long old, unsigned long new, > > > > #define arch_cmpxchg_local(ptr, o, n) \ > > ({ \ > > - __typeof__(*(ptr)) _o_ = (o); \ > > + __typeof__(*(ptr)) _o_ = (__typeof__(*(ptr)))(o); \ > > __typeof__(*(ptr)) _n_ = (n); \ > > (__typeof__(*(ptr))) ____cmpxchg((ptr), (unsigned long)_o_, \ > > (unsigned long)_n_, \ > > That looks like it loses the check that 'o' has the same type as '*ptr'. > Maybe this works? > auto _o_ = 1 ? (o) : *(ptr); > Oh, I didn't notice this. Thanks for the comment! Best Regards Hangbin