linux-kernel - Re: [PATCH RESEND 1/2] x86/locking: Use ALT_OUTPUT_SP() for percpu_{,try_}cmpxchg{64,128}

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Message-ID: <38c424bd-8f49-466a-b414-93a45a7ee3ec@intel.com>
Date: Thu, 13 Feb 2025 14:54:44 -0800
From: Dave Hansen <dave.hansen@...el.com>
To: Uros Bizjak <ubizjak@...il.com>
Cc: x86@...nel.org, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
 Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...nel.org>,
 Borislav Petkov <bp@...en8.de>, Dave Hansen <dave.hansen@...ux.intel.com>,
 "H. Peter Anvin" <hpa@...or.com>, Dennis Zhou <dennis@...nel.org>,
 Tejun Heo <tj@...nel.org>, Christoph Lameter <cl@...ux.com>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: Re: [PATCH RESEND 1/2] x86/locking: Use ALT_OUTPUT_SP() for
 percpu_{,try_}cmpxchg{64,128}_op()

On 2/13/25 13:17, Uros Bizjak wrote:
>> Basically, you've told me what the patch does, but not why anyone should
>> care or why it should be applied.
> This is actually explained at length in the comment for
> ASM_CALL_CONSTRAINT, which ALT_OUTPUT_SP macro uses.

Great info, thanks! Could you give the patch another shot and include
this in the changelog, please? Better yet, you could paraphrase the
comment so that we don't have to go searching for it.