linux-kernel - Re: [patch v3 3/7] x86/smp: Remove pointless wmb()s from native_stop_other

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Date:   Tue, 20 Jun 2023 10:47:44 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     LKML <linux-kernel@...r.kernel.org>, x86@...nel.org,
        Mario Limonciello <mario.limonciello@....com>,
        Tom Lendacky <thomas.lendacky@....com>,
        Tony Battersby <tonyb@...ernetics.com>,
        Ashok Raj <ashok.raj@...ux.intel.com>,
        Tony Luck <tony.luck@...el.com>,
        Arjan van de Veen <arjan@...ux.intel.com>,
        Eric Biederman <ebiederm@...ssion.com>
Subject: Re: [patch v3 3/7] x86/smp: Remove pointless wmb()s from
 native_stop_other_cpus()

On Thu, Jun 15, 2023 at 10:33:54PM +0200, Thomas Gleixner wrote:
> The wmb()s before sending the IPIs are not synchronizing anything.
> 
> If at all then the apic IPI functions have to provide or act as appropriate
> barriers.
> 
> Remove these cargo cult barriers which have no explanation of what they are
> synchronizing.
> 
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> ---
> V3: Remove second instance and reword changelog - PeterZ
> ---
>  arch/x86/kernel/smp.c |    6 ------
>  1 file changed, 6 deletions(-)

Reviewed-by: Borislav Petkov (AMD) <bp@...en8.de>

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette