linux-kernel - Re: [PATCH] MIPS: SMP: Move the AP sync point before the non-parallel aware functions

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Message-ID: <aCwmPKm3NjbhLiNA@alpha.franken.de>
Date: Tue, 20 May 2025 08:50:36 +0200
From: Thomas Bogendoerfer <tsbogend@...ha.franken.de>
To: Gregory CLEMENT <gregory.clement@...tlin.com>
Cc: Huacai Chen <chenhuacai@...nel.org>,
	Jiaxun Yang <jiaxun.yang@...goat.com>,
	Vladimir Kondratiev <vladimir.kondratiev@...ileye.com>,
	Théo Lebrun <theo.lebrun@...tlin.com>,
	Tawfik Bayouk <tawfik.bayouk@...ileye.com>,
	Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
	linux-mips@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] MIPS: SMP: Move the AP sync point before the
 non-parallel aware functions

On Mon, May 05, 2025 at 02:57:58PM +0200, Gregory CLEMENT wrote:
> When CONFIG_HOTPLUG_PARALLEL is enabled, the code executing before
> cpuhp_ap_sync_alive() is executed in parallel, while after it is
> serialized. The functions set_cpu_sibling_map() and set_cpu_core_map()
> were not designed to be executed in parallel, so by moving the
> cpuhp_ap_sync_alive() before cpuhp_ap_sync_alive(), we then ensure
> they will be called serialized.
> 
> The measurement done on EyeQ5 did not show any relevant boot time
> increase after applying this patch.
> 
> Reported-by: Huacai Chen <chenhuacai@...nel.org>
> Signed-off-by: Gregory CLEMENT <gregory.clement@...tlin.com>
> ---
> Hello,
> 
> As discussed last week [1], this is the patch that fixes the potential
> issue with the functions set_cpu_sibling_map() and set_cpu_core_map().
> 
> Gregory

applied to mips-next with a Fixes tag added

Thomas.

-- 
Crap can work. Given enough thrust pigs will fly, but it's not necessarily a
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