linux-kernel - Re: [PATCH] mm: hugetlb: avoid soft lockup when mprotect with PROT

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Message-ID: <1038c7c7-81d6-f273-6fa1-93eb7206d5ed@gentwo.org>
Date: Fri, 26 Sep 2025 09:29:54 -0700 (PDT)
From: "Christoph Lameter (Ampere)" <cl@...two.org>
To: Yang Shi <yang@...amperecomputing.com>
cc: muchun.song@...ux.dev, osalvador@...e.de, david@...hat.com, 
    akpm@...ux-foundation.org, catalin.marinas@....com, will@...nel.org, 
    carl@...amperecomputing.com, linux-mm@...ck.org, 
    linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: hugetlb: avoid soft lockup when mprotect with
 PROT_MTE

On Fri, 26 Sep 2025, Yang Shi wrote:

> When calling mprotect() with PROT_MTE, kernel will initialize MTE tags
> for every single page in the affected area. Soft lockup was observed
> when doing this for large HugeTLB memory area in our customer's workload
> (~300GB memory):

AFAICT this is a bug fix. The hugetlb path should be doing a
cond_resched() like the base page code does.

It is not MTE specific. If other processing takes a long time in the loop
(setting up terabyte size mappings for hugetlb for example) then the
softlockup could also be triggered on non MTE workloads.

Reviewed-by: Christoph Lameter (Ampere) <cl@...two.org>