linux-kernel - Re: [PATCH 05/11] smp: Enable preemption early in smp_call_function_many

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Message-ID: <20260206094700.GR1282955@noisy.programming.kicks-ass.net>
Date: Fri, 6 Feb 2026 10:47:00 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Chuyi Zhou <zhouchuyi@...edance.com>
Cc: tglx@...utronix.de, mingo@...hat.com, luto@...nel.org,
	paulmck@...nel.org, muchun.song@...ux.dev, bp@...en8.de,
	dave.hansen@...ux.intel.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 05/11] smp: Enable preemption early in
 smp_call_function_many_cond

On Fri, Feb 06, 2026 at 04:43:48PM +0800, Chuyi Zhou wrote:

> However, 99% of callers have preemption disabled, some of them even 
> invoking it within spin_locks (for example, we might trigger a TLB flush 
> while holding pte spinlocks).

Then 99% of the callers don't benefit from this and won't see your
latency reduction -- and will be broken on PREEMPT_RT, no?