linux-kernel - Re: Question on migrate

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Message-ID: <YA/faHXHWw1UfmUB@hirez.programming.kicks-ass.net>
Date:   Tue, 26 Jan 2021 10:22:48 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     "Zhang, Qiang" <Qiang.Zhang@...driver.com>
Cc:     "tglx@...utronix.de" <tglx@...utronix.de>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Question on migrate_disabe/enable()

On Tue, Jan 26, 2021 at 02:12:45AM +0000, Zhang, Qiang wrote:
> Hello Peterz, tglx
> 
> I have some questions about migrate_disabe/enable(),  in the past
> migrate_disabe/enable() is replaced by preempt_disable/enable() in no
> RT system.
> 
> And now migrate_disabe/enable() has its own implementation, I want to
> know in migrate_disabe/enable() critical area is blocking allowed?  

Yes, obviously. Otherwise it would've been preempt_disable().

> If allowed, There's a blockage in migrate_disabe/enable() critical
> area, and this time if CPU going offline，offline time will be longer.
> Is this normal phenomenon？

Ofcourse.