linux-kernel - Re: [PATCH v2 05/10] um: Determine sleep based on need

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Message-Id: <20250912005428.2567361-1-tiwei.bie@linux.dev>
Date: Fri, 12 Sep 2025 08:54:28 +0800
From: Tiwei Bie <tiwei.bie@...ux.dev>
To: johannes@...solutions.net
Cc: richard@....at,
	anton.ivanov@...bridgegreys.com,
	benjamin@...solutions.net,
	arnd@...db.de,
	linux-um@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	tiwei.btw@...group.com,
	tiwei.bie@...ux.dev
Subject: Re: [PATCH v2 05/10] um: Determine sleep based on need_resched()

On Thu, 11 Sep 2025 11:27:04 +0200, Johannes Berg wrote:
> On Sun, 2025-08-10 at 13:51 +0800, Tiwei Bie wrote:
> > 
> >  void um_idle_sleep(void)
> >  {
> > -	if (time_travel_mode != TT_MODE_OFF)
> > +	if (time_travel_mode != TT_MODE_OFF) {
> >  		time_travel_sleep();
> > -	else
> > +	} else {
> > +		raw_local_irq_enable();
> >  		os_idle_sleep();
> > +		raw_local_irq_disable();
> > +	}
> 
> This seems wrong, with it, lockdep gets really unhappy, and if I remove
> this change it seems to work OK?
> 
> I'll note that arch_cpu_idle() for x86 also doesn't change anything with
> interrupts.

Thanks for catching that! I missed it. I'll take a closer look.

Regards,
Tiwei