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

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Message-ID: <78c8e39d9719a26c6e492e895b070794eb8218ea.camel@sipsolutions.net>
Date: Thu, 11 Sep 2025 11:27:04 +0200
From: Johannes Berg <johannes@...solutions.net>
To: Tiwei Bie <tiwei.bie@...ux.dev>, richard@....at, 
	anton.ivanov@...bridgegreys.com
Cc: linux-um@...ts.infradead.org, linux-kernel@...r.kernel.org, 
	benjamin@...solutions.net, arnd@...db.de, tiwei.btw@...group.com
Subject: Re: [PATCH v2 05/10] um: Determine sleep based on need_resched()

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.

Was there something else that required this change that I'm missing?

johannes