linux-kernel - Re: [PATCH v8 09/26] arm64: Unmask PMR before going idle

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Message-ID: <edc99513-3169-7238-f93b-d5ae9e1c8b4c@arm.com>
Date:   Fri, 18 Jan 2019 17:17:19 +0000
From:   Julien Thierry <julien.thierry@....com>
To:     Catalin Marinas <catalin.marinas@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, mark.rutland@....com,
        daniel.thompson@...aro.org, marc.zyngier@....com,
        will.deacon@....com, linux-kernel@...r.kernel.org,
        christoffer.dall@....com, james.morse@....com,
        joel@...lfernandes.org
Subject: Re: [PATCH v8 09/26] arm64: Unmask PMR before going idle



On 18/01/2019 16:23, Catalin Marinas wrote:
> On Tue, Jan 08, 2019 at 02:07:27PM +0000, Julien Thierry wrote:
>> CPU does not received signals for interrupts with a priority masked by
>> ICC_PMR_EL1. This means the CPU might not come back from a WFI
>> instruction.
>>
>> Make sure ICC_PMR_EL1 does not mask interrupts when doing a WFI.
>>
>> Since the logic of cpu_do_idle is becoming a bit more complex than just
>> two instructions, lets turn it from ASM to C.
> 
> I haven't checked all the call paths, so asking here: does the core code
> normally call arch_cpu_idle() with IRQs off?
> 

If you look at do_idle() in kernel/sched/idle.c, it does:

	while (!need_resched()) {
		[...]
		local_irq_disable();
		arch_cpu_idle_enter();

		[...]
		} else {
			cpuidle_idle_call();
		}
	}


Then cpuidle_idle_call() will call default_idle_call() (which calls
arch_cpu_idle()) either directly or via the cpuidle driver. My
understanding is that it always does the call with interrupts disabled.

Thanks,

-- 
Julien Thierry