linux-kernel - Re: [Xen-devel] [PATCH] xen: Add comment for missing FROZEN notifier transitions

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Date:	Mon, 4 Apr 2016 17:30:59 +0100
From:	David Vrabel <david.vrabel@...rix.com>
To:	Julien Grall <julien.grall@....com>,
	Anna-Maria Gleixner <anna-maria@...utronix.de>,
	<linux-kernel@...r.kernel.org>
CC:	<xen-devel@...ts.xenproject.org>, <sstabellini@...nel.org>,
	<rt@...utronix.de>, David Vrabel <david.vrabel@...rix.com>,
	Boris Ostrovsky <Boris.Ostrovsky@...cle.com>,
	Juergen Gross <JGross@...e.com>
Subject: Re: [Xen-devel] [PATCH] xen: Add comment for missing FROZEN notifier
 transitions

On 04/04/16 17:21, Julien Grall wrote:
> (CC Stefano new e-mail address)
> 
> Hello Anna-Maria,
> 
> On 04/04/2016 13:32, Anna-Maria Gleixner wrote:
>> Xen guests do not offline/online CPUs during suspend/resume and
>> therefore FROZEN notifier transitions are not required. Add this
>> explanation as a comment in the code to get not confused why
>> CPU_TASKS_FROZEN masked transitions are not considered.

Alternatively, these could be added even if they are not encountered.
This might be more future-proof but the documentation might be clearer.

Boris, Juergen, any opinion?

David>> --- a/drivers/xen/events/events_fifo.c
>> +++ b/drivers/xen/events/events_fifo.c
>> @@ -425,6 +425,12 @@ static int evtchn_fifo_cpu_notification(
>>       int cpu = (long)hcpu;
>>       int ret = 0;
>>
>> +    /*
>> +     * Xen guests do not offline/online CPUs during
>> +     * suspend/resume, thus CPU_TASKS_FROZEN masked transitions
>> +     * are not considered.
>> +    */
> 
> NIT: The '*' is not aligned with the others.

If this doesn't need any other changes, I'll fix this on commit.

David