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From: Juergen Gross <jgross@suse.com>
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
	David Vrabel <david.vrabel@citrix.com>,
	Julien Grall <julien.grall@arm.com>,
	Anna-Maria Gleixner <anna-maria@linutronix.de>,
	linux-kernel@vger.kernel.org
Cc: xen-devel@lists.xenproject.org, sstabellini@kernel.org, rt@linutronix.de
Subject: Re: [PATCH] xen: Add comment for missing FROZEN notifier transitions
Date: Tue, 5 Apr 2016 06:22:16 +0200	[thread overview]
Message-ID: <57033D78.8010306__1561.26646693355$1459830223$gmane$org@suse.com> (raw)
In-Reply-To: <57029AC7.90201@oracle.com>

On 04/04/16 18:48, Boris Ostrovsky wrote:
> On 04/04/2016 12:30 PM, David Vrabel wrote:
>> 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?

I'd rather do more than a comment:

Either mask CPU_TASKS_FROZEN from action if it really doesn't matter
whether the flag is set or not (which IMHO is the case here), or
BUG_ON(action & CPU_TASKS_FROZEN) if this really should never happen.

> Wouldn't the same comment need to be added to xen_hvm_cpu_notify()?

The patch of Anna-Maria does that.


Juergen

> 
> 
> -boris
> 
> 
>>
>> 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
> 
> 


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  parent reply	other threads:[~2016-04-05  4:22 UTC|newest]

Thread overview: 9+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1459773140-43707-1-git-send-email-anna-maria@linutronix.de>
2016-04-04 16:21 ` Julien Grall
     [not found] ` <57029499.7070007@arm.com>
2016-04-04 16:30   ` David Vrabel
     [not found]   ` <570296C3.70805@citrix.com>
2016-04-04 16:48     ` Boris Ostrovsky
     [not found]     ` <57029AC7.90201@oracle.com>
2016-04-05  4:22       ` Juergen Gross [this message]
     [not found]       ` <57033D78.8010306@suse.com>
2016-04-06 23:52         ` Stefano Stabellini
2016-04-06 13:09 ` David Vrabel
     [not found] ` <57050A98.80901@cantab.net>
2016-04-06 14:08   ` [PREEMPT-RT] " Anna-Maria Gleixner
2016-04-06 23:53   ` Stefano Stabellini
2016-04-04 12:32 Anna-Maria Gleixner

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