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* Re: [PATCH] xen: Add comment for missing FROZEN notifier transitions
       [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>
                   ` (2 subsequent siblings)
  3 siblings, 0 replies; 8+ messages in thread
From: Julien Grall @ 2016-04-04 16:21 UTC (permalink / raw)
  To: Anna-Maria Gleixner, linux-kernel
  Cc: xen-devel, sstabellini, rt, David Vrabel

(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.
>
> Cc: David Vrabel <david.vrabel@citrix.com>
> Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> Cc: xen-devel@lists.xenproject.org
> Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
> ---
>   arch/arm/xen/enlighten.c         |    6 ++++++
>   arch/x86/xen/enlighten.c         |    7 +++++++
>   drivers/xen/events/events_fifo.c |    6 ++++++
>   3 files changed, 19 insertions(+)
>
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -213,6 +213,12 @@ static int xen_cpu_notification(struct n
>   				unsigned long action,
>   				void *hcpu)
>   {
> +	/*
> +	 * Xen guests do not offline/online CPUs during
> +	 * suspend/resume, thus CPU_TASKS_FROZEN masked transitions
> +	 * are not considered.
> +	 */
> +
>   	switch (action) {
>   	case CPU_STARTING:
>   		xen_percpu_init();
> --- a/arch/x86/xen/enlighten.c
> +++ b/arch/x86/xen/enlighten.c
> @@ -1788,6 +1788,13 @@ static int xen_hvm_cpu_notify(struct not
>   			      void *hcpu)
>   {
>   	int cpu = (long)hcpu;
> +
> +	/*
> +	 * Xen guests do not offline/online CPUs during
> +	 * suspend/resume, thus CPU_TASKS_FROZEN masked transitions
> +	 * are not considered.
> +	 */
> +
>   	switch (action) {
>   	case CPU_UP_PREPARE:
>   		xen_vcpu_setup(cpu);
> --- 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.

> +
>   	switch (action) {
>   	case CPU_UP_PREPARE:
>   		if (!per_cpu(cpu_control_block, cpu))
>

Regards,

-- 
Julien Grall

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http://lists.xen.org/xen-devel

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH] xen: Add comment for missing FROZEN notifier transitions
       [not found] ` <57029499.7070007@arm.com>
@ 2016-04-04 16:30   ` David Vrabel
       [not found]   ` <570296C3.70805@citrix.com>
  1 sibling, 0 replies; 8+ messages in thread
From: David Vrabel @ 2016-04-04 16:30 UTC (permalink / raw)
  To: Julien Grall, Anna-Maria Gleixner, linux-kernel
  Cc: Juergen Gross, sstabellini, rt, xen-devel, Boris Ostrovsky, David Vrabel

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

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^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH] xen: Add comment for missing FROZEN notifier transitions
       [not found]   ` <570296C3.70805@citrix.com>
@ 2016-04-04 16:48     ` Boris Ostrovsky
       [not found]     ` <57029AC7.90201@oracle.com>
  1 sibling, 0 replies; 8+ messages in thread
From: Boris Ostrovsky @ 2016-04-04 16:48 UTC (permalink / raw)
  To: David Vrabel, Julien Grall, Anna-Maria Gleixner, linux-kernel
  Cc: Juergen Gross, xen-devel, sstabellini, rt

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?

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


-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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http://lists.xen.org/xen-devel

^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH] xen: Add comment for missing FROZEN notifier transitions
       [not found]     ` <57029AC7.90201@oracle.com>
@ 2016-04-05  4:22       ` Juergen Gross
       [not found]       ` <57033D78.8010306@suse.com>
  1 sibling, 0 replies; 8+ messages in thread
From: Juergen Gross @ 2016-04-05  4:22 UTC (permalink / raw)
  To: Boris Ostrovsky, David Vrabel, Julien Grall, Anna-Maria Gleixner,
	linux-kernel
  Cc: xen-devel, sstabellini, rt

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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^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH] xen: Add comment for missing FROZEN notifier transitions
       [not found] <1459773140-43707-1-git-send-email-anna-maria@linutronix.de>
  2016-04-04 16:21 ` [PATCH] xen: Add comment for missing FROZEN notifier transitions Julien Grall
       [not found] ` <57029499.7070007@arm.com>
@ 2016-04-06 13:09 ` David Vrabel
       [not found] ` <57050A98.80901@cantab.net>
  3 siblings, 0 replies; 8+ messages in thread
From: David Vrabel @ 2016-04-06 13:09 UTC (permalink / raw)
  To: Anna-Maria Gleixner, linux-kernel
  Cc: xen-devel, David Vrabel, rt, Stefano Stabellini

On 04/04/16 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.
> 
> Cc: David Vrabel <david.vrabel@citrix.com>
> Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> Cc: xen-devel@lists.xenproject.org 
> Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
> ---
>  arch/arm/xen/enlighten.c         |    6 ++++++
>  arch/x86/xen/enlighten.c         |    7 +++++++
>  drivers/xen/events/events_fifo.c |    6 ++++++
>  3 files changed, 19 insertions(+)
> 
> --- a/arch/arm/xen/enlighten.c
> +++ b/arch/arm/xen/enlighten.c
> @@ -213,6 +213,12 @@ static int xen_cpu_notification(struct n
>  				unsigned long action,
>  				void *hcpu)
>  {
> +	/*
> +	 * Xen guests do not offline/online CPUs during
> +	 * suspend/resume, thus CPU_TASKS_FROZEN masked transitions
> +	 * are not considered.
> +	 */

This may not be true for arm guests.

David

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^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PREEMPT-RT] [PATCH] xen: Add comment for missing FROZEN notifier transitions
       [not found] ` <57050A98.80901@cantab.net>
@ 2016-04-06 14:08   ` Anna-Maria Gleixner
  2016-04-06 23:53   ` Stefano Stabellini
  1 sibling, 0 replies; 8+ messages in thread
From: Anna-Maria Gleixner @ 2016-04-06 14:08 UTC (permalink / raw)
  To: David Vrabel
  Cc: xen-devel, rt, linux-kernel, Stefano Stabellini, David Vrabel

On Wed, 6 Apr 2016, David Vrabel wrote:

> On 04/04/16 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.
> > 
> > Cc: David Vrabel <david.vrabel@citrix.com>
> > Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> > Cc: xen-devel@lists.xenproject.org 
> > Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
> > ---
> >  arch/arm/xen/enlighten.c         |    6 ++++++
> >  arch/x86/xen/enlighten.c         |    7 +++++++
> >  drivers/xen/events/events_fifo.c |    6 ++++++
> >  3 files changed, 19 insertions(+)
> > 
> > --- a/arch/arm/xen/enlighten.c
> > +++ b/arch/arm/xen/enlighten.c
> > @@ -213,6 +213,12 @@ static int xen_cpu_notification(struct n
> >  				unsigned long action,
> >  				void *hcpu)
> >  {
> > +	/*
> > +	 * Xen guests do not offline/online CPUs during
> > +	 * suspend/resume, thus CPU_TASKS_FROZEN masked transitions
> > +	 * are not considered.
> > +	 */
> 
> This may not be true for arm guests.

Ok. Should the frozen transitions be handled the same way than the
corresponding non frozen transitions? If yes and if it doesn't matter
to mask action with ~CPU_TASKS_FROZEN in arch/x86/xen/enlighten.c and
drivers/xen/events/events_fifo.c like Juergen sugessts, I could change
the patch by masking action.

Anna-Maria

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^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH] xen: Add comment for missing FROZEN notifier transitions
       [not found]       ` <57033D78.8010306@suse.com>
@ 2016-04-06 23:52         ` Stefano Stabellini
  0 siblings, 0 replies; 8+ messages in thread
From: Stefano Stabellini @ 2016-04-06 23:52 UTC (permalink / raw)
  To: Juergen Gross
  Cc: sstabellini, linux-kernel, Julien Grall, David Vrabel, xen-devel,
	Boris Ostrovsky, Anna-Maria Gleixner, rt

On Tue, 5 Apr 2016, Juergen Gross wrote:
> 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.

I agree

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^ permalink raw reply	[flat|nested] 8+ messages in thread

* Re: [PATCH] xen: Add comment for missing FROZEN notifier transitions
       [not found] ` <57050A98.80901@cantab.net>
  2016-04-06 14:08   ` [PREEMPT-RT] " Anna-Maria Gleixner
@ 2016-04-06 23:53   ` Stefano Stabellini
  1 sibling, 0 replies; 8+ messages in thread
From: Stefano Stabellini @ 2016-04-06 23:53 UTC (permalink / raw)
  To: David Vrabel
  Cc: Stefano Stabellini, linux-kernel, David Vrabel, xen-devel,
	Anna-Maria Gleixner, rt

On Wed, 6 Apr 2016, David Vrabel wrote:
> On 04/04/16 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.
> > 
> > Cc: David Vrabel <david.vrabel@citrix.com>
> > Cc: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
> > Cc: xen-devel@lists.xenproject.org 
> > Signed-off-by: Anna-Maria Gleixner <anna-maria@linutronix.de>
> > ---
> >  arch/arm/xen/enlighten.c         |    6 ++++++
> >  arch/x86/xen/enlighten.c         |    7 +++++++
> >  drivers/xen/events/events_fifo.c |    6 ++++++
> >  3 files changed, 19 insertions(+)
> > 
> > --- a/arch/arm/xen/enlighten.c
> > +++ b/arch/arm/xen/enlighten.c
> > @@ -213,6 +213,12 @@ static int xen_cpu_notification(struct n
> >  				unsigned long action,
> >  				void *hcpu)
> >  {
> > +	/*
> > +	 * Xen guests do not offline/online CPUs during
> > +	 * suspend/resume, thus CPU_TASKS_FROZEN masked transitions
> > +	 * are not considered.
> > +	 */
> 
> This may not be true for arm guests.
 
ARM guests behave like x86 PV guests in this regard. I expect the
comment to be appropriate for both archs or none.

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^ permalink raw reply	[flat|nested] 8+ messages in thread

end of thread, other threads:[~2016-04-06 23:53 UTC | newest]

Thread overview: 8+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
     [not found] <1459773140-43707-1-git-send-email-anna-maria@linutronix.de>
2016-04-04 16:21 ` [PATCH] xen: Add comment for missing FROZEN notifier transitions 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
     [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

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