preempt_disable and sleep()

preempt_disable and sleep()

[ratheesh k]

I am running RT linux .

/* code snippet */

preempt_disable()
...........
sleep(10);
'............
preempt_enable()


will this sleep() will cause reschedule ?.

if an interrupt comes  while premption is disabled , how it is handled ?.

Thanks,
Ratheesh

Re: preempt_disable and sleep()

[Sven-Thorsten Dietrich]

On Fri, 2010-05-14 at 00:02 +0530, ratheesh k wrote:
> I am running RT linux .
> 
> /* code snippet */
> 
> preempt_disable()
> ...........
> sleep(10);
> '............
> preempt_enable()
> 
> 
> will this sleep() will cause reschedule ?.
> 

Why would you do this?

If you had tried this code, you would have seen the corresponding stack
dump on the console.

> if an interrupt comes  while premption is disabled , how it is handled ?.
> 

Depends on the number of (idle) cores, the setting of CONFIG_PREEMPT_[]
and the type of interrupt.

RT threaded IRQs would not run until preemption is enabled on a single
core system.



> Thanks,
> Ratheesh
> --
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Re: preempt_disable and sleep()

[ratheesh k]

On Fri, May 14, 2010 at 12:13 AM, Sven-Thorsten Dietrich
<thebigcorporation@gmail.com> wrote:

> Why would you do this?
I was reading some linux kernel journel about preempt_disable() . This
a doubt came to me .


> If you had tried this code, you would have seen the corresponding stack
> dump on the console.


Why it so .? could you explain a little more ? .sleep() will schedule
() , which inturn give back control to kernel .

Thank,
Ratheesh

On Fri, May 14, 2010 at 12:13 AM, Sven-Thorsten Dietrich
<thebigcorporation@gmail.com> wrote:
> On Fri, 2010-05-14 at 00:02 +0530, ratheesh k wrote:
>> I am running RT linux .
>>
>> /* code snippet */
>>
>> preempt_disable()
>> ...........
>> sleep(10);
>> '............
>> preempt_enable()
>>
>>
>> will this sleep() will cause reschedule ?.
>>
>
> Why would you do this?
>
> If you had tried this code, you would have seen the corresponding stack
> dump on the console.
>
>> if an interrupt comes  while premption is disabled , how it is handled ?.
>>
>
> Depends on the number of (idle) cores, the setting of CONFIG_PREEMPT_[]
> and the type of interrupt.
>
> RT threaded IRQs would not run until preemption is enabled on a single
> core system.
>
>
>
>> Thanks,
>> Ratheesh
>> --
>> To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in
>> the body of a message to majordomo@vger.kernel.org
>> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>
>
>
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Re: preempt_disable and sleep()

[Paul E. McKenney]

On Fri, May 14, 2010 at 08:16:07AM +0530, ratheesh k wrote:
> On Fri, May 14, 2010 at 12:13 AM, Sven-Thorsten Dietrich
> <thebigcorporation@gmail.com> wrote:
> 
> > Why would you do this?
> I was reading some linux kernel journel about preempt_disable() . This
> a doubt came to me .
> 
> 
> > If you had tried this code, you would have seen the corresponding stack
> > dump on the console.
> 
> 
> Why it so .? could you explain a little more ? .sleep() will schedule
> () , which inturn give back control to kernel .

Sleeping in the kernel with preemption disabled is considered to be a
bug.  So the scheduler will print an error and a stack dump when this
happens.

In contrast, it is OK to do the following:

	preempt_disable();
	do_something();
	preempt_enable();
	schedule();
	preempt_disable();
	do_something_else();
	preempt_enable();

							Thanx, Paul

> Thank,
> Ratheesh
> 
> On Fri, May 14, 2010 at 12:13 AM, Sven-Thorsten Dietrich
> <thebigcorporation@gmail.com> wrote:
> > On Fri, 2010-05-14 at 00:02 +0530, ratheesh k wrote:
> >> I am running RT linux .
> >>
> >> /* code snippet */
> >>
> >> preempt_disable()
> >> ...........
> >> sleep(10);
> >> '............
> >> preempt_enable()
> >>
> >>
> >> will this sleep() will cause reschedule ?.
> >>
> >
> > Why would you do this?
> >
> > If you had tried this code, you would have seen the corresponding stack
> > dump on the console.
> >
> >> if an interrupt comes  while premption is disabled , how it is handled ?.
> >>
> >
> > Depends on the number of (idle) cores, the setting of CONFIG_PREEMPT_[]
> > and the type of interrupt.
> >
> > RT threaded IRQs would not run until preemption is enabled on a single
> > core system.
> >
> >
> >
> >> Thanks,
> >> Ratheesh
> >> --
> >> To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in
> >> the body of a message to majordomo@vger.kernel.org
> >> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> >
> >
> >
> --
> To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in
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