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Re: [patch] sched,rt: __always_inline preemptible_lazy()

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  Re: [patch]  sched,rt: __always_inline preemptible_lazy() "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2016-02-22 04:40 +0100
    Re: [patch]  sched,rt: __always_inline preemptible_lazy() Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-02-22 05:10 +0100
      Re: [patch]  sched,rt: __always_inline preemptible_lazy() "Hillf Danton" <hillf.zj@alibaba-inc.com> - 2016-02-22 06:40 +0100

#1339116 — Re: [patch] sched,rt: __always_inline preemptible_lazy()

> 
> homer: # nm kernel/sched/core.o|grep preemptible_lazy
> 00000000000000b5 t preemptible_lazy
> 
> echo wakeup_rt > current_tracer ==> Welcome to infinity.
> 
> Signed-off-bx: Mike Galbraith <umgwanakikbuti@gmail.com>
> ---

Fat finger?

BTW, would you please make a better description of the
problem this patch is trying to address/fix?

Hillf
>  kernel/sched/core.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3469,7 +3469,7 @@ static void __sched notrace preempt_sche
>   * set by a RT task. Oterwise we try to avoid beeing scheduled out as long as
>   * preempt_lazy_count counter >0.
>   */
> -static int preemptible_lazy(void)
> +static __always_inline int preemptible_lazy(void)
>  {
>  	if (test_thread_flag(TIF_NEED_RESCHED))
>  		return 1;

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#1339121

On Mon, 2016-02-22 at 11:36 +0800, Hillf Danton wrote:
> > 
> > homer: # nm kernel/sched/core.o|grep preemptible_lazy
> > 00000000000000b5 t preemptible_lazy
> > 
> > echo wakeup_rt > current_tracer ==> Welcome to infinity.
> > 
> > Signed-off-bx: Mike Galbraith <umgwanakikbuti@gmail.com>
> > ---
> 
> Fat finger?

Yeah, my fingers don't take direction all that well.

> BTW, would you please make a better description of the
> problem this patch is trying to address/fix?

Ok, I thought it was clear what happens.

sched,rt: __always_inline preemptible_lazy()

Functions called within a notrace function must either also be
notrace or be inlined, lest recursion blow the stack.

homer: # nm kernel/sched/core.o|grep preemptible_lazy
00000000000000b5 t preemptible_lazy

echo wakeup_rt > current_tracer ==> Welcome to infinity.

Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
---
 kernel/sched/core.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -3469,7 +3469,7 @@ static void __sched notrace preempt_sche
  * set by a RT task. Oterwise we try to avoid beeing scheduled out as long as
  * preempt_lazy_count counter >0.
  */
-static int preemptible_lazy(void)
+static __always_inline int preemptible_lazy(void)
 {
 	if (test_thread_flag(TIF_NEED_RESCHED))
 		return 1;

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#1339140

> 
> sched,rt: __always_inline preemptible_lazy()
> 
> Functions called within a notrace function must either also be
> notrace or be inlined, lest recursion blow the stack.
> 
> homer: # nm kernel/sched/core.o|grep preemptible_lazy
> 00000000000000b5 t preemptible_lazy
> 
> echo wakeup_rt > current_tracer ==> Welcome to infinity.
> 
> Signed-off-by: Mike Galbraith <umgwanakikbuti@gmail.com>
> ---

Thank you, Mike.

Acked-by: Hillf Danton <hillf.zj@alibaba-inc.com>

>  kernel/sched/core.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3469,7 +3469,7 @@ static void __sched notrace preempt_sche
>   * set by a RT task. Oterwise we try to avoid beeing scheduled out as long as
>   * preempt_lazy_count counter >0.
>   */
> -static int preemptible_lazy(void)
> +static __always_inline int preemptible_lazy(void)
>  {
>  	if (test_thread_flag(TIF_NEED_RESCHED))
>  		return 1;

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