Messages in this thread | | | Subject | Re: [PATCH] arm64: Avoid pointless schedule_preempt_irq() invocations | From | Valentin Schneider <> | Date | Wed, 17 Jul 2019 10:54:09 +0100 |
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On 17/07/2019 09:43, Thomas Gleixner wrote: > When preempt_count is zero on return from interrupt then > schedule_preempt_irq() is invoked even if TIF_NEED_RESCHED is not set. > > That does not make sense because schedule_preempt_irq() has to go through a > full __schedule() for nothing in that case. > > Check TIF_NEED_RESCHED and invoke schedule_preempt_irq() only if set. > > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Don't we have NEED_RESCHED squashed into preempt count?
396244692232 ("arm64: preempt: Provide our own implementation of asm/preempt.h")
So the existing check should cover that, unless I'm missing something?
> --- > Found while staring at some RT wrecakge in that area. > --- > arch/arm64/kernel/entry.S | 4 ++++ > 1 file changed, 4 insertions(+) > > --- a/arch/arm64/kernel/entry.S > +++ b/arch/arm64/kernel/entry.S > @@ -680,6 +680,10 @@ alternative_if ARM64_HAS_IRQ_PRIO_MASKIN > orr x24, x24, x0 > alternative_else_nop_endif > cbnz x24, 1f // preempt count != 0 || NMI return path > + > + ldr x0, [tsk, #TSK_TI_FLAGS] // get flags > + tbz x0, #TIF_NEED_RESCHED, 1f // needs rescheduling? > + > bl preempt_schedule_irq // irq en/disable is done inside > 1: > #endif >
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