Messages in this thread | | | Date | Sun, 23 Apr 2023 21:52:49 +0800 | Subject | Re: Loongson (and other $ARCHs?) idle VS timer enqueue | From | "bibo, mao" <> |
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在 2023/4/22 23:04, Peter Zijlstra 写道: > On Sat, Apr 22, 2023 at 04:21:45PM +0200, Frederic Weisbecker wrote: >> On Sat, Apr 22, 2023 at 10:17:00AM +0200, Peter Zijlstra wrote: >>> diff --git a/arch/loongarch/kernel/genex.S b/arch/loongarch/kernel/genex.S >>> index 44ff1ff64260..5a102ff80de0 100644 >>> --- a/arch/loongarch/kernel/genex.S >>> +++ b/arch/loongarch/kernel/genex.S >>> @@ -40,6 +40,7 @@ SYM_FUNC_START(handle_vint) >>> ori t0, t0, 0x1f >>> xori t0, t0, 0x1f >>> bne t0, t1, 1f >>> + addi.d t0, t0, 0x20 >>> LONG_S t0, sp, PT_ERA >>> 1: move a0, sp >>> move a1, sp >> >> But the interrupts are enabled in C from arch_cpu_idle(), which >> only then calls the ASM __arch_cpu_idle(). So if the interrupt happens >> somewhere in between the call, the rollback (or fast-forward now) >> doesn't apply. I do not know much details about scheduler and timer, if the interrupt happens between the call, will flag _TIF_NEED_RESCHED be set? If it is set, the rollback will still apply.
>> >> I guess interrupts need to be re-enabled from ASM in the beginning >> of __arch_cpu_idle() so that it's part of the fast-forward region. > > Right; something like so I suppose, but at this point I'm really just > guessing... Loongarch person will have to do. > > diff --git a/arch/loongarch/kernel/genex.S b/arch/loongarch/kernel/genex.S > index 44ff1ff64260..4814ac5334ef 100644 > --- a/arch/loongarch/kernel/genex.S > +++ b/arch/loongarch/kernel/genex.S > @@ -19,13 +19,13 @@ > .align 5 > SYM_FUNC_START(__arch_cpu_idle) > /* start of rollback region */ > + move t0, CSR_CRMD_IE > + csrxchg t0, t0, LOONGARCH_CSR_CRMD > LONG_L t0, tp, TI_FLAGS > nop > andi t0, t0, _TIF_NEED_RESCHED > bnez t0, 1f > nop > - nop > - nop > idle 0 > /* end of rollback region */ > 1: jr ra > @@ -40,6 +40,7 @@ SYM_FUNC_START(handle_vint) > ori t0, t0, 0x1f > xori t0, t0, 0x1f > bne t0, t1, 1f > + addi.d t0, t0, 0x20 It is more reasonable with this patch, this will jump out of idle function directly after interrupt returns. If so, can we remove checking _TIF_NEED_RESCHED in idle ASM function?
> + move t0, CSR_CRMD_IE > + csrxchg t0, t0, LOONGARCH_CSR_CRMD - LONG_L t0, tp, TI_FLAGS + nop > nop - andi t0, t0, _TIF_NEED_RESCHED - bnez t0, 1f + nop + nop > nop > - nop > - nop > idle 0
Regards Bibo, Mao > LONG_S t0, sp, PT_ERA > 1: move a0, sp > move a1, sp > diff --git a/arch/loongarch/kernel/idle.c b/arch/loongarch/kernel/idle.c > index 0b5dd2faeb90..5ba72d229920 100644 > --- a/arch/loongarch/kernel/idle.c > +++ b/arch/loongarch/kernel/idle.c > @@ -11,7 +11,6 @@ > > void __cpuidle arch_cpu_idle(void) > { > - raw_local_irq_enable(); > __arch_cpu_idle(); /* idle instruction needs irq enabled */ > raw_local_irq_disable(); > }
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