Messages in this thread | | | Date | Mon, 24 Apr 2023 19:23:10 +0800 | Subject | Re: Loongson (and other $ARCHs?) idle VS timer enqueue | From | maobibo <> |
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在 2023/4/24 16:26, Frederic Weisbecker 写道: > On Sun, Apr 23, 2023 at 09:52:49PM +0800, bibo, mao wrote: >> >> >> 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. > > Nop, TIF_NEED_RESCHED is set only if a task is ready to run after the interrupt, > not if the interrupt only modified/added a timer. Got it, thanks for your explanation, it is actually one issue in the LoongArch ASM code __arch_cpu_idle().
Regards Bibo, Mao
> >>> @@ -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? > > Indeed we can remove the check to TIF_RESCHED! > > Thanks!
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