Date: Sat, 10 May 2014 17:23:10 -0600 From: Ian Lepore <ian@FreeBSD.org> To: Hans Petter Selasky <hps@selasky.org> Cc: "freebsd-arm@freebsd.org" <freebsd-arm@FreeBSD.org>, Alexander Motin <mav@FreeBSD.org> Subject: Re: USB isochronous traffic with Rasberry Pi [WAS: Re: USB audio device on Raspberry Pi] Message-ID: <1399764190.22079.425.camel@revolution.hippie.lan> In-Reply-To: <536EA753.40905@selasky.org> References: <20140425154430.GA76168@utility-01.thismonkey.com> <5360C0A7.9010407@selasky.org> <1398867266.22079.51.camel@revolution.hippie.lan> <CAGW5k5bZ_bTQUXuzNm=tbwx3npz1_HoOR3vM8TBRVFs8zWCq-w@mail.gmail.com> <5362638B.1080104@selasky.org> <5363C133.2000304@selasky.org> <53677CB8.5000800@selasky.org> <CAJ-Vmo=XmH-RX6_i13NuAXhq-jTC%2BWedGiyOMJaPO4r014DSgw@mail.gmail.com> <1399303695.22079.239.camel@revolution.hippie.lan> <1399304157.22079.243.camel@revolution.hippie.lan> <CAJ-Vmok-%2B7%2Bcq%2BDa6_C2AA7BuP5readY_Gfwwm_RF5kh4VerQA@mail.gmail.com> <5368A93D.3070608@selasky.org> <5368AC03.8080401@selasky.org> <536CE5E9.8020408@selasky.org> <1399647986.22079.367.camel@revolution.hippie.lan> <536D0575.1040407@selasky.org> <1399661378.22079.376.camel@revolution.hippie.lan> <536DDA6D.7060101@selasky.org> <1399724697.22079.386.camel@revolution.hippie.l an> <536E2EBB.7030104@selasky.org> <1399742062.22079.403.camel@revolution.hippie.lan> <536EA597.3070700@selasky.org> <536EA753.40905@selasky.org>
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On Sun, 2014-05-11 at 00:25 +0200, Hans Petter Selasky wrote:
> Hi,
>
> This patch fixes the problem too:
>
> diff --git a/sys/arm/arm/machdep.c b/sys/arm/arm/machdep.c
> index 0490be7..8d53fab 100644
> --- a/sys/arm/arm/machdep.c
> +++ b/sys/arm/arm/machdep.c
> @@ -432,8 +432,12 @@ cpu_idle(int busy)
> cpu_idleclock();
> }
> #endif
> + register_t s;
> + s = intr_disable();
> if (!sched_runnable())
> cpu_sleep(0);
> + intr_restore(s);
> +
> #ifndef NO_EVENTTIMERS
> if (!busy) {
> cpu_activeclock();
>
> It appears some IRQ is happening when sched_runnable() is running, and
> then cpu_sleep(0) is executed even though sched_runnable() is no longer
> true.
>
> --HPS
Aha! Now I think you're on to something. Even after explaining why
interrupts should be disabled for WFI I didn't notice that we don't
disable interrupts before WFI. (I wonder if this is why I sometimes see
a lost timer interrupt and have to hit a key to un-wedge things.)
Can you try the attached? The spinlock_enter/exit calls are essentially
a combination of disabling interrupts and doing a critical_enter().
-- Ian
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Index: sys/arm/arm/machdep.c
===================================================================
--- sys/arm/arm/machdep.c (revision 265783)
+++ sys/arm/arm/machdep.c (working copy)
@@ -426,9 +426,9 @@ cpu_idle(int busy)
CTR2(KTR_SPARE2, "cpu_idle(%d) at %d",
busy, curcpu);
+ spinlock_enter();
#ifndef NO_EVENTTIMERS
if (!busy) {
- critical_enter();
cpu_idleclock();
}
#endif
@@ -437,9 +437,9 @@ cpu_idle(int busy)
#ifndef NO_EVENTTIMERS
if (!busy) {
cpu_activeclock();
- critical_exit();
}
#endif
+ spinlock_exit();
CTR2(KTR_SPARE2, "cpu_idle(%d) at %d done",
busy, curcpu);
}
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