> Date: Sun, 24 Jul 2022 19:33:57 -0500
> From: Scott Cheloha <scottchel...@gmail.com>
>
> On Sat, Jul 23, 2022 at 08:14:32PM -0500, Scott Cheloha wrote:
> >
> > [...]
> >
> > I don't have a powerpc64 machine, so this is untested. [...]
>
> gkoehler@ has pointed out two dumb typos in the prior patch. My bad.
>
> Here is a corrected patch that, according to gkoehler@, actually
> compiles.
Thanks. I already figured that bit out myself. Did some limited
testing, but it seems to work correctly. No noticable effect on the
timekeeping even when building clang on all the (4) cores.
Regarding the diff, I think it would be better to avoid changing
trap.c. That function is complicated enough and splitting the logic
for this over three files makes it a bit harder to understand. So you
could have:
void
decr_intr(struct trapframe *frame)
{
struct cpu_info *ci = curcpu();
...
int s;
if (ci->ci_cpl >= IPL_CLOCK) {
ci->ci_dec_deferred = 1;
mtdec(UINT32_MAX >> 1); /* clear DEC exception */
return;
}
ci->ci_dec_deferred = 0;
...
}
That has the downside of course that it will be slightly less
efficient if we're at IPL_CLOCK or above, but that really shouldn't
happen often enough for it to matter.
> Index: include/cpu.h
> ===================================================================
> RCS file: /cvs/src/sys/arch/powerpc64/include/cpu.h,v
> retrieving revision 1.31
> diff -u -p -r1.31 cpu.h
> --- include/cpu.h 6 Jul 2021 09:34:07 -0000 1.31
> +++ include/cpu.h 25 Jul 2022 00:30:33 -0000
> @@ -74,9 +74,9 @@ struct cpu_info {
> uint64_t ci_lasttb;
> uint64_t ci_nexttimerevent;
> uint64_t ci_nextstatevent;
> - int ci_statspending;
>
> volatile int ci_cpl;
> + volatile int ci_dec_deferred;
> uint32_t ci_ipending;
> uint32_t ci_idepth;
> #ifdef DIAGNOSTIC
> Index: powerpc64/clock.c
> ===================================================================
> RCS file: /cvs/src/sys/arch/powerpc64/powerpc64/clock.c,v
> retrieving revision 1.3
> diff -u -p -r1.3 clock.c
> --- powerpc64/clock.c 23 Feb 2021 04:44:31 -0000 1.3
> +++ powerpc64/clock.c 25 Jul 2022 00:30:33 -0000
> @@ -130,30 +130,23 @@ decr_intr(struct trapframe *frame)
> mtdec(nextevent - tb);
> mtdec(nextevent - mftb());
>
> - if (ci->ci_cpl >= IPL_CLOCK) {
> - ci->ci_statspending += nstats;
> - } else {
> - nstats += ci->ci_statspending;
> - ci->ci_statspending = 0;
> + s = splclock();
> + intr_enable();
>
> - s = splclock();
> - intr_enable();
> -
> - /*
> - * Do standard timer interrupt stuff.
> - */
> - while (ci->ci_lasttb < prevtb) {
> - ci->ci_lasttb += tick_increment;
> - clock_count.ec_count++;
> - hardclock((struct clockframe *)frame);
> - }
> + /*
> + * Do standard timer interrupt stuff.
> + */
> + while (ci->ci_lasttb < prevtb) {
> + ci->ci_lasttb += tick_increment;
> + clock_count.ec_count++;
> + hardclock((struct clockframe *)frame);
> + }
>
> - while (nstats-- > 0)
> - statclock((struct clockframe *)frame);
> + while (nstats-- > 0)
> + statclock((struct clockframe *)frame);
>
> - intr_disable();
> - splx(s);
> - }
> + intr_disable();
> + splx(s);
> }
>
> void
> Index: powerpc64/intr.c
> ===================================================================
> RCS file: /cvs/src/sys/arch/powerpc64/powerpc64/intr.c,v
> retrieving revision 1.9
> diff -u -p -r1.9 intr.c
> --- powerpc64/intr.c 26 Sep 2020 17:56:54 -0000 1.9
> +++ powerpc64/intr.c 25 Jul 2022 00:30:33 -0000
> @@ -139,6 +139,11 @@ splx(int new)
> {
> struct cpu_info *ci = curcpu();
>
> + if (ci->ci_dec_deferred && new < IPL_CLOCK) {
> + mtdec(0);
> + mtdec(UINT32_MAX); /* raise DEC exception */
> + }
> +
> if (ci->ci_ipending & intr_smask[new])
> intr_do_pending(new);
>
> Index: powerpc64/trap.c
> ===================================================================
> RCS file: /cvs/src/sys/arch/powerpc64/powerpc64/trap.c,v
> retrieving revision 1.51
> diff -u -p -r1.51 trap.c
> --- powerpc64/trap.c 11 May 2021 18:21:12 -0000 1.51
> +++ powerpc64/trap.c 25 Jul 2022 00:30:33 -0000
> @@ -65,9 +65,15 @@ trap(struct trapframe *frame)
> switch (type) {
> case EXC_DECR:
> uvmexp.intrs++;
> - ci->ci_idepth++;
> - decr_intr(frame);
> - ci->ci_idepth--;
> + if (ci->ci_cpl < IPL_CLOCK) {
> + ci->ci_dec_deferred = 0;
> + ci->ci_idepth++;
> + decr_intr(frame);
> + ci->ci_idepth--;
> + } else {
> + ci->ci_dec_deferred = 1;
> + mtdec(UINT32_MAX >> 1); /* clear DEC exception */
> + }
> return;
> case EXC_EXI:
> uvmexp.intrs++;
>
>
