Date: Sun, 29 Sep 1996 00:43:05 +0900 From: Hidetoshi Shimokawa <simokawa@sat.t.u-tokyo.ac.jp> To: freebsd-smp@freebsd.org Subject: Re: Tyan S1662 Titan Pro Message-ID: <1957.843925385@sat.t.u-tokyo.ac.jp>
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Hi, this is my first mail to freebsd-smp.
I finally succeeded to run smp-kernel on Tyan S1662 Titan Pro yesterday.
It needs some efforts to run stably.
As you know, the main problem is that boot cpu id is not 0 but 1.
I made some fixes against current smp code (no test1 or test2).
- change CPUNBR in mpcore.c
- stop cpu0 when smp is inactive in init_main.c
- tsleep when boot() is called on cpu0 in kern_shutdown.c
these changes are trivial, ad-hoc, and not generic.
With only above changes, the kernel had difficuties to change
smp_acitve value.
It often causes problem in shutdown sequence.
I don't know why, but while system is idle, processes is likely to run
on cpu0. So boot() in kern_shutdown is usually called on cpu0 and
it will do tsleep, but cpu1 never comes up.
I guess if boot cpu id is 0, boot() is usually called on boot cpu and
it doesn't matter at all.
I looked into this problem and I found a potential bug in handing
smp_atctive. Here is the code from init_main.c (I added BOOTCPU macro)
if ((smp_active == 0) && (cpunumber() != BOOTCPU)) {
get_mplock();
printf("cpu#%d freezing; mp_lock: %08x\n",cpunumber(), \
mp_lock);
wakeup((caddr_t)&smp_active);
rel_mplock();
....
this code is excuted when smp_active = 0, but when smp_active = 0,
get_mplock does nothing :-( (look at MPgetlock in mplock.s).
I think this causes the problem.
my solution is..
- introduce new state smp_active=1, this means only boot cpu is
allowed to run, and when boot() is called, smp_active is set to 1.
smp_active is 0 only after booting up and once second cpu is lunched,
smp_active should change among 1 and 2.
I'm not familiar with kernel prgramming, MP and even assembler,
I may be misunderstanding something.
FYI,
host: jp.freebsd.org
Tyan S1662 Titan Pro
2 PentiumPro (256KB cache, 233MHz overclocking :-)
To build SMP kernel with NetBSD make
168.004s real 238.468s user 70.809s system 184% pmake -j 6
Diffs, have a fun!
*** i386/i386/mpcore.s.orig Thu Sep 12 11:40:59 1996
--- i386/i386/mpcore.s Fri Sep 27 02:02:33 1996
***************
*** 159,167 ****
movsb
ret
- /*
#define CPUNBR 0x00000000
- */
#ifndef CPUNBR
#define CPUNBR 0x01000000
--- 159,165 ----
*** kern/init_main.c.orig Thu Sep 12 11:41:16 1996
--- kern/init_main.c Sat Sep 28 15:40:17 1996
***************
*** 719,731 ****
rel_mplock();
while (1) {
! if (smp_active == 0 && cpunumber() != 0) {
get_mplock();
printf("cpu#%d freezing; mp_lock: %08x\n", cpunumber(), mp_lock);
wakeup((caddr_t)&smp_active);
rel_mplock();
! while (smp_active == 0) {
__asm __volatile("" : : : "memory");
}
get_mplock();
--- 719,732 ----
rel_mplock();
while (1) {
! #define BOOTCPU 1
! if ((smp_active == 1) && (cpunumber() != BOOTCPU)) {
get_mplock();
printf("cpu#%d freezing; mp_lock: %08x\n", cpunumber(), mp_lock);
wakeup((caddr_t)&smp_active);
rel_mplock();
! while (smp_active < 2) {
__asm __volatile("" : : : "memory");
}
get_mplock();
*** kern/kern_shutdown.c.orig Thu Sep 12 11:41:17 1996
--- kern/kern_shutdown.c Fri Sep 27 22:50:38 1996
***************
*** 171,181 ****
#ifdef SMP
int c, spins;
- smp_active = 0;
spins = 100;
printf("boot() called on cpu#%d\n", cpunumber());
! while ((c = cpunumber()) != 0) {
if (spins-- < 1) {
printf("timeout waiting for cpu zero!\n");
break;
--- 171,183 ----
#ifdef SMP
int c, spins;
spins = 100;
+ if (smp_active) smp_active = 1;
+
printf("boot() called on cpu#%d\n", cpunumber());
! #define BOOTCPU 1
! while ((c = cpunumber()) != BOOTCPU) {
if (spins-- < 1) {
printf("timeout waiting for cpu zero!\n");
break;
/\ Hidetoshi Shimokawa
\/ simokawa@sat.t.u-tokyo.ac.jp
PGP public key: finger -l simokawa@sat.t.u-tokyo.ac.jp
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