Date: Wed, 25 Jun 1997 20:32:35 -0600 From: Steve Passe <smp@csn.net> To: Christopher Ulbright <ulbright@cs.washington.edu> Cc: freebsd-smp@FreeBSD.ORG Subject: Re: Debugger Message-ID: <199706260232.UAA17883@Ilsa.StevesCafe.com> In-Reply-To: Your message of "Wed, 25 Jun 1997 09:50:19 PDT." <Pine.OSF.3.96.970625094314.9321B-100000@sanjuan.cs.washington.edu>
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Hi,
some suggested pseudo-code follows. please comment.
------------------------------------- cut -------------------------------------
---
/*
* example usage:
*/
breakpoint()
{
...
stop_other_cpus(cpu_map);
do_stuff();
restart_other_cpus(stopped_cpus);
...
}
---
i386/include/smp.h:
/* global data in i386/isa/apic_vector.s: */
extern volatile u_int stopped_cpus;
extern volatile u_int started_cpus;
extern u_int cpu_map;
---
i386/isa/intr_machdep.h:
#define XCPUSTOP_OFFSET 33
inthand_t
Xcpustop;
---
i386/i386/mp_machdep.c:
/*
* existing functions:
*/
mp_enable(u_int boot_addr)
{
...
#if defined( APIC_IO )
...
+ /* install an inter-CPU IPI for CPU stop/restart */
+ setidt(ICU_OFFSET + XCPUSTOP_OFFSET, Xcpustop,
+ SDT_SYS386IGT, SEL_KPL, GSEL(GCODE_SEL, SEL_KPL));
#endif /* APIC_IO */
...
}
start_all_aps(u_int boot_addr)
{
...
/* start each AP */
for (x = 1; x <= mp_naps; ++x) {
...
+ cpu_map |= (1 << x); /* record AP in global map */
}
...
+ cpu_map |= 1; /* record BSP in global map */
}
/*
* new functions:
*/
/*
* When called the executing CPU will send an IPI to all other CPUs
* requesting that they halt execution.
*
* Usually (but not necessarily) called with 'cpu_map' as its arg.
*
* - Signals all CPUs in map to stop.
* - Waits for each to stop.
*
* Returns:
* -1: error
* 0: NA
* 1: ok
*
* XXX FIXME: this is not MP-safe, needs a lock to prevent multiple CPUs
* from executing at same time.
*/
int
stop_other_cpus( u_int map )
{
if (!smp_active)
return 0;
stopped_cpus = 0;
map &= ~(1 << cpuid); /* clear our bit */
/* send IPI to all CPUs in map */
selected_apic_ipi(map,
ICU_OFFSET + XSTOP_CPUS_OFFSET,
APIC_DELMODE_FIXED);
while (stopped_cpus != map)
/* spin */ ;
return 1;
}
/*
* Called by a CPU to restart stopped CPUs.
*
* Usually (but not necessarily) called with 'stopped_cpus' as its arg.
*
* - Signals all CPUs in map to restart.
* - Waits for each to restart.
*
* Returns:
* -1: error
* 0: NA
* 1: ok
*/
int
restart_other_cpus( u_int map )
{
if (!smp_active)
return 0;
map &= ~(1 << cpuid); /* XXX paranoia */
started_cpus = map; /* signal other cpus to restart */
while (started_cpus) /* wait for each to clear its bit */
/* spin */ ;
return 1;
}
---
i386/isa/apic_vector.s:
.globl _stopped_cpus
_stopped_cpus:
.long 0
.globl _started_cpus
_started_cpus:
.long 0
.globl _cpu_map
_cpu_map:
.long 0
/*
* Executed by a CPU when it receives an Xcpustop IPI from another CPU,
*
* - Signals its receipt.
* - Waits for permission to restart.
* - Signals its restart.
*/
.text
SUPERALIGN_TEXT
.globl _Xcpustop
_Xcpustop:
pushl %eax
pushl %ds /* save current data segment */
movl $KDSEL, %eax
movl %ax, %ds /* use KERNEL data segment */
movl _cpuid, %eax /* id */
lock
btsl %eax, _stopped_cpus /* stopped_cpus |= (1<<id) */
1:
btl %eax, _started_cpus /* while (!(started_cpus & (1<<id))) */
jnc 1b
lock
btrl %eax, _started_cpus /* started_cpus &= ~(1<<id) */
popl %ds /* restore previous data segment */
popl %eax
iret
------------------------------------- cut -------------------------------------
--
Steve Passe | powered by
smp@csn.net | Symmetric MultiProcessor FreeBSD
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