i think my cmpxchg use was wrong in acquire

nesting cli/sti: release shouldn't always enable interrupts
separate setup of lapic from starting of other cpus, so cpu() works earlier
flag to disable locking in console output
make locks work even when curproc==0
(still crashes in clock interrupt)
This commit is contained in:
rtm 2006-07-12 11:15:38 +00:00
parent 664324745e
commit 8148b6ee53
11 changed files with 85 additions and 32 deletions

4
Notes
View file

@ -125,6 +125,10 @@ in general, the table locks protect both free-ness and
why can't i get a lock in console code?
always triple fault
because release turns on interrupts!
a bad idea very early in main()
but mp_init() calls cprintf
lock code shouldn't call cprintf...
ide_init doesn't work now?
and IOAPIC: read from unsupported address

View file

@ -4,6 +4,7 @@
#include "spinlock.h"
struct spinlock console_lock;
int use_printf_lock = 0;
/*
* copy console output to parallel port, which you can tell
@ -29,7 +30,8 @@ cons_putc(int c)
unsigned short *crt = (unsigned short *) 0xB8000; // base of CGA memory
int ind;
//acquire(&console_lock);
if(use_printf_lock)
acquire(&console_lock);
lpt_putc(c);
@ -62,7 +64,8 @@ cons_putc(int c)
outb(crtport, 15);
outb(crtport + 1, ind);
//release(&console_lock);
if(use_printf_lock)
release(&console_lock);
}
void
@ -127,6 +130,8 @@ cprintf(char *fmt, ...)
void
panic(char *s)
{
use_printf_lock = 0;
cprintf("panic: ");
cprintf(s, 0);
cprintf("\n", 0);
while(1)

3
defs.h
View file

@ -19,6 +19,8 @@ void wakeup(void *);
void scheduler(void);
void proc_exit(void);
void yield(void);
void cli(void);
void sti(void);
// swtch.S
struct jmpbuf;
@ -46,6 +48,7 @@ void pic_init(void);
// mp.c
void mp_init(void);
void mp_startthem(void);
int cpu(void);
int mp_isbcpu(void);
void lapic_init(int);

View file

@ -10,6 +10,9 @@
#include "param.h"
#include "types.h"
#include "defs.h"
#include "param.h"
#include "mmu.h"
#include "proc.h"
#include "spinlock.h"
struct spinlock kalloc_lock;

13
main.c
View file

@ -8,6 +8,7 @@
#include "syscall.h"
#include "elf.h"
#include "param.h"
#include "spinlock.h"
extern char edata[], end[];
extern int acpu;
@ -15,23 +16,33 @@ extern char _binary_user1_start[], _binary_user1_size[];
extern char _binary_usertests_start[], _binary_usertests_size[];
extern char _binary_userfs_start[], _binary_userfs_size[];
extern use_printf_lock;
int
main()
{
struct proc *p;
if (acpu) {
cpus[cpu()].clis = 1;
cprintf("an application processor\n");
idtinit(); // CPU's idt
lapic_init(cpu());
lapic_timerinit();
lapic_enableintr();
sti();
scheduler();
}
acpu = 1;
// clear BSS
memset(edata, 0, end - edata);
mp_init(); // just set up apic so cpu() works
use_printf_lock = 1;
cpus[cpu()].clis = 1; // cpu starts as if we had called cli()
cprintf("\nxV6\n\n");
pic_init(); // initialize PIC
@ -56,7 +67,7 @@ main()
p->ppid = 0;
setupsegs(p);
mp_init(); // multiprocessor
mp_startthem();
// turn on timer and enable interrupts on the local APIC
lapic_timerinit();

11
mp.c
View file

@ -325,8 +325,6 @@ mp_init()
struct MPCTB *mpctb;
struct MPPE *proc;
struct MPBE *bus;
int c;
extern int main();
int i;
ncpu = 0;
@ -386,13 +384,20 @@ mp_init()
lapic_init(bcpu-cpus);
cprintf("ncpu: %d boot %d\n", ncpu, bcpu-cpus);
}
void
mp_startthem()
{
extern uint8_t _binary_bootother_start[], _binary_bootother_size[];
extern int main();
int c;
memmove((void *) APBOOTCODE,_binary_bootother_start,
(uint32_t) _binary_bootother_size);
for(c = 0; c < ncpu; c++){
if (cpus+c == bcpu) continue;
if (c == cpu()) continue;
cprintf ("starting processor %d\n", c);
*(unsigned *)(APBOOTCODE-4) = (unsigned) (cpus[c].mpstack) + MPSTACK; // tell it what to use for %esp
*(unsigned *)(APBOOTCODE-8) = (unsigned)&main; // tell it where to jump to

25
proc.c
View file

@ -148,6 +148,7 @@ scheduler(void)
if(i < NPROC){
np->state = RUNNING;
release(&proc_table_lock);
break;
}
@ -157,8 +158,6 @@ scheduler(void)
cpus[cpu()].lastproc = np;
curproc[cpu()] = np;
release(&proc_table_lock);
// h/w sets busy bit in TSS descriptor sometimes, and faults
// if it's set in LTR. so clear tss descriptor busy bit.
@ -252,3 +251,25 @@ proc_exit()
// switch into scheduler
swtch(ZOMBIE);
}
// disable interrupts
void
cli(void)
{
cpus[cpu()].clis += 1;
if(cpus[cpu()].clis == 1)
__asm __volatile("cli");
}
// enable interrupts
void
sti(void)
{
if(cpus[cpu()].clis < 1){
cprintf("cpu %d clis %d\n", cpu(), cpus[cpu()].clis);
panic("sti");
}
cpus[cpu()].clis -= 1;
if(cpus[cpu()].clis < 1)
__asm __volatile("sti");
}

1
proc.h
View file

@ -69,6 +69,7 @@ struct cpu {
struct jmpbuf jmpbuf;
char mpstack[MPSTACK]; // per-cpu start-up stack, only used to get into main()
struct proc *lastproc; // last proc scheduled on this cpu (never NULL)
int clis; // cli() nesting depth
};
extern struct cpu cpus[NCPU];

View file

@ -8,6 +8,8 @@
#define DEBUG 0
extern use_printf_lock;
int getcallerpc(void *v) {
return ((int*)v)[-1];
}
@ -15,37 +17,49 @@ int getcallerpc(void *v) {
void
acquire(struct spinlock * lock)
{
struct proc * cp = curproc[cpu()];
unsigned who;
if(curproc[cpu()])
who = (unsigned) curproc[cpu()];
else
who = cpu() + 1;
// on a real machine there would be a memory barrier here
if(DEBUG) cprintf("cpu%d: acquiring at %x\n", cpu(), getcallerpc(&lock));
if (cp && lock->p == cp && lock->locked){
if (lock->who == who && lock->locked){
lock->count += 1;
} else {
cli();
while ( cmpxchg(0, 1, &lock->locked) != 1 ) { ; }
// if we get the lock, eax will be zero
// if we don't get the lock, eax will be one
while ( cmpxchg(0, 1, &lock->locked) == 1 ) { ; }
lock->locker_pc = getcallerpc(&lock);
lock->count = 1;
lock->p = cp;
lock->who = who;
}
if(DEBUG) cprintf("cpu%d: acquired at %x\n", cpu(), getcallerpc(&lock));
}
void
release(struct spinlock * lock)
{
struct proc * cp = curproc[cpu()];
unsigned who;
if(curproc[cpu()])
who = (unsigned) curproc[cpu()];
else
who = cpu() + 1;
if(DEBUG) cprintf ("cpu%d: releasing at %x\n", cpu(), getcallerpc(&lock));
if(lock->p != cp || lock->count < 1 || lock->locked != 1)
if(lock->who != who || lock->count < 1 || lock->locked != 1)
panic("release");
lock->count -= 1;
if(lock->count < 1){
lock->p = 0;
lock->who = 0;
cmpxchg(1, 0, &lock->locked);
sti();
// on a real machine there would be a memory barrier here
}
}

View file

@ -1,6 +1,6 @@
struct spinlock {
unsigned int locked;
struct proc *p;
unsigned who;
int count;
unsigned locker_pc;
};

14
x86.h
View file

@ -304,20 +304,6 @@ read_tsc(void)
return tsc;
}
// disable interrupts
static __inline void
cli(void)
{
__asm __volatile("cli");
}
// enable interrupts
static __inline void
sti(void)
{
__asm __volatile("sti");
}
struct PushRegs {
/* registers as pushed by pusha */
uint32_t reg_edi;