xv6/spinlock.c
2006-07-17 05:00:25 +00:00

52 lines
860 B
C

#include "types.h"
#include "defs.h"
#include "x86.h"
#include "mmu.h"
#include "param.h"
#include "proc.h"
#include "spinlock.h"
// Can't call cprintf from inside these routines,
// because cprintf uses them itself.
#define cprintf dont_use_cprintf
extern int use_console_lock;
int
getcallerpc(void *v)
{
return ((int*)v)[-1];
}
void
acquire(struct spinlock * lock)
{
if(holding(lock))
panic("acquire");
if(cpus[cpu()].nlock++ == 0)
cli();
while(cmpxchg(0, 1, &lock->locked) == 1)
;
cpuid(0, 0, 0, 0, 0); // memory barrier
lock->pc = getcallerpc(&lock);
lock->cpu = cpu();
}
void
release(struct spinlock * lock)
{
if(!holding(lock))
panic("release");
cpuid(0, 0, 0, 0, 0); // memory barrier
lock->locked = 0;
if(--cpus[cpu()].nlock == 0)
sti();
}
int
holding(struct spinlock *lock)
{
return lock->locked && lock->cpu == cpu();
}