xv6/spinlock.c

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#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
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extern int bootstrap;
int
getcallerpc(void *v)
{
return ((int*)v)[-1];
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}
void
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acquire(struct spinlock * lock)
{
if(cpus[cpu()].nlock++ == 0)
cli();
while(cmpxchg(0, 1, &lock->locked) == 1)
;
cpuid(0, 0, 0, 0, 0); // memory barrier
lock->locker_pc = getcallerpc(&lock);
}
void
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release(struct spinlock * lock)
{
cpuid(0, 0, 0, 0, 0); // memory barrier
lock->locked = 0;
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if(--cpus[cpu()].nlock == 0 && !bootstrap)
sti();
}