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.
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//#define cprintf dont_use_cprintf
extern int use_console_lock;
int
getcallerpc(void *v)
{
return ((int*)v)[-1];
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}
void
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acquire(struct spinlock * lock)
{
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if(holding(lock)){
extern use_console_lock;
use_console_lock = 0;
cprintf("lock %s pc %x\n", lock->name ? lock->name : "", lock->pc);
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panic("acquire");
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}
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if(cpus[cpu()].nlock++ == 0)
cli();
while(cmpxchg(0, 1, &lock->locked) == 1)
;
cpuid(0, 0, 0, 0, 0); // memory barrier
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lock->pc = getcallerpc(&lock);
lock->cpu = cpu();
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cpus[cpu()].lastacquire = lock;
}
void
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release(struct spinlock * lock)
{
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if(!holding(lock))
panic("release");
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cpus[cpu()].lastrelease = lock;
cpuid(0, 0, 0, 0, 0); // memory barrier
lock->locked = 0;
if(--cpus[cpu()].nlock == 0)
sti();
}
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int
holding(struct spinlock *lock)
{
return lock->locked && lock->cpu == cpu();
}