52 lines
1.1 KiB
C
52 lines
1.1 KiB
C
#include "types.h"
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#include "defs.h"
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#include "x86.h"
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#include "mmu.h"
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#include "param.h"
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#include "proc.h"
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#include "spinlock.h"
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#define DEBUG 0
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int getcallerpc(void *v) {
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return ((int*)v)[-1];
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}
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void
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acquire(struct spinlock * lock)
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{
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struct proc * cp = curproc[cpu()];
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// on a real machine there would be a memory barrier here
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if(DEBUG) cprintf("cpu%d: acquiring at %x\n", cpu(), getcallerpc(&lock));
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if (cp && lock->p == cp && lock->locked){
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lock->count += 1;
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} else {
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cli();
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while ( cmpxchg(0, 1, &lock->locked) != 1 ) { ; }
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lock->locker_pc = getcallerpc(&lock);
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lock->count = 1;
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lock->p = cp;
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}
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if(DEBUG) cprintf("cpu%d: acquired at %x\n", cpu(), getcallerpc(&lock));
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}
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void
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release(struct spinlock * lock)
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{
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struct proc * cp = curproc[cpu()];
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if(DEBUG) cprintf ("cpu%d: releasing at %x\n", cpu(), getcallerpc(&lock));
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if(lock->p != cp || lock->count < 1 || lock->locked != 1)
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panic("release");
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lock->count -= 1;
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if(lock->count < 1){
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lock->p = 0;
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cmpxchg(1, 0, &lock->locked);
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sti();
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// on a real machine there would be a memory barrier here
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}
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}
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