xv6/spinlock.c

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#include "types.h"
#include "defs.h"
#include "x86.h"
#define LOCK_FREE -1
uint32_t kernel_lock = LOCK_FREE;
// lock = LOCK_FREE if free, else = cpu_id of owner CPU
void
acquire_spinlock(uint32_t* lock)
{
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int cpu_id = cpu();
if (*lock == cpu_id)
return;
lapic_disableintr();
while ( cmpxchg(LOCK_FREE, cpu_id, lock) != cpu_id ) { ; }
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// cprintf ("acquired: %d\n", cpu_id);
}
void
release_spinlock(uint32_t* lock)
{
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int cpu_id = cpu();
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// cprintf ("release: %d\n", cpu_id);
if (*lock != cpu_id)
panic("release_spinlock: releasing a lock that i don't own\n");
*lock = LOCK_FREE;
lapic_enableintr();
}
void
release_grant_spinlock(uint32_t* lock, int c)
{
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int cpu_id = cpu();
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// cprintf ("release_grant: %d -> %d\n", cpu_id, c);
if (*lock != cpu_id)
panic("release_spinlock: releasing a lock that i don't own\n");
*lock = c;
}