63 lines
1.2 KiB
C
63 lines
1.2 KiB
C
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#include "config.h"
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#include "rwlock.h"
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#include "bool.h"
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#include "atomic.h"
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#include "threads.h"
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/* A simple spinlock. Yield the thread while the given integer is set by
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* another. Could probably be improved... */
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static void Lock(volatile int *l)
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{
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while(ExchangeInt(l, true) == true)
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althrd_yield();
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}
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static void Unlock(volatile int *l)
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{
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ExchangeInt(l, false);
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}
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void RWLockInit(RWLock *lock)
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{
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InitRef(&lock->read_count, 0);
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InitRef(&lock->write_count, 0);
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lock->read_lock = false;
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lock->read_entry_lock = false;
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lock->write_lock = false;
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}
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void ReadLock(RWLock *lock)
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{
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Lock(&lock->read_entry_lock);
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Lock(&lock->read_lock);
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if(IncrementRef(&lock->read_count) == 1)
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Lock(&lock->write_lock);
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Unlock(&lock->read_lock);
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Unlock(&lock->read_entry_lock);
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}
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void ReadUnlock(RWLock *lock)
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{
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if(DecrementRef(&lock->read_count) == 0)
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Unlock(&lock->write_lock);
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}
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void WriteLock(RWLock *lock)
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{
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if(IncrementRef(&lock->write_count) == 1)
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Lock(&lock->read_lock);
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Lock(&lock->write_lock);
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}
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void WriteUnlock(RWLock *lock)
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{
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Unlock(&lock->write_lock);
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if(DecrementRef(&lock->write_count) == 0)
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Unlock(&lock->read_lock);
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}
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