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#ifndef THREADS_SYNCH_H
#define THREADS_SYNCH_H
#include <list.h>
#include <stdbool.h>
/* A counting semaphore. */
struct semaphore
{
unsigned value; /* Current value. */
struct list waiters; /* List of waiting threads. */
};
void sema_init (struct semaphore *, unsigned value);
void sema_down (struct semaphore *);
bool sema_try_down (struct semaphore *);
void sema_up (struct semaphore *);
void sema_self_test (void);
/* Lock. */
struct lock
{
struct thread *holder; /* Thread holding lock (for debugging). */
struct semaphore semaphore; /* Binary semaphore controlling access. */
};
void lock_init (struct lock *);
void lock_acquire (struct lock *);
bool lock_try_acquire (struct lock *);
void lock_release (struct lock *);
bool lock_held_by_current_thread (const struct lock *);
/* Condition variable. */
struct condition
{
struct list waiters; /* List of waiting threads. */
};
void cond_init (struct condition *);
void cond_wait (struct condition *, struct lock *);
void cond_signal (struct condition *, struct lock *);
void cond_broadcast (struct condition *, struct lock *);
/* Readers-writers lock.
Implementation of "First readers-writers problem" from
https://en.wikipedia.org/wiki/Readers%E2%80%93writers_problem. */
struct rwlock
{
struct semaphore resource;
struct lock rmutex;
unsigned readcount;
};
void rwlock_init (struct rwlock *);
void rwlock_write_p (struct rwlock *);
void rwlock_write_v (struct rwlock *);
void rwlock_read_p (struct rwlock *);
void rwlock_read_v (struct rwlock *);
/* Optimization barrier.
The compiler will not reorder operations across an
optimization barrier. See "Optimization Barriers" in the
reference guide for more information.*/
#define barrier() asm volatile ("" : : : "memory")
#endif /* threads/synch.h */
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