semaphore.h File Reference

#include <sys/queue.h>
#include <sys/spinlock.h>

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Data Structures
struct	Semaphore

Macros
#define	SEMAPHORE_NAMELEN   32

Typedefs
typedef struct Semaphore	Semaphore

Functions
void	Semaphore_Init (Semaphore *sema, int count, const char *name)
void	Semaphore_Destroy (Semaphore *sema)
void	Semaphore_Acquire (Semaphore *sema)
void	Semaphore_Release (Semaphore *sema)
bool	Semaphore_TryAcquire (Semaphore *sema)

Macro Definition Documentation

SEMAPHORE_NAMELEN

#define SEMAPHORE_NAMELEN   32

Definition at line 8 of file semaphore.h.

Typedef Documentation

Semaphore

typedef struct Semaphore Semaphore

Function Documentation

Semaphore_Acquire()

void Semaphore_Acquire

(

Semaphore *

sema

)

Definition at line 49 of file semaphore.c.

{
    Thread *cur = Sched_Current();
 
    while (1) {
        Spinlock_Lock(&sema->lock);
        if (sema->count > 0) {
            sema->count -= 1;
            Spinlock_Unlock(&sema->lock);
            Thread_Release(cur);
            return;
        }
 
        // Add to sleeper list
        TAILQ_INSERT_TAIL(&sema->waiters, cur, semaQueue);
        Sched_SetWaiting(cur);
 
        Spinlock_Unlock(&sema->lock);
        Sched_Scheduler();
    }
}

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Semaphore_Destroy()

void Semaphore_Destroy

(

Semaphore *

sema

)

Definition at line 39 of file semaphore.c.

{
    Spinlock_Lock(&semaListLock);
    LIST_REMOVE(sema, semaphoreList);
    Spinlock_Unlock(&semaListLock);
 
    Spinlock_Destroy(&sema->lock);
}

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Semaphore_Init()

void Semaphore_Init	(	Semaphore *	sema,
		int	count,
		const char *	name
	)

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Semaphore_Release()

void Semaphore_Release

(

Semaphore *

sema

)

Definition at line 72 of file semaphore.c.

{
    Thread *thr;
 
    Spinlock_Lock(&sema->lock);
    sema->count += 1;
 
    // Wakeup thread
    thr = TAILQ_FIRST(&sema->waiters);
    if (thr != NULL) {
        TAILQ_REMOVE(&sema->waiters, thr, semaQueue);
        Sched_SetRunnable(thr);
    }
    Spinlock_Unlock(&sema->lock);
}

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Semaphore_TryAcquire()

bool Semaphore_TryAcquire

(

Semaphore *

sema

)

Definition at line 89 of file semaphore.c.

{
    Spinlock_Lock(&sema->lock);
    if (sema->count > 0) {
        sema->count -= 1;
        Spinlock_Unlock(&sema->lock);
        return true;
    }
    Spinlock_Unlock(&sema->lock);
    return false;
}

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