pthread_mutex.c

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#include <sys/types.h>
#include <stdio.h>
#include <stddef.h>
#include <stdlib.h>
#include <errno.h>
#include <pthread.h>

#include <interrupt.h>

int pthread_mutex_destroy(pthread_mutex_t *mutex)
{
        /* Release locked process(or thread) */
        mutex->lock = 0;
        return 0;
}

int pthread_mutex_init(pthread_mutex_t *mutex,
                const pthread_mutexattr_t *attr)
{
        mutex->lock = 0;
        mutex->owner = NULL;
        mutex->refcnt = 0;
        return 0;
}

int pthread_mutex_lock(pthread_mutex_t *mutex)
{
        unsigned long flags;

        irq_local_save(&flags);
        if (pthread_equal(mutex->owner, pthread_self())) {
                mutex->refcnt++;
                irq_local_restore(flags);
                return 0;
        }
        irq_local_restore(flags);

        asm __volatile__ (
                "1:"
                "movl $0, %%eax;\n"
                "movl $1, %%ecx;\n"
                "lock; cmpxchgl %%ecx, %0;\n"
                "jz 2f;\n"
                "jmp 1b;\n"
                "2:\n"
                : "=m"(mutex->lock)
                :
                : "memory", "%ecx", "%eax"
        );

        mutex->owner = pthread_self();
        mutex->refcnt = 1;
        return 0;
}

int pthread_mutex_trylock(pthread_mutex_t *mutex)
{
        int ret;
        unsigned long flags;

        irq_local_save(&flags);
        if (pthread_equal(mutex->owner, pthread_self())) {
                mutex->refcnt++;
                irq_local_restore(flags);
                return 0;
        }
        irq_local_restore(flags);

        asm __volatile__ (
                "movl $0, %%eax;\n"
                "movl $1, %%ecx;\n"
                "lock; cmpxchgl %%ecx, %0;\n"
                "jz 2f;\n"
                "movl $-1, %1;\n"
                "jmp 3f\n"
                "2:\n"
                "movl $0, %1;\n"
                "3:\n"
                : "=m"(mutex->lock), "=m"(ret)
                :
                : "memory", "%ecx", "%eax"
        );

        if (ret < 0) {
                return ret;
        }

        mutex->owner = pthread_self();
        mutex->refcnt = 1;
        return ret;
}

int pthread_mutex_unlock(pthread_mutex_t *mutex)
{
        unsigned long flags;

        irq_local_save(&flags);
        if (!pthread_equal(mutex->owner, pthread_self())) {
                irq_local_restore(flags);
                return -EINVAL;
        }

        mutex->refcnt--;
        if (mutex->refcnt > 0) {
                irq_local_restore(flags);
                return 0;
        }
        irq_local_restore(flags);

        mutex->owner = NULL;
        asm __volatile__ (
                "movl $0, %%eax;\n"
                "xchgl %%eax, %0;\n"
                : "=m"(mutex->lock)
                :
                : "memory", "%eax"
        );

        return 0;
}

/* End of a file */