ladybird/Libraries/LibPthread/pthread.cpp

#include <AK/Assertions.h>
#include <AK/Atomic.h>
#include <AK/StdLibExtras.h>
#include <Kernel/Syscall.h>
#include <pthread.h>
#include <stdio.h>
#include <sys/mman.h>
#include <unistd.h>

extern "C" {

static int create_thread(void* (*entry)(void*), void* argument, void* stack)
{
    int rc = syscall(SC_create_thread, entry, argument, stack);
    __RETURN_WITH_ERRNO(rc, rc, -1);
}

static void exit_thread(void* code)
{
    syscall(SC_exit_thread, code);
    ASSERT_NOT_REACHED();
}

int pthread_create(pthread_t* thread, pthread_attr_t* attributes, void* (*start_routine)(void*), void* argument_to_start_routine)
{
    if (!thread)
        return -EINVAL;
    UNUSED_PARAM(attributes);
    const size_t stack_size = 4 * MB;
    auto* stack = (u8*)mmap_with_name(nullptr, stack_size, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANONYMOUS | MAP_STACK, 0, 0, "Thread stack");
    if (!stack)
        return -1;
    int rc = create_thread(start_routine, argument_to_start_routine, stack + stack_size);
    if (rc < 0)
        return rc;
    *thread = rc;
    return 0;
}

void pthread_exit(void* value_ptr)
{
    exit_thread(value_ptr);
}

int pthread_join(pthread_t thread, void** exit_value_ptr)
{
    int rc = syscall(SC_join_thread, thread, exit_value_ptr);
    __RETURN_WITH_ERRNO(rc, rc, -1);
}

int pthread_mutex_init(pthread_mutex_t* mutex, const pthread_mutexattr_t* attributes)
{
    // FIXME: Implement mutex attributes
    UNUSED_PARAM(attributes);
    *mutex = 0;
    return 0;
}

int pthread_mutex_lock(pthread_mutex_t* mutex)
{
    auto* atomic = reinterpret_cast<Atomic<u32>*>(mutex);
    for (;;) {
        u32 expected = false;
        if (atomic->compare_exchange_strong(expected, true, AK::memory_order_acq_rel))
            return 0;
        sched_yield();
    }
}

int pthread_mutex_unlock(pthread_mutex_t* mutex)
{
    auto* atomic = reinterpret_cast<Atomic<u32>*>(mutex);
    atomic->store(false, AK::memory_order_release);
    return 0;
}
}