mutex.c

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#include <kernel/acpi/aml/runtime/mutex.h>
 
#include <kernel/log/log.h>
#include <kernel/sched/sched.h>
#include <kernel/sched/thread.h>
 
#include <errno.h>
#include <stdlib.h>
 
typedef struct
{
    list_entry_t entry;
    aml_mutex_id_t id;
    aml_sync_level_t syncLevel;
} aml_mutex_entry_t;
 
static bool initialized = false;
static aml_sync_level_t currentSyncLevel = 0;
static list_t mutexStack;
 
static atomic_int32_t newMutexId = ATOMIC_VAR_INIT(1);
 
static inline uint64_t aml_mutex_stack_push(aml_mutex_id_t id, aml_sync_level_t syncLevel)
{
    if (!initialized)
    {
        list_init(&mutexStack);
        initialized = true;
    }
 
    if (syncLevel < currentSyncLevel)
    {
        LOG_ERR("Attempted to acquire a mutex with a lower SyncLevel than the current SyncLevel\n");
        errno = EDEADLK;
        return ERR;
    }
 
    aml_mutex_entry_t* entry = malloc(sizeof(aml_mutex_entry_t));
    if (entry == NULL)
    {
        return ERR;
    }
    list_entry_init(&entry->entry);
    entry->id = id;
    entry->syncLevel = syncLevel;
 
    list_push(&mutexStack, &entry->entry);
    currentSyncLevel = syncLevel;
    return 0;
}
 
static inline uint64_t aml_mutex_stack_pop(aml_mutex_id_t id)
{
    if (list_length(&mutexStack) == 0)
    {
        LOG_ERR("Attempted to release a mutex when none are held\n");
        errno = EDEADLK;
        return ERR;
    }
 
    aml_mutex_entry_t* topEntry = CONTAINER_OF(list_last(&mutexStack), aml_mutex_entry_t, entry);
    if (topEntry->id != id)
    {
        LOG_ERR("Mutex release not in LIFO order\n");
        errno = EDEADLK;
        return ERR;
    }
 
    list_remove(&mutexStack, &topEntry->entry);
    free(topEntry);
 
    if (list_length(&mutexStack) == 0)
    {
        currentSyncLevel = 0;
    }
    else
    {
        aml_mutex_entry_t* newTopEntry = CONTAINER_OF(list_last(&mutexStack), aml_mutex_entry_t, entry);
        currentSyncLevel = newTopEntry->syncLevel;
    }
    return 0;
}
 
void aml_mutex_id_init(aml_mutex_id_t* mutex)
{
    *mutex = atomic_fetch_add(&newMutexId, 1);
}
 
void aml_mutex_id_deinit(aml_mutex_id_t* mutex)
{
    *mutex = 0;
}
 
uint64_t aml_mutex_acquire(aml_mutex_id_t* mutex, aml_sync_level_t syncLevel, clock_t timeout)
{
    (void)timeout; // We ignore timeouts since we have the big mutex.
 
    if (mutex == NULL)
    {
        errno = EINVAL;
        return ERR;
    }
 
    // As mentioned, mutexes arent implemented since we have the big mutex, so we just pretend that
    // we acquired it immediately.
 
    if (aml_mutex_stack_push(*mutex, syncLevel) == ERR)
    {
        return ERR;
    }
    return 0;
}
 
uint64_t aml_mutex_release(aml_mutex_id_t* mutex)
{
    if (mutex == NULL)
    {
        errno = EINVAL;
        return ERR;
    }
 
    if (aml_mutex_stack_pop(*mutex) == ERR)
    {
        return ERR;
    }
    return 0;
}