blob: f82838fd9b7309f5509864a090efefb776d1b5f0 [file] [log] [blame]
/*
* Copyright 2017, Data61
* Commonwealth Scientific and Industrial Research Organisation (CSIRO)
* ABN 41 687 119 230.
*
* This software may be distributed and modified according to the terms of
* the BSD 2-Clause license. Note that NO WARRANTY is provided.
* See "LICENSE_BSD2.txt" for details.
*
* @TAG(DATA61_BSD)
*/
#include <autoconf.h>
#include <sync/recursive_mutex.h>
#include <stddef.h>
#include <assert.h>
#include <limits.h>
#include <sel4/sel4.h>
static void *thread_id(void)
{
return (void *)seL4_GetIPCBuffer();
}
int sync_recursive_mutex_init(sync_recursive_mutex_t *mutex, seL4_CPtr notification)
{
if (mutex == NULL) {
ZF_LOGE("Mutex passed to sync_recursive_mutex_init is NULL");
return -1;
}
#ifdef CONFIG_DEBUG_BUILD
/* Check the cap actually is a notification. */
assert(seL4_DebugCapIdentify(notification) == 6);
#endif
mutex->notification.cptr = notification;
mutex->owner = NULL;
mutex->held = 0;
/* Prime the endpoint. */
seL4_Signal(mutex->notification.cptr);
return 0;
}
int sync_recursive_mutex_lock(sync_recursive_mutex_t *mutex)
{
if (mutex == NULL) {
ZF_LOGE("Mutex passed to sync_recursive_mutex_lock is NULL");
return -1;
}
if (thread_id() != mutex->owner) {
/* We don't already have the mutex. */
seL4_Wait(mutex->notification.cptr, NULL);
__atomic_thread_fence(__ATOMIC_ACQUIRE);
assert(mutex->owner == NULL);
mutex->owner = thread_id();
assert(mutex->held == 0);
}
if (mutex->held == UINT_MAX) {
/* We would overflow if we re-acquired the mutex. Note that we can only
* be in this branch if we already held the mutex before entering this
* function, so we don't need to release the mutex here.
*/
return -1;
}
mutex->held++;
return 0;
}
int sync_recursive_mutex_unlock(sync_recursive_mutex_t *mutex)
{
if (mutex == NULL) {
ZF_LOGE("Mutex passed to sync_recursive_mutex_lock is NULL");
return -1;
}
assert(mutex->owner == thread_id());
assert(mutex->held > 0);
mutex->held--;
if (mutex->held == 0) {
/* This was the outermost lock we held. Wake the next person up. */
__atomic_store_n(&mutex->owner, NULL, __ATOMIC_RELEASE);
seL4_Signal(mutex->notification.cptr);
}
return 0;
}
int sync_recursive_mutex_new(vka_t *vka, sync_recursive_mutex_t *mutex)
{
int error = vka_alloc_notification(vka, &(mutex->notification));
if (error != 0) {
return error;
} else {
return sync_recursive_mutex_init(mutex, mutex->notification.cptr);
}
}
int sync_recursive_mutex_destroy(vka_t *vka, sync_recursive_mutex_t *mutex)
{
vka_free_object(vka, &(mutex->notification));
return 0;
}