| /* |
| * 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; |
| } |