2 * @brief Thread functions.
10 #include "threads-model.h"
13 /* global "model" object */
16 /** Allocate a stack for a new thread. */
17 static void * stack_allocate(size_t size)
19 return snapshot_malloc(size);
22 /** Free a stack for a terminated thread. */
23 static void stack_free(void *stack)
29 * @brief Get the current Thread
31 * Must be called from a user context
33 * @return The currently executing thread
35 Thread * thread_current(void)
38 return model->get_current_thread();
42 * Provides a startup wrapper for each thread, allowing some initial
43 * model-checking data to be recorded. This method also gets around makecontext
44 * not being 64-bit clean
48 Thread * curr_thread = thread_current();
50 /* Add dummy "start" action, just to create a first clock vector */
51 model->switch_to_master(new ModelAction(THREAD_START, std::memory_order_seq_cst, curr_thread));
53 /* Call the actual thread function */
54 curr_thread->start_routine(curr_thread->arg);
56 /* Finish thread properly */
57 model->switch_to_master(new ModelAction(THREAD_FINISH, std::memory_order_seq_cst, curr_thread));
61 * Create a thread context for a new thread so we can use
62 * setcontext/getcontext/swapcontext to swap it out.
63 * @return 0 on success; otherwise, non-zero error condition
65 int Thread::create_context()
69 ret = getcontext(&context);
73 /* Initialize new managed context */
74 stack = stack_allocate(STACK_SIZE);
75 context.uc_stack.ss_sp = stack;
76 context.uc_stack.ss_size = STACK_SIZE;
77 context.uc_stack.ss_flags = 0;
78 context.uc_link = model->get_system_context();
79 makecontext(&context, thread_startup, 0);
85 * Swaps the current context to another thread of execution. This form switches
86 * from a user Thread to a system context.
87 * @param t Thread representing the currently-running thread. The current
88 * context is saved here.
89 * @param ctxt Context to which we will swap. Must hold a valid system context.
90 * @return Does not return, unless we return to Thread t's context. See
91 * swapcontext(3) (returns 0 for success, -1 for failure).
93 int Thread::swap(Thread *t, ucontext_t *ctxt)
95 t->set_state(THREAD_READY);
96 return model_swapcontext(&t->context, ctxt);
100 * Swaps the current context to another thread of execution. This form switches
101 * from a system context to a user Thread.
102 * @param ctxt System context variable to which to save the current context.
103 * @param t Thread to which we will swap. Must hold a valid user context.
104 * @return Does not return, unless we return to the system context (ctxt). See
105 * swapcontext(3) (returns 0 for success, -1 for failure).
107 int Thread::swap(ucontext_t *ctxt, Thread *t)
109 t->set_state(THREAD_RUNNING);
110 return model_swapcontext(ctxt, &t->context);
114 /** Terminate a thread and free its stack. */
115 void Thread::complete()
117 ASSERT(!is_complete());
118 DEBUG("completed thread %d\n", id_to_int(get_id()));
119 state = THREAD_COMPLETED;
125 * @brief Construct a new model-checker Thread
127 * A model-checker Thread is used for accounting purposes only. It will never
128 * have its own stack, and it should never be inserted into the Scheduler.
130 * @param tid The thread ID to assign
132 Thread::Thread(thread_id_t tid) :
141 state(THREAD_READY), /* Thread is always ready? */
145 memset(&context, 0, sizeof(context));
149 * Construct a new thread.
150 * @param t The thread identifier of the newly created thread.
151 * @param func The function that the thread will call.
152 * @param a The parameter to pass to this function.
154 Thread::Thread(thrd_t *t, void (*func)(void *), void *a, Thread *parent) :
161 state(THREAD_CREATED),
162 last_action_val(VALUE_NONE),
167 /* Initialize state */
168 ret = create_context();
170 model_print("Error in create_context\n");
172 id = model->get_next_id();
173 user_thread->priv = this;
183 /** @return The thread_id_t corresponding to this Thread object. */
184 thread_id_t Thread::get_id() const
190 * Set a thread's THREAD_* state (@see thread_state)
191 * @param s The state to enter
193 void Thread::set_state(thread_state s)
195 ASSERT(s == THREAD_COMPLETED || state != THREAD_COMPLETED);
200 * Get the Thread that this Thread is immediately waiting on
201 * @return The thread we are waiting on, if any; otherwise NULL
203 Thread * Thread::waiting_on() const
208 if (pending->get_type() == THREAD_JOIN)
209 return pending->get_thread_operand();
210 else if (pending->is_lock())
211 return (Thread *)pending->get_mutex()->get_state()->locked;
216 * Check if this Thread is waiting (blocking) on a given Thread, directly or
217 * indirectly (via a chain of waiting threads)
219 * @param t The Thread on which we may be waiting
220 * @return True if we are waiting on Thread t; false otherwise
222 bool Thread::is_waiting_on(const Thread *t) const
225 for (wait = waiting_on(); wait != NULL; wait = wait->waiting_on())