Implement pthread_cancel.

core/sys/unix/pthread_darwin.odin

@@ -81,3 +81,16 @@ PTHREAD_MUTEX_NORMAL :: 0
 PTHREAD_MUTEX_RECURSIVE :: 1
 PTHREAD_MUTEX_ERRORCHECK :: 2
 
+PTHREAD_CANCEL_ENABLE       :: 0
+PTHREAD_CANCEL_DISABLE      :: 1
+PTHREAD_CANCEL_DEFERRED     :: 0
+PTHREAD_CANCEL_ASYNCHRONOUS :: 1
+
+foreign import pthread "System.framework"
+
+@(default_calling_convention="c")
+foreign pthread {
+	pthread_setcancelstate :: proc (state: c.int, old_state: ^c.int) -> c.int ---
+	pthread_setcanceltype  :: proc (type:  c.int, old_type:  ^c.int) -> c.int ---
+	pthread_cancel         :: proc (thread: pthread_t) -> c.int ---
+}

core/sys/unix/pthread_freebsd.odin

@@ -92,6 +92,11 @@ sem_t :: struct {
 	_padding: u32,
 }
 
+PTHREAD_CANCEL_ENABLE       :: 0
+PTHREAD_CANCEL_DISABLE      :: 1
+PTHREAD_CANCEL_DEFERRED     :: 0
+PTHREAD_CANCEL_ASYNCHRONOUS :: 1
+
 foreign import "system:pthread"
 
 @(default_calling_convention="c")
@@ -110,5 +115,8 @@ foreign pthread {
 	// NOTE: unclear whether pthread_yield is well-supported on Linux systems,
 	// see https://linux.die.net/man/3/pthread_yield
 	pthread_yield :: proc() ---
-}
 
+	pthread_setcancelstate :: proc (state: c.int, old_state: ^c.int) -> c.int ---
+	pthread_setcanceltype  :: proc (type:  c.int, old_type:  ^c.int) -> c.int ---
+	pthread_cancel         :: proc (thread: pthread_t) -> c.int ---
+}

core/sys/unix/pthread_linux.odin

@@ -94,6 +94,11 @@ when size_of(int) == 8 {
 	SEM_T_SIZE :: 16
 }
 
+PTHREAD_CANCEL_ENABLE       :: 0
+PTHREAD_CANCEL_DISABLE      :: 1
+PTHREAD_CANCEL_DEFERRED     :: 0
+PTHREAD_CANCEL_ASYNCHRONOUS :: 1
+
 foreign import "system:pthread"
 
 @(default_calling_convention="c")
@@ -112,4 +117,8 @@ foreign pthread {
 	// NOTE: unclear whether pthread_yield is well-supported on Linux systems,
 	// see https://linux.die.net/man/3/pthread_yield
 	pthread_yield :: proc() -> c.int ---
+
+	pthread_setcancelstate :: proc (state: c.int, old_state: ^c.int) -> c.int ---
+	pthread_setcanceltype  :: proc (type:  c.int, old_type:  ^c.int) -> c.int ---
+	pthread_cancel         :: proc (thread: pthread_t) -> c.int ---
 }

core/sys/unix/pthread_openbsd.odin

@@ -46,6 +46,11 @@ sched_param :: struct {
 
 sem_t :: distinct rawptr
 
+PTHREAD_CANCEL_ENABLE       :: 0
+PTHREAD_CANCEL_DISABLE      :: 1
+PTHREAD_CANCEL_DEFERRED     :: 0
+PTHREAD_CANCEL_ASYNCHRONOUS :: 1
+
 foreign import libc "system:c"
 
 @(default_calling_convention="c")
@@ -62,4 +67,8 @@ foreign libc {
 	// NOTE: unclear whether pthread_yield is well-supported on Linux systems,
 	// see https://linux.die.net/man/3/pthread_yield
 	pthread_yield :: proc() ---
-}
+
+	pthread_setcancelstate :: proc (state: c.int, old_state: ^c.int) -> c.int ---
+	pthread_setcanceltype  :: proc (type:  c.int, old_type:  ^c.int) -> c.int ---
+	pthread_cancel         :: proc (thread: pthread_t) -> c.int ---
+}

core/thread/thread_unix.odin

@@ -31,6 +31,9 @@ _create :: proc(procedure: Thread_Proc, priority := Thread_Priority.Normal) -> ^
 	__linux_thread_entry_proc :: proc "c" (t: rawptr) -> rawptr {
 		t := (^Thread)(t)
 
+		// We need to give the thread a moment to start up before we enable cancellation.
+		can_set_thread_cancel_state := unix.pthread_setcancelstate(unix.PTHREAD_CANCEL_DISABLE, nil) == 0
+
 		context = runtime.default_context()
 
 		sync.lock(&t.mutex)
@@ -44,6 +47,12 @@ _create :: proc(procedure: Thread_Proc, priority := Thread_Priority.Normal) -> ^
 		init_context := t.init_context
 		context =	init_context.? or_else runtime.default_context()
 
+		// Enable thread's cancelability.
+		if can_set_thread_cancel_state {
+			unix.pthread_setcanceltype (unix.PTHREAD_CANCEL_ASYNCHRONOUS, nil)
+			unix.pthread_setcancelstate(unix.PTHREAD_CANCEL_DISABLE,      nil)
+		}
+
 		t.procedure(t)
 
 		intrinsics.atomic_store(&t.flags, t.flags + { .Done })
@@ -141,7 +150,7 @@ _destroy :: proc(t: ^Thread) {
 }
 
 _terminate :: proc(t: ^Thread, exit_code: int) {
-	// TODO(bill)
+	unix.pthread_cancel(t.unix_thread)
 }
 
 _yield :: proc() {

examples/demo/demo.odin

@@ -1110,9 +1110,16 @@ prefix_table := [?]string{
 	"Black",
 }
 
+print_mutex := b64(false)
+
 threading_example :: proc() {
 	fmt.println("\n# threading_example")
 
+	did_acquire :: proc(m: ^b64) -> (acquired: bool) {
+		res, ok := intrinsics.atomic_compare_exchange_strong(m, false, true)
+		return ok && res == false
+	}
+
 	{ // Basic Threads
 		fmt.println("\n## Basic Threads")
 		worker_proc :: proc(t: ^thread.Thread) {
@@ -1154,14 +1161,21 @@ threading_example :: proc() {
 		task_proc :: proc(t: thread.Task) {
 			index := t.user_index % len(prefix_table)
 			for iteration in 1..=5 {
+				for !did_acquire(&print_mutex) { thread.yield() } // Allow one thread to print at a time.
+
 				fmt.printf("Worker Task %d is on iteration %d\n", t.user_index, iteration)
 				fmt.printf("`%s`: iteration %d\n", prefix_table[index], iteration)
+
+				print_mutex = false
+
 				time.sleep(1 * time.Millisecond)
 			}
 		}
 
+		N :: 3
+
 		pool: thread.Pool
-		thread.pool_init(pool=&pool, thread_count=3, allocator=context.allocator)
+		thread.pool_init(pool=&pool, thread_count=N, allocator=context.allocator)
 		defer thread.pool_destroy(&pool)
 
 
@@ -1171,6 +1185,19 @@ threading_example :: proc() {
 		}
 
 		thread.pool_start(&pool)
+
+		{
+			// Wait a moment before we cancel a thread
+			time.sleep(5 * time.Millisecond)
+
+			// Allow one thread to print at a time.
+			for !did_acquire(&print_mutex) { thread.yield() }
+
+			thread.terminate(pool.threads[N - 1], 0)
+			fmt.println("Canceled last thread")
+			print_mutex = false
+		}
+
 		thread.pool_finish(&pool)
 	}
 }