Add a test for the task scanner.

test/gcext/gcext.c

@@ -454,6 +454,67 @@ void root_scanner(int full)
  }
 }
 
+// Test stack direction
+static int is_lower_stack_frame(volatile char *frame_addr) {
+ volatile char buf[1];
+ return (uintptr_t) buf < (uintptr_t) frame_addr;
+}
+
+typedef volatile int (*volatile test_frame_func)(volatile char *frame_addr);
+
+// To prevent inlining, we make this a volatile function pointer.
+
+static test_frame_func is_lower_stack_frame_ptr =
+ (test_frame_func) is_lower_stack_frame;
+
+static int stack_grows_down(void) {
+ volatile char buf[1];
+ return is_lower_stack_frame_ptr(buf);
+}
+
+void task_scanner(jl_task_t *task, int root_task)
+{
+ // The task scanner is not necessary for liveness, as the
+ // corresponding task stack is already part of the stack.
+ // Its purpose is simply to test that the task scanner
+ // doing actual work does not trigger a problem.
+ size_t size;
+ int tid;
+ void *stack = jl_task_stack_buffer(task, &size, &tid);
+ if (tid >= 0) {
+ // this is the live stack of a thread. Is it ours?
+ if (stack && tid == jl_threadid()) {
+ // only scan the live portion of the stack.
+ char *end_stack = (char *) stack + size;
+ if (lt_ptr(stack, &size) && lt_ptr(&size, (char *)stack + size)) {
+ if (stack_grows_down()) {
+ size = end_stack - (char *)&size;
+ stack = (void *)&size;
+ }
+ else {
+ size = (char *) end_stack - (char *) &size;
+ }
+ } else {
+ // error, current stack frame must be on the live stack.
+ jl_error("stack frame not part of the current task");
+ }
+ }
+ else
+ stack = NULL;
+ }
+ if (stack) {
+ void **start = (void **) stack;
+ void **end = start + size / sizeof(void *);
+ while (start < end) {
+ void *p = *start++;
+ void *q = jl_gc_internal_obj_base_ptr(p);
+ if (q) {
+ jl_gc_mark_queue_obj(ptls, q);
+ }
+ }
+ }
+}
+
 // Hooks to run before and after GC.
 //
 // As a simple example, we only track counters for full
@@ -545,6 +606,7 @@ int main()
  abort();
  ptls = jl_get_ptls_states();
  jl_gc_set_cb_root_scanner(root_scanner, 1);
+ jl_gc_set_cb_task_scanner(task_scanner, 1);
  jl_gc_set_cb_pre_gc(pre_gc_func, 1);
  jl_gc_set_cb_post_gc(post_gc_func, 1);
  // Test that deregistration works