Add option to jl_print_task_backtraces(bool) to control whether or …

…not to print DONE tasks (#47933)

Add option to `jl_print_task_backtraces(bool)` to control whether or not to print DONE tasks

This lets you print all live tasks, with less noise in the logs, in case
it's been a while since the last GC.

In some cases, we are seeing many thousands of DONE Tasks, which greatly
increase the noise in the logs, and can overwhelm the DataDog logging.

The API now takes a bool, which can allow us to control this setting, letting us print
the DONE tasks if the user wants to, but also hide them if desired.

(cherry picked from commit 8324512)

src/stackwalk.c

@@ -1126,7 +1126,7 @@ JL_DLLEXPORT void jl_print_backtrace(void) JL_NOTSAFEPOINT
 // Print backtraces for all live tasks, for all threads.
 // WARNING: this is dangerous and can crash if used outside of gdb, if
 // all of Julia's threads are not stopped!
-JL_DLLEXPORT void jl_print_task_backtraces(void) JL_NOTSAFEPOINT
+JL_DLLEXPORT void jl_print_task_backtraces(int show_done) JL_NOTSAFEPOINT
 {
     size_t nthreads = jl_atomic_load_acquire(&jl_n_threads);
     jl_ptls_t *allstates = jl_atomic_load_relaxed(&jl_all_tls_states);
@@ -1146,9 +1146,13 @@ JL_DLLEXPORT void jl_print_task_backtraces(void) JL_NOTSAFEPOINT
         void **lst = live_tasks->items;
         for (size_t j = 0; j < live_tasks->len; j++) {
             jl_task_t *t = (jl_task_t *)lst[j];
+            int t_state = jl_atomic_load_relaxed(&t->_state);
+            if (!show_done && t_state == JL_TASK_STATE_DONE) {
+                continue;
+            }
             jl_safe_printf("     ---- Task %zu (%p)\n", j + 1, t);
             jl_safe_printf("          (sticky: %d, started: %d, state: %d, tid: %d)\n",
-                    t->sticky, t->started, jl_atomic_load_relaxed(&t->_state),
+                    t->sticky, t->started, t_state,
                     jl_atomic_load_relaxed(&t->tid) + 1);
             if (t->stkbuf != NULL)
                 jlbacktracet(t);