remove a bunch of 'skip GC threads' checks since they now have tasks (#55160)

GC threads now have tasks (since
#53815).

Author: d-netto

src/gc-stacks.c

@@ -332,10 +332,6 @@ JL_DLLEXPORT jl_array_t *jl_live_tasks(void)
     size_t l = 0; // l is not reset on restart, so we keep getting more aggressive at making a big enough list everything it fails
 restart:
     for (size_t i = 0; i < nthreads; i++) {
-        // skip GC threads since they don't have tasks
-        if (gc_first_tid <= i && i < gc_first_tid + jl_n_gcthreads) {
-            continue;
-        }
         jl_ptls_t ptls2 = allstates[i];
         if (ptls2 == NULL)
             continue;
@@ -349,10 +345,6 @@ JL_DLLEXPORT jl_array_t *jl_live_tasks(void)
     allstates = jl_atomic_load_relaxed(&jl_all_tls_states);
     size_t j = 0;
     for (size_t i = 0; i < nthreads; i++) {
-        // skip GC threads since they don't have tasks
-        if (gc_first_tid <= i && i < gc_first_tid + jl_n_gcthreads) {
-            continue;
-        }
         jl_ptls_t ptls2 = allstates[i];
         if (ptls2 == NULL)
             continue;

src/gc.h

@@ -478,6 +478,16 @@ STATIC_INLINE int gc_is_parallel_collector_thread(int tid) JL_NOTSAFEPOINT
     return tid >= gc_first_tid && tid <= gc_last_parallel_collector_thread_id();
 }
 
+STATIC_INLINE int gc_is_concurrent_collector_thread(int tid) JL_NOTSAFEPOINT
+{
+    if (jl_n_sweepthreads == 0) {
+        return 0;
+    }
+    int last_parallel_collector_thread_id = gc_last_parallel_collector_thread_id();
+    int concurrent_collector_thread_id = last_parallel_collector_thread_id + 1;
+    return tid == concurrent_collector_thread_id;
+}
+
 STATIC_INLINE int gc_random_parallel_collector_thread_id(jl_ptls_t ptls) JL_NOTSAFEPOINT
 {
     assert(jl_n_markthreads > 0);

src/stackwalk.c

@@ -5,6 +5,7 @@
   utilities for walking the stack and looking up information about code addresses
 */
 #include <inttypes.h>
+#include "gc.h"
 #include "julia.h"
 #include "julia_internal.h"
 #include "threading.h"
@@ -1215,11 +1216,15 @@ 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);
     for (size_t i = 0; i < nthreads; i++) {
-        // skip GC threads since they don't have tasks
-        if (gc_first_tid <= i && i < gc_first_tid + jl_n_gcthreads) {
+        jl_ptls_t ptls2 = allstates[i];
+        if (gc_is_parallel_collector_thread(i)) {
+            jl_safe_printf("==== Skipping backtrace for parallel GC thread %zu\n", i + 1);
+            continue;
+        }
+        if (gc_is_concurrent_collector_thread(i)) {
+            jl_safe_printf("==== Skipping backtrace for concurrent GC thread %zu\n", i + 1);
             continue;
         }
-        jl_ptls_t ptls2 = allstates[i];
         if (ptls2 == NULL) {
             continue;
         }