create separate function to spawn GC threads

Author: d-netto

src/gc.c

@@ -3957,6 +3957,29 @@ void jl_free_thread_gc_state(jl_ptls_t ptls)
     arraylist_free(&mq->reclaim_set);
 }
 
+void jl_spawn_gc_threads(void)
+{
+    int nthreads = jl_atomic_load_relaxed(&jl_n_threads);
+    int ngcthreads = jl_n_gcthreads;
+    int nmutator_threads = nthreads - ngcthreads;
+    uv_thread_t uvtid;
+    for (int i = 1; i < nthreads; ++i) {
+        if (i < nmutator_threads) {
+            continue;
+        }
+        jl_threadarg_t *t = (jl_threadarg_t *)malloc_s(sizeof(jl_threadarg_t)); // ownership will be passed to the thread
+        t->tid = i;
+        t->barrier = &thread_init_done;
+        if (i == nthreads - 1 && jl_n_sweepthreads == 1) {
+            uv_thread_create(&uvtid, jl_concurrent_gc_threadfun, t);
+        }
+        else {
+            uv_thread_create(&uvtid, jl_parallel_gc_threadfun, t);
+        }
+        uv_thread_detach(&uvtid);
+    }
+}
+
 // System-wide initializations
 void jl_gc_init(void)
 {

src/gc.h

@@ -572,6 +572,7 @@ extern uv_cond_t gc_threads_cond;
 extern uv_sem_t gc_sweep_assists_needed;
 extern _Atomic(int) gc_n_threads_marking;
 extern _Atomic(int) gc_n_threads_sweeping;
+extern uv_barrier_t thread_init_done;
 void gc_mark_queue_all_roots(jl_ptls_t ptls, jl_gc_markqueue_t *mq);
 void gc_mark_finlist_(jl_gc_markqueue_t *mq, jl_value_t *fl_parent, jl_value_t **fl_begin, jl_value_t **fl_end) JL_NOTSAFEPOINT;
 void gc_mark_finlist(jl_gc_markqueue_t *mq, arraylist_t *list, size_t start) JL_NOTSAFEPOINT;

src/julia_internal.h

@@ -960,9 +960,10 @@ extern JL_DLLEXPORT ssize_t jl_tls_offset;
 extern JL_DLLEXPORT const int jl_tls_elf_support;
 void jl_init_threading(void);
 void jl_start_threads(void);
-extern uv_mutex_t safepoint_lock;
+void jl_spawn_gc_threads(void);
 
 // Whether the GC is running
+extern uv_mutex_t safepoint_lock;
 extern char *jl_safepoint_pages;
 STATIC_INLINE int jl_addr_is_safepoint(uintptr_t addr)
 {

src/threading.c

@@ -761,7 +761,7 @@ void jl_init_threading(void)
     gc_first_tid = nthreads + nthreadsi;
 }
 
-static uv_barrier_t thread_init_done;
+uv_barrier_t thread_init_done;
 
 void jl_start_threads(void)
 {
@@ -800,28 +800,23 @@ void jl_start_threads(void)
     uv_barrier_init(&thread_init_done, nthreads);
 
     // GC/System threads need to be after the worker threads.
-    int nworker_threads = nthreads - ngcthreads;
+    int nmutator_threads = nthreads - ngcthreads;
 
     for (i = 1; i < nthreads; ++i) {
-        jl_threadarg_t *t = (jl_threadarg_t *)malloc_s(sizeof(jl_threadarg_t)); // ownership will be passed to the thread
-        t->tid = i;
-        t->barrier = &thread_init_done;
-        if (i < nworker_threads) {
+        if (i < nmutator_threads) {
+            jl_threadarg_t *t = (jl_threadarg_t *)malloc_s(sizeof(jl_threadarg_t)); // ownership will be passed to the thread
+            t->tid = i;
+            t->barrier = &thread_init_done;
             uv_thread_create(&uvtid, jl_threadfun, t);
             if (exclusive) {
                 mask[i] = 1;
                 uv_thread_setaffinity(&uvtid, mask, NULL, cpumasksize);
                 mask[i] = 0;
             }
         }
-        else if (i == nthreads - 1 && jl_n_sweepthreads == 1) {
-            uv_thread_create(&uvtid, jl_concurrent_gc_threadfun, t);
-        }
-        else {
-            uv_thread_create(&uvtid, jl_parallel_gc_threadfun, t);
-        }
         uv_thread_detach(&uvtid);
     }
+    jl_spawn_gc_threads();
 
     uv_barrier_wait(&thread_init_done);
 }