Introduce `Fiber::Scheduler#blocking_operation_wait`. (#12016)

Redirect `rb_nogvl` blocking operations to the fiber scheduler if possible
to prevent stalling the event loop.

[Feature #20876]

1 files changed, 14 insertions, 0 deletions

diff --git a/thread.c b/thread.c
index 64ada750b6..86c7392e9c 100644
--- a/thread.c
+++ b/thread.c
@@ -1539,6 +1539,20 @@ rb_nogvl(void *(*func)(void *), void *data1,
          rb_unblock_function_t *ubf, void *data2,
          int flags)
 {
+    if (flags & RB_NOGVL_OFFLOAD_SAFE) {
+        VALUE scheduler = rb_fiber_scheduler_current();
+        if (scheduler != Qnil) {
+            struct rb_fiber_scheduler_blocking_operation_state state;
+
+            VALUE result = rb_fiber_scheduler_blocking_operation_wait(scheduler, func, data1, ubf, data2, flags, &state);
+
+            if (!UNDEF_P(result)) {
+                rb_errno_set(state.saved_errno);
+                return state.result;
+            }
+        }
+    }
+
     void *val = 0;
     rb_execution_context_t *ec = GET_EC();
     rb_thread_t *th = rb_ec_thread_ptr(ec);