introduce rb_nogvl C-API to mark ubf as async-signal-safe

zlib and bignum both contain unblocking functions which are
async-signal-safe and do not require spawning additional
threads.

We can execute those functions directly in signal handlers
without incurring overhead of extra threads, so provide C-API
users the ability to deal with that.  Other C-API users may
have similar need.

This flexible API can supercede existing uses of
rb_thread_call_without_gvl and rb_thread_call_without_gvl2 by
introducing a flags argument to control behavior.

Note: this API is NOT finalized.  It needs approval from other
committers.  I prefer shorter name than previous
rb_thread_call_without_gvl* functions because my eyes requires
big fonts.

[Bug #15499]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66712 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 16 insertions, 8 deletions

diff --git a/thread.c b/thread.c
index 06fd49cf2c..59935a2e1c 100644
--- a/thread.c
+++ b/thread.c
@@ -1421,9 +1421,10 @@ blocking_region_end(rb_thread_t *th, struct rb_blocking_region_buffer *region)
     }
 }
 
-static void *
-call_without_gvl(void *(*func)(void *), void *data1,
-		 rb_unblock_function_t *ubf, void *data2, int fail_if_interrupted)
+void *
+rb_nogvl(void *(*func)(void *), void *data1,
+         rb_unblock_function_t *ubf, void *data2,
+         int flags)
 {
     void *val = 0;
     rb_execution_context_t *ec = GET_EC();
@@ -1436,15 +1437,22 @@ call_without_gvl(void *(*func)(void *), void *data1,
 	data2 = th;
     }
     else if (ubf && vm_living_thread_num(th->vm) == 1) {
-        ubf_th = rb_thread_start_unblock_thread();
+        if (RB_NOGVL_UBF_ASYNC_SAFE) {
+            th->vm->ubf_async_safe = 1;
+        }
+        else {
+            ubf_th = rb_thread_start_unblock_thread();
+        }
     }
 
     BLOCKING_REGION(th, {
 	val = func(data1);
 	saved_errno = errno;
-    }, ubf, data2, fail_if_interrupted);
+    }, ubf, data2, flags & RB_NOGVL_INTR_FAIL);
+
+    th->vm->ubf_async_safe = 0;
 
-    if (!fail_if_interrupted) {
+    if ((flags & RB_NOGVL_INTR_FAIL) == 0) {
 	RUBY_VM_CHECK_INTS_BLOCKING(ec);
     }
 
@@ -1546,14 +1554,14 @@ void *
 rb_thread_call_without_gvl2(void *(*func)(void *), void *data1,
 			    rb_unblock_function_t *ubf, void *data2)
 {
-    return call_without_gvl(func, data1, ubf, data2, TRUE);
+    return rb_nogvl(func, data1, ubf, data2, RB_NOGVL_INTR_FAIL);
 }
 
 void *
 rb_thread_call_without_gvl(void *(*func)(void *data), void *data1,
 			    rb_unblock_function_t *ubf, void *data2)
 {
-    return call_without_gvl(func, data1, ubf, data2, FALSE);
+    return rb_nogvl(func, data1, ubf, data2, 0);
 }
 
 VALUE