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, 41 insertions, 0 deletions

diff --git a/ext/-test-/gvl/call_without_gvl/call_without_gvl.c b/ext/-test-/gvl/call_without_gvl/call_without_gvl.c
index f3071d5768..654c979479 100644
--- a/ext/-test-/gvl/call_without_gvl/call_without_gvl.c
+++ b/ext/-test-/gvl/call_without_gvl/call_without_gvl.c
@@ -27,8 +27,49 @@ thread_runnable_sleep(VALUE thread, VALUE timeout)
     return thread;
 }
 
+struct loop_ctl {
+    int notify_fd;
+    volatile int stop;
+};
+
+static void *
+do_loop(void *p)
+{
+    struct loop_ctl *ctl = p;
+
+    /* tell the waiting process they can interrupt us, now */
+    write(ctl->notify_fd, "", 1);
+
+    while (!ctl->stop) {
+        struct timeval tv = { 0, 10000 };
+        select(0, NULL, NULL, NULL, &tv);
+    }
+    return 0;
+}
+
+static void
+stop_set(void *p)
+{
+    struct loop_ctl *ctl = p;
+
+    ctl->stop = 1;
+}
+
+static VALUE
+thread_ubf_async_safe(VALUE thread, VALUE notify_fd)
+{
+    struct loop_ctl ctl;
+
+    ctl.notify_fd = NUM2INT(notify_fd);
+    ctl.stop = 0;
+
+    rb_nogvl(do_loop, &ctl, stop_set, &ctl, RB_NOGVL_UBF_ASYNC_SAFE);
+    return thread;
+}
+
 void
 Init_call_without_gvl(void)
 {
     rb_define_method(rb_cThread, "__runnable_sleep__", thread_runnable_sleep, 1);
+    rb_define_method(rb_cThread, "__ubf_async_safe__", thread_ubf_async_safe, 1);
 }