fiddle: release GVL for ffi_call

Some external functions I wish to call may take a long time
and unnecessarily block other threads.  This may lead to performance
regressions for fast functions as releasing/acquiring the GVL is not
cheap, but can improve performance for long-running functions
in multi-threaded applications.

This also means we must reacquire the GVL when calling Ruby-defined
callbacks for Fiddle::Closure, meaning we must detect whether the
current thread has the GVL by exporting ruby_thread_has_gvl_p
in internal.h

* ext/fiddle/function.c (struct nogvl_ffi_call_args):
  new struct for GVL release
  (nogvl_ffi_call): new function
  (function_call): adjust for GVL release
  [ruby-core:71642] [Feature #11607]
* ext/fiddle/closure.c (struct callback_args):
  new struct for GVL acquire
  (with_gvl_callback): adjusted original callback function
  (callback): wrapper for conditional GVL acquire
* ext/fiddle/depend: add dependencies
* ext/fiddle/extconf.rb: include top_srcdir for internal.h
* internal.h (ruby_thread_has_gvl_p): expose for fiddle
* vm_core.h (ruby_thread_has_gvl_p): moved to internal.h
* test/fiddle/test_function.rb (test_nogvl_poll): new test

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52723 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 19 insertions, 0 deletions

diff --git a/test/fiddle/test_function.rb b/test/fiddle/test_function.rb
index 2e3a432ec3..9351f961df 100644
--- a/test/fiddle/test_function.rb
+++ b/test/fiddle/test_function.rb
@@ -73,6 +73,25 @@ module Fiddle
       assert_equal("123", str.to_s)
     end
 
+    def test_nogvl_poll
+      begin
+        poll = @libc['poll']
+      rescue Fiddle::DLError
+        skip 'poll(2) not available'
+      end
+      f = Function.new(poll, [TYPE_VOIDP, TYPE_INT, TYPE_INT], TYPE_INT)
+
+      msec = 200
+      t0 = Process.clock_gettime(Process::CLOCK_MONOTONIC, :millisecond)
+      th = Thread.new { f.call(nil, 0, msec) }
+      n1 = f.call(nil, 0, msec)
+      n2 = th.value
+      t1 = Process.clock_gettime(Process::CLOCK_MONOTONIC, :millisecond)
+      assert_in_delta(msec, t1 - t0, 100, 'slept correct amount of time')
+      assert_equal(0, n1, 'poll(2) called correctly main-thread')
+      assert_equal(0, n2, 'poll(2) called correctly in sub-thread')
+    end
+
     def test_no_memory_leak
       prep = 'r = Fiddle::Function.new(Fiddle.dlopen(nil)["rb_obj_tainted"], [Fiddle::TYPE_UINTPTR_T], Fiddle::TYPE_UINTPTR_T); a = "a"'
       code = 'begin r.call(a); rescue TypeError; end'