Release gvl while doing (f)stat

At the moment rb_stat function is blocking. This patch changes the
behaviour to release the gvl while waiting for OS to return from
f(stat).

There is behaviour impact, but not significant (times are for 100000
iterations):

   $ ~/releaseruby_patch/bin/ruby bench.rb
Rehearsal ------------------------------------------------
File.exist?:   0.036412   0.056616   0.093028 (  0.093075)
--------------------------------------- total: 0.093028sec

                   user     system      total        real
File.exist?:   0.042953   0.049783   0.092736 (  0.092804)

   $ ~/releaseruby_no_patch/bin/ruby bench.rb
Rehearsal ------------------------------------------------
File.exist?:   0.056094   0.026293   0.082387 (  0.082389)
--------------------------------------- total: 0.082387sec

                   user     system      total        real
File.exist?:   0.037250   0.046702   0.083952 (  0.083956)

Based on the patch by Wolf <wolf@wolfsden.cz> at [ruby-core:83012],
with using `rb_thread_io_blocking_region` for `fstat`.
[Bug #13941]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60027 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

common.mk

@@ -1757,6 +1757,7 @@ file.$(OBJEXT): {$(VPATH)}onigmo.h
 file.$(OBJEXT): {$(VPATH)}oniguruma.h
 file.$(OBJEXT): {$(VPATH)}st.h
 file.$(OBJEXT): {$(VPATH)}subst.h
+file.$(OBJEXT): {$(VPATH)}thread.h
 file.$(OBJEXT): {$(VPATH)}util.h
 gc.$(OBJEXT): $(CCAN_DIR)/check_type/check_type.h
 gc.$(OBJEXT): $(CCAN_DIR)/container_of/container_of.h

file.c

@@ -27,6 +27,7 @@
 #include "internal.h"
 #include "ruby/io.h"
 #include "ruby/util.h"
+#include "ruby/thread.h"
 #include "dln.h"
 #include "encindex.h"
 
@@ -1022,21 +1023,50 @@ rb_stat_inspect(VALUE self)
     return str;
 }
 
+typedef struct no_gvl_stat_data {
+    struct stat *st;
+    union {
+	const char *path;
+	int fd;
+    } file;
+} no_gvl_stat_data;
+
+static VALUE
+no_gvl_fstat(void *data)
+{
+    no_gvl_stat_data *arg = data;
+    return (VALUE)fstat(arg->file.fd, arg->st);
+}
+
+static void *
+no_gvl_stat(void * data)
+{
+    no_gvl_stat_data *arg = data;
+    return (void *)(VALUE)STAT(arg->file.path, arg->st);
+}
+
 static int
 rb_stat(VALUE file, struct stat *st)
 {
     VALUE tmp;
+    VALUE result;
+    no_gvl_stat_data data;
 
+    data.st = st;
     tmp = rb_check_convert_type_with_id(file, T_FILE, "IO", idTo_io);
     if (!NIL_P(tmp)) {
 	rb_io_t *fptr;
 
 	GetOpenFile(tmp, fptr);
-	return fstat(fptr->fd, st);
+	data.file.fd = fptr->fd;
+	result = rb_thread_io_blocking_region(no_gvl_fstat, &data, fptr->fd);
+	return (int)result;
     }
     FilePathValue(file);
     file = rb_str_encode_ospath(file);
-    return STAT(StringValueCStr(file), st);
+    data.file.path = StringValueCStr(file);
+    result = (VALUE)rb_thread_call_without_gvl(no_gvl_stat, &data, RUBY_UBF_IO, NULL);
+    return (int)result;
 }
 
 #ifdef _WIN32