dir.c: release GVL around remaining readdir calls

Release GVL around all remaining readdir calls from the Dir
class to prevent pathological stalls on slow filesystems in
multi-threaded applications.

opendir, rewinddir, closedir calls are not affected yet, but
will be changed in future commits.

In the future, further work may be done consolidate multiple GVL
releasing calls to reduce overhead, similar to how changes to
Dir.empty? were made in r60111

* dir.c (nogvl_readdir): new function
  (readdir_without_gvl): ditto
  (dir_read): s/READDIR/readdir_without_gvl/
  (dir_each_entry): ditto
  (glob_helper): ditto

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@60769 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

dir.c

@@ -743,6 +743,20 @@ to_be_skipped(const struct dirent *dp)
     return FALSE;
 }
 
+static void *
+nogvl_readdir(void *ptr)
+{
+    struct dir_data *dirp = ptr;
+
+    return READDIR(dirp->dir, dirp->enc);
+}
+
+static struct dirent *
+readdir_without_gvl(struct dir_data *dirp)
+{
+    return rb_thread_call_without_gvl(nogvl_readdir, dirp, RUBY_UBF_IO, 0);
+}
+
 /*
  *  call-seq:
  *     dir.read -> string or nil
@@ -763,7 +777,7 @@ dir_read(VALUE dir)
 
     GetDIR(dir, dirp);
     errno = 0;
-    if ((dp = READDIR(dirp->dir, dirp->enc)) != NULL) {
+    if ((dp = readdir_without_gvl(dirp))) {
 	return rb_external_str_new_with_enc(dp->d_name, NAMLEN(dp), dirp->enc);
     }
     else {
@@ -818,7 +832,7 @@ dir_each_entry(VALUE dir, VALUE (*each)(VALUE, VALUE), VALUE arg, int children_o
     GetDIR(dir, dirp);
     rewinddir(dirp->dir);
     IF_NORMALIZE_UTF8PATH(norm_p = need_normalization(dirp->dir, RSTRING_PTR(dirp->path)));
-    while ((dp = READDIR(dirp->dir, dirp->enc)) != NULL) {
+    while ((dp = readdir_without_gvl(dirp)) != NULL) {
 	const char *name = dp->d_name;
 	size_t namlen = NAMLEN(dp);
 	VALUE path;
@@ -2006,25 +2020,27 @@ glob_helper(
     if (pathtype == path_noent) return 0;
 
     if (magical || recursive) {
+	struct dir_data dd;
 	struct dirent *dp;
-	DIR *dirp;
 # if USE_NAME_ON_FS == USE_NAME_ON_FS_BY_FNMATCH
 	char *plainname = 0;
 # endif
 	IF_NORMALIZE_UTF8PATH(int norm_p);
+
+	dd.enc = enc;
 # if USE_NAME_ON_FS == USE_NAME_ON_FS_BY_FNMATCH
 	if (cur + 1 == end && (*cur)->type <= ALPHA) {
 	    plainname = join_path(path, pathlen, dirsep, (*cur)->str, strlen((*cur)->str));
 	    if (!plainname) return -1;
-	    dirp = do_opendir(fd, plainname, flags, enc, funcs->error, arg, &status);
+	    dd.dir = do_opendir(fd, plainname, flags, enc, funcs->error, arg, &status);
 	    GLOB_FREE(plainname);
 	}
 	else
 # else
 	    ;
 # endif
-	dirp = do_opendir(fd, *base ? base : ".", flags, enc, funcs->error, arg, &status);
-	if (dirp == NULL) {
+	dd.dir = do_opendir(fd, *base ? base : ".", flags, enc, funcs->error, arg, &status);
+	if (dd.dir == NULL) {
 # if FNM_SYSCASE || NORMALIZE_UTF8PATH
 	    if ((magical < 2) && !recursive && (errno == EACCES)) {
 		/* no read permission, fallback */
@@ -2033,19 +2049,19 @@ glob_helper(
 # endif
 	    return status;
 	}
-	IF_NORMALIZE_UTF8PATH(norm_p = need_normalization(dirp, *base ? base : "."));
+	IF_NORMALIZE_UTF8PATH(norm_p = need_normalization(dd.dir, *base ? base : "."));
 
 # if NORMALIZE_UTF8PATH
 	if (!(norm_p || magical || recursive)) {
-	    closedir(dirp);
+	    closedir(dd.dir);
 	    goto literally;
 	}
 # endif
 # ifdef HAVE_GETATTRLIST
-	if (is_case_sensitive(dirp, path) == 0)
+	if (is_case_sensitive(dd.dir, path) == 0)
 	    flags |= FNM_CASEFOLD;
 # endif
-	while ((dp = READDIR(dirp, enc)) != NULL) {
+	while ((dp = readdir_without_gvl(&dd)) != NULL) {
 	    char *buf;
 	    rb_pathtype_t new_pathtype = path_unknown;
 	    const char *name;
@@ -2140,7 +2156,7 @@ glob_helper(
 	    if (status) break;
 	}
 
-	closedir(dirp);
+	closedir(dd.dir);
     }
     else if (plain) {
 	struct glob_pattern **copy_beg, **copy_end, **cur2;