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authorEric Wong <normalperson@yhbt.net>2014-01-01 09:50:15 +0000
committerEric Wong <normalperson@yhbt.net>2014-01-01 10:08:26 +0000
commit91613ed4880e793491dc2024725cbbcfdf64a7a9 (patch)
tree7c92afd6f7ae2edfd09e5765a5e71a8c5c75d013
parent728b2c70cda7787a80303c6fa2c2530dcb490c90 (diff)
Using thread-local storage via the Ruby API allows us to not worry
about memory management.
-rw-r--r--ext/unicorn_http/httpdate.c73
1 files changed, 62 insertions, 11 deletions
diff --git a/ext/unicorn_http/httpdate.c b/ext/unicorn_http/httpdate.c
index bf54fdd..06598e2 100644
--- a/ext/unicorn_http/httpdate.c
+++ b/ext/unicorn_http/httpdate.c
@@ -1,10 +1,9 @@
+#define RSTRING_MODIFIED 1 /* we modify RSTRING_PTR */
 #include <ruby.h>
 #include <time.h>
 #include <stdio.h>
 
 static const size_t buf_capa = sizeof("Thu, 01 Jan 1970 00:00:00 GMT");
-static VALUE buf;
-static char *buf_ptr;
 static const char week[] = "Sun\0Mon\0Tue\0Wed\0Thu\0Fri\0Sat";
 static const char months[] = "Jan\0Feb\0Mar\0Apr\0May\0Jun\0"
                              "Jul\0Aug\0Sep\0Oct\0Nov\0Dec";
@@ -21,6 +20,59 @@ static struct tm * my_gmtime_r(time_t *now, struct tm *tm)
 #  define gmtime_r my_gmtime_r
 #endif
 
+/* TODO: update this in case other implementations lose the GVL */
+#if defined(RUBINIUS)
+#  define UH_HAVE_GVL (0)
+#else
+#  define UH_HAVE_GVL (1)
+#endif
+
+#if defined(__GNUC__) && (__GNUC__ >= 3)
+# define UH_ATTRIBUTE_CONST __attribute__ ((__const__))
+#else
+# define UH_ATTRIBUTE_CONST /* empty */
+#endif
+
+#if UH_HAVE_GVL
+static VALUE g_buf;
+static char *g_buf_ptr;
+static VALUE UH_ATTRIBUTE_CONST get_buf(void) { return g_buf; }
+static char * UH_ATTRIBUTE_CONST get_buf_ptr(VALUE ign) { return g_buf_ptr; }
+static void init_buf(void)
+{
+        g_buf = rb_str_new(0, buf_capa - 1);
+        g_buf_ptr = RSTRING_PTR(g_buf);
+        rb_global_variable(&g_buf);
+}
+#else /* !UH_HAVE_GVL */
+static VALUE buf_key;
+static VALUE get_buf(void)
+{
+        VALUE buf = rb_thread_local_aref(rb_thread_current(), buf_key);
+
+        /*
+         * we must validate this, otherwise some bad code could muck
+         * with local vars in Thread.current and crash us
+         */
+        if (TYPE(buf) != T_STRING) {
+                buf = rb_str_new(0, buf_capa - 1);
+                rb_thread_local_aset(rb_thread_current(), buf_key, buf);
+        } else if (RSTRING_LEN(buf) != (long)buf_capa) {
+                rb_str_modify(buf);
+                rb_str_resize(buf, buf_capa - 1);
+        }
+
+        return buf;
+}
+
+static char *get_buf_ptr(VALUE buf) { return RSTRING_PTR(buf); }
+
+static void init_buf(void)
+{
+        buf_key = ID2SYM(rb_intern("uh_httpdate_buf"));
+        rb_global_variable(&buf_key); /* in case symbols ever get GC-ed */
+}
+#endif /* !UH_HAVE_GVL */
 
 /*
  * Returns a string which represents the time as rfc1123-date of HTTP-date
@@ -34,24 +86,20 @@ static struct tm * my_gmtime_r(time_t *now, struct tm *tm)
  * except it is implemented in C for performance.  We always saw
  * Time#httpdate at or near the top of the profiler output so we
  * decided to rewrite this in C.
- *
- * Caveats: it relies on a Ruby implementation with the global VM lock,
- * a thread-safe version will be provided when a Unix-only, GVL-free Ruby
- * implementation becomes viable.
  */
 static VALUE httpdate(VALUE self)
 {
         static time_t last;
         time_t now = time(NULL); /* not a syscall on modern 64-bit systems */
         struct tm tm;
+        VALUE buf = get_buf();
 
         if (last == now)
                 return buf;
         last = now;
         gmtime_r(&now, &tm);
 
-        /* we can make this thread-safe later if our Ruby loses the GVL */
-        snprintf(buf_ptr, buf_capa,
+        snprintf(get_buf_ptr(buf), buf_capa,
                  "%s, %02d %s %4d %02d:%02d:%02d GMT",
                  week + (tm.tm_wday * 4),
                  tm.tm_mday,
@@ -68,10 +116,13 @@ void init_unicorn_httpdate(void)
 {
         VALUE mod = rb_const_get(rb_cObject, rb_intern("Unicorn"));
         mod = rb_define_module_under(mod, "HttpResponse");
+        init_buf();
 
-        buf = rb_str_new(0, buf_capa - 1);
-        rb_global_variable(&buf);
-        buf_ptr = RSTRING_PTR(buf);
+        /*
+         * initialize, gmtime_r uses a lot of stack on FreeBSD for
+         * loading tzinfo data, so this allows a Ruby implementation
+         * to use * smaller thread stacks in child threads.
+         */
         httpdate(Qnil);
 
         rb_define_method(mod, "httpdate", httpdate, 0);