branches/zip:

Implement a check whether pthread_t objects can be used by GCC atomic
builtin functions. This check is implemented in plug.in and defines the
macro HAVE_ATOMIC_PTHREAD_T. This macro is checked in univ.i and the
relevant part of the code enabled (the one that uses GCC atomics against
pthread_t objects).

In addition to this, the same program that is compiled as part of the
plug.in check is added in ut/ut0auxconf.c. In the InnoDB Plugin source
archives that are shipped to the users, a generated Makefile.in is added.
That Makefile.in will be modified to compile ut/ut0auxconf.c and define
the macro HAVE_ATOMIC_PTHREAD_T if the compilation succeeds. I.e.
Makefile.in will emulate the work that is done by plug.in. This is done in
order to make the check happen and HAVE_ATOMIC_PTHREAD_T eventually
defined without regenerating MySQL's ./configure from
./storage/innobase/plug.in. The point is not to ask users to install the
autotools and regenerate ./configure.

rb://95

Approved by:	Marko

include/univ.i

@@ -116,10 +116,20 @@ of the 32-bit x86 assembler in mutex operations. */
 /* For InnoDB rw_locks to work with atomics we need the thread_id
 to be no more than machine word wide. The following enables using
 atomics for InnoDB rw_locks where these conditions are met. */
-# if defined(HAVE_GCC_ATOMIC_BUILTINS) && (defined(__linux__) \
-					   || defined(__FreeBSD__))
+#ifdef HAVE_GCC_ATOMIC_BUILTINS
+/* if HAVE_ATOMIC_PTHREAD_T is defined at this point that means that
+the code from plug.in has defined it and we do not need to include
+ut0auxconf.h which would either define HAVE_ATOMIC_PTHREAD_T or will
+be empty */
+# ifndef HAVE_ATOMIC_PTHREAD_T
+#  include "ut0auxconf.h"
+# endif /* HAVE_ATOMIC_PTHREAD_T */
+/* now HAVE_ATOMIC_PTHREAD_T is eventually defined either by plug.in or
+from Makefile.in->ut0auxconf.h */
+# ifdef HAVE_ATOMIC_PTHREAD_T
 #  define INNODB_RW_LOCKS_USE_ATOMICS
-# endif
+# endif /* HAVE_ATOMIC_PTHREAD_T */
+#endif /* HAVE_GCC_ATOMIC_BUILTINS */
 
 /* We only try to do explicit inlining of functions with gcc and
 Microsoft Visual C++ */

include/ut0auxconf.h

+/* Do not remove this file even though it is empty.
+This file is included in univ.i and will cause compilation failure
+if not present.
+A custom check has been added in the generated
+storage/innobase/Makefile.in that is shipped with with the InnoDB Plugin
+source archive. This check tries to compile a test program and if
+successful then adds "#define HAVE_ATOMIC_PTHREAD_T" to this file.
+This is a hack that has been developed in order to check for pthread_t
+atomicity without the need to regenerate the ./configure script that is
+distributed in the MySQL 5.1 official source archives.
+If by any chance Makefile.in and ./configure are regenerated and thus
+the hack from Makefile.in wiped away then the "real" check from plug.in
+will take over.
+*/

plug.in

@@ -51,6 +51,30 @@ MYSQL_PLUGIN_ACTIONS(innobase,  [
 		;;
   esac
   AC_SUBST(INNODB_DYNAMIC_CFLAGS)
+  AC_MSG_CHECKING(whether pthread_t can be used by GCC atomic builtins)
+  AC_TRY_RUN(
+    [
+      #include <pthread.h>
+
+      int main(int argc, char** argv) {
+        pthread_t       x1;
+        pthread_t       x2;
+        pthread_t       x3;
+
+        __sync_bool_compare_and_swap(&x1, x2, x3);
+
+        return(0);
+      }
+    ],
+    [
+      AC_DEFINE([HAVE_ATOMIC_PTHREAD_T], [1],
+                [pthread_t can be used by GCC atomic builtins])
+      AC_MSG_RESULT(yes)
+    ],
+    [
+      AC_MSG_RESULT(no)
+    ]
+    )
   ])
 
 # vim: set ft=config:

ut/ut0auxconf.c

+#include <pthread.h>
+
+int
+main(int argc, char** argv)
+{
+	pthread_t	x1;
+	pthread_t	x2;
+	pthread_t	x3;
+
+	__sync_bool_compare_and_swap(&x1, x2, x3);
+
+	return(0);
+}