From 9293e823767daee79386cc797510808f4eed01a3 Mon Sep 17 00:00:00 2001 From: Lennart Poettering Date: Tue, 19 May 2009 22:30:14 +0200 Subject: atomic: implement atomic operations based on gcc's __sync extension Newer gccs and intel ccs support a __sync extension for making use of atomic operations. This patch replaces the handcrafted x86 atomic operation support with usage of __sync. __sync is supported by more processors and by more compilers than the old assembler code. Also, this extension has been available on gcc for quite a while now for x86, so replacing the old assembler code should only be a loss when very old compiilers are used. --- configure.in | 50 ++++++++++++++++-------------------------------- dbus/dbus-internals.h | 9 +++++++-- dbus/dbus-sysdeps-unix.c | 29 +++++----------------------- dbus/dbus-threads.c | 2 ++ 4 files changed, 30 insertions(+), 60 deletions(-) diff --git a/configure.in b/configure.in index b087b003..c2c6a8c9 100644 --- a/configure.in +++ b/configure.in @@ -590,41 +590,23 @@ if test "x$dbus_cv_va_val_copy" = "xno"; then fi -#### Atomic integers (checks by Sebastian Wilhelmi for GLib) -AC_MSG_CHECKING([whether to use inline assembler routines for atomic integers]) -have_atomic_inc_cond=0 -if test x"$GCC" = xyes; then - if test "x$enable_ansi" = "xyes"; then - AC_MSG_RESULT([no]) - else - case $host_cpu in - i386) - AC_MSG_RESULT([no]) - ;; - i?86) - case $host_os in - darwin*) - AC_MSG_RESULT([darwin]) - # check at compile-time, so that it is possible to build universal - # (with multiple architectures at once on the compile line) - have_atomic_inc_cond="(defined(__i386__) || defined(__x86_64__))" - ;; - *) - AC_MSG_RESULT([i486]) - have_atomic_inc_cond=1 - ;; - esac - ;; - *) - AC_MSG_RESULT([no]) - ;; - esac - fi +#### Atomic integers + +AC_CACHE_CHECK([whether $CC knows __sync_sub_and_fetch()], + dbus_cv_sync_sub_and_fetch, + [AC_LINK_IFELSE( + AC_LANG_PROGRAM([], [[int a = 4; __sync_sub_and_fetch(&a, 4);]]), + [dbus_cv_sync_sub_and_fetch=yes], + [dbus_cv_sync_sub_and_fetch=no]) + ]) + +if test "x$dbus_cv_sync_sub_and_fetch" = "xyes" ; then + have_sync=1 +else + have_sync=0 fi -AC_DEFINE_UNQUOTED([DBUS_USE_ATOMIC_INT_486_COND], [$have_atomic_inc_cond], - [Always defined; expands to 1 if we should use atomic integer implementation for 486, else 0]) -AC_DEFINE_UNQUOTED(DBUS_HAVE_ATOMIC_INT_COND, [$have_atomic_inc_cond], - [Always defined; expands to 1 if we have an atomic integer implementation, else 0]) + +AC_DEFINE_UNQUOTED([DBUS_USE_SYNC], [$have_sync], [Use the gcc __sync extension]) #### Various functions AC_CHECK_LIB(socket,socket) diff --git a/dbus/dbus-internals.h b/dbus/dbus-internals.h index 3e5f989d..835fe46a 100644 --- a/dbus/dbus-internals.h +++ b/dbus/dbus-internals.h @@ -294,18 +294,23 @@ _DBUS_DECLARE_GLOBAL_LOCK (pending_call_slots); _DBUS_DECLARE_GLOBAL_LOCK (server_slots); _DBUS_DECLARE_GLOBAL_LOCK (message_slots); /* 5-10 */ -_DBUS_DECLARE_GLOBAL_LOCK (atomic); _DBUS_DECLARE_GLOBAL_LOCK (bus); _DBUS_DECLARE_GLOBAL_LOCK (bus_datas); _DBUS_DECLARE_GLOBAL_LOCK (shutdown_funcs); _DBUS_DECLARE_GLOBAL_LOCK (system_users); -/* 10-15 */ _DBUS_DECLARE_GLOBAL_LOCK (message_cache); +/* 10-14 */ _DBUS_DECLARE_GLOBAL_LOCK (shared_connections); _DBUS_DECLARE_GLOBAL_LOCK (win_fds); _DBUS_DECLARE_GLOBAL_LOCK (sid_atom_cache); _DBUS_DECLARE_GLOBAL_LOCK (machine_uuid); + +#if !DBUS_USE_SYNC +_DBUS_DECLARE_GLOBAL_LOCK (atomic); #define _DBUS_N_GLOBAL_LOCKS (15) +#else +#define _DBUS_N_GLOBAL_LOCKS (14) +#endif dbus_bool_t _dbus_threads_init_debug (void); diff --git a/dbus/dbus-sysdeps-unix.c b/dbus/dbus-sysdeps-unix.c index 07db1c5f..42aa9674 100644 --- a/dbus/dbus-sysdeps-unix.c +++ b/dbus/dbus-sysdeps-unix.c @@ -2180,23 +2180,8 @@ _dbus_parse_uid (const DBusString *uid_str, return TRUE; } - +#if !DBUS_USE_SYNC _DBUS_DEFINE_GLOBAL_LOCK (atomic); - -#if DBUS_USE_ATOMIC_INT_486_COND -/* Taken from CVS version 1.7 of glibc's sysdeps/i386/i486/atomicity.h */ -/* Since the asm stuff here is gcc-specific we go ahead and use "inline" also */ -static inline dbus_int32_t -atomic_exchange_and_add (DBusAtomic *atomic, - volatile dbus_int32_t val) -{ - register dbus_int32_t result; - - __asm__ __volatile__ ("lock; xaddl %0,%1" - : "=r" (result), "=m" (atomic->value) - : "0" (val), "m" (atomic->value)); - return result; -} #endif /** @@ -2204,14 +2189,12 @@ atomic_exchange_and_add (DBusAtomic *atomic, * * @param atomic pointer to the integer to increment * @returns the value before incrementing - * - * @todo implement arch-specific faster atomic ops */ dbus_int32_t _dbus_atomic_inc (DBusAtomic *atomic) { -#if DBUS_USE_ATOMIC_INT_486_COND - return atomic_exchange_and_add (atomic, 1); +#if DBUS_USE_SYNC + return __sync_add_and_fetch(&atomic->value, 1)-1; #else dbus_int32_t res; _DBUS_LOCK (atomic); @@ -2227,14 +2210,12 @@ _dbus_atomic_inc (DBusAtomic *atomic) * * @param atomic pointer to the integer to decrement * @returns the value before decrementing - * - * @todo implement arch-specific faster atomic ops */ dbus_int32_t _dbus_atomic_dec (DBusAtomic *atomic) { -#if DBUS_USE_ATOMIC_INT_486_COND - return atomic_exchange_and_add (atomic, -1); +#if DBUS_USE_SYNC + return __sync_sub_and_fetch(&atomic->value, 1)+1; #else dbus_int32_t res; diff --git a/dbus/dbus-threads.c b/dbus/dbus-threads.c index 00c1a4b1..cb9c7237 100644 --- a/dbus/dbus-threads.c +++ b/dbus/dbus-threads.c @@ -424,7 +424,9 @@ init_locks (void) LOCK_ADDR (pending_call_slots), LOCK_ADDR (server_slots), LOCK_ADDR (message_slots), +#if !DBUS_USE_SYNC LOCK_ADDR (atomic), +#endif LOCK_ADDR (bus), LOCK_ADDR (bus_datas), LOCK_ADDR (shutdown_funcs), -- cgit