Revision
82
Author
robert@fledge.watson.org
Date
2009-11-02 03:19:15 -0800 (Mon, 02 Nov 2009)

Log Message

Rework configure and conditional compilation logic for OS-provided
semaphores: generate USE_MACH_SEM and USE_POSIX_SEM definitions so that
precedence is selected in configure.ac rather than in the source code.
This makes the policy of "use Mach semaphores even if POSIX semaphoresare
available" explicit in the configuration process rather than implicit in
the ifdefs.

While here, migrate to defining a value of '1' rather than a simple
define, as suggested by Kevin Van Vechten.

In the future, we might want to add a --enable-posix-sem to allow forcing
the use of POSIX semaphores on Mac OS X.

Modified Paths

Diff

Modified: trunk/configure.ac (81 => 82)


--- trunk/configure.ac	2009-11-02 10:58:46 UTC (rev 81)
+++ trunk/configure.ac	2009-11-02 11:19:15 UTC (rev 82)
@@ -137,10 +137,10 @@
 #
 AC_CHECK_HEADER([mach/mach.h],
   [AC_DEFINE(HAVE_MACH,,Define if mach is present)
-    use_mig=true],
-  [use_mig=false]
+    have_mach=true],
+  [have_mach=false]
 )
-AM_CONDITIONAL(USE_MIG, $use_mig)
+AM_CONDITIONAL(USE_MIG, $have_mach)
 
 #
 # We use the availability of pthread_workqueue.h to decide whether to compile
@@ -160,8 +160,27 @@
 AC_CHECK_DECLS([FD_COPY], [], [], [[#include <sys/select.h>]])
 AC_CHECK_DECLS([SIGEMT], [], [], [[#include <signal.h>]])
 AC_CHECK_DECLS([VQ_UPDATE, VQ_VERYLOWDISK], [], [], [[#include <sys/mount.h>]])
-AC_CHECK_FUNCS([pthread_key_init_np pthread_main_np mach_absolute_time malloc_create_zone sem_init])
+AC_CHECK_FUNCS([pthread_key_init_np pthread_main_np mach_absolute_time malloc_create_zone])
 
+AC_CHECK_FUNC([sem_init],
+  [have_sem_init=true],
+  [have_sem_init=false]
+)
+
+#
+# We support both Mach semaphores and POSIX semaphores; if the former are
+# available, prefer them.
+#
+AC_MSG_CHECKING([what semaphore type to use]);
+AS_IF([test "x$have_mach" = "xtrue"],
+  [AC_DEFINE(USE_MACH_SEM,1,[Define to use Mach semaphores])
+    AC_MSG_RESULT([Mach semaphores])],
+  [test "x$have_sem_init" = "xtrue"],
+  [AC_DEFINE(USE_POSIX_SEM,1,[Define to use POSIX semaphores])
+    AC_MSG_RESULT([POSIX semaphores])],
+  [AC_MSG_ERROR([no supported semaphore type])]
+)
+
 AC_CHECK_HEADERS([sys/cdefs.h], [], [],
   [#ifdef HAVE_SYS_CDEFS_H
    #include <sys/cdefs.h>

Modified: trunk/src/internal.h (81 => 82)


--- trunk/src/internal.h	2009-11-02 10:58:46 UTC (rev 81)
+++ trunk/src/internal.h	2009-11-02 11:19:15 UTC (rev 82)
@@ -105,7 +105,7 @@
 #include <fcntl.h>
 #include <limits.h>
 #include <search.h>
-#if !defined(HAVE_MACH) && defined(HAVE_SEM_INIT)
+#if USE_POSIX_SEM
 #include <semaphore.h>
 #endif
 #include <signal.h>

Modified: trunk/src/legacy.h (81 => 82)


--- trunk/src/legacy.h	2009-11-02 10:58:46 UTC (rev 81)
+++ trunk/src/legacy.h	2009-11-02 11:19:15 UTC (rev 82)
@@ -51,9 +51,12 @@
 	struct dispatch_item_s *volatile        di_next;
 	dispatch_queue_t                        di_cback_q;
 	uint32_t                                di_flags;
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 	semaphore_t                             di_semaphore;
 #endif
+#if USE_POSIX_SEM
+	/* Legacy API not supported except with Mach semaphores. */
+#endif
 	void *					di_work_func;
 	void *                                  di_work_ctxt;
 	void *					di_cback_func;

Modified: trunk/src/queue.c (81 => 82)


--- trunk/src/queue.c	2009-11-02 10:58:46 UTC (rev 81)
+++ trunk/src/queue.c	2009-11-02 11:19:15 UTC (rev 82)
@@ -1110,9 +1110,10 @@
 	pthread_workqueue_attr_t pwq_attr;
 	int r;
 #endif
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 	kern_return_t kr;
-#else
+#endif
+#if USE_POSIX_SEM
 	int ret;
 #endif
 	int i;
@@ -1141,13 +1142,14 @@
 				dispatch_assume_zero(r);
 			}
 #endif /* HAVE_PTHREAD_WORKQUEUES */
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 			// override the default FIFO behavior for the pool semaphores
 			kr = semaphore_create(mach_task_self(), &_dispatch_thread_mediator[i].dsema_port, SYNC_POLICY_LIFO, 0);
 			DISPATCH_VERIFY_MIG(kr);
 			dispatch_assume_zero(kr);
 			dispatch_assume(_dispatch_thread_mediator[i].dsema_port);
-#else
+#endif
+#if USE_POSIX_SEM
 			/* XXXRW: POSIX semaphores don't support LIFO? */
 			ret = sem_init(&_dispatch_thread_mediator[i].dsema_sem, 0, 0);
 			dispatch_assume_zero(ret);

Modified: trunk/src/semaphore.c (81 => 82)


--- trunk/src/semaphore.c	2009-11-02 10:58:46 UTC (rev 81)
+++ trunk/src/semaphore.c	2009-11-02 11:19:15 UTC (rev 82)
@@ -21,13 +21,14 @@
 #include "internal.h"
 
 // semaphores are too fundamental to use the dispatch_assume*() macros
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 #define DISPATCH_SEMAPHORE_VERIFY_KR(x)	do {	\
 		if (x) {	\
 			DISPATCH_CRASH("flawed group/semaphore logic");	\
 		}	\
 	} while (0)
-#else
+#endif
+#if USE_POSIX_SEM
 #define	DISPATCH_SEMAPHORE_VERIFY_RET(x) do {				\
 		if ((x) == -1) {					\
 			DISPATCH_CRASH("flawed group/semaphore logic");	\
@@ -108,7 +109,7 @@
 	return dsema;
 }
 
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 static void
 _dispatch_semaphore_create_port(semaphore_t *s4)
 {
@@ -138,7 +139,8 @@
 
 	_dispatch_safe_fork = false;
 }
-#else /* !HAVE_MACH */
+#endif
+#if USE_POSIX_SEM
 static void
 _dispatch_posix_semaphore_create(sem_t *s4)
 {
@@ -151,16 +153,17 @@
 	ret = sem_init(s4, 0, 0);
 	dispatch_assume_zero(ret);
 }
-#endif /* HAVE_MACH */
+#endif
 
 DISPATCH_NOINLINE
 static long
 _dispatch_semaphore_wait_slow(dispatch_semaphore_t dsema, dispatch_time_t timeout)
 {
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 	mach_timespec_t _timeout;
 	kern_return_t kr;
-#else
+#endif
+#if USE_POSIX_SEM
 	struct timespec _timeout;
 	int ret;
 #endif
@@ -177,9 +180,10 @@
 		}
 	}
 
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 	_dispatch_semaphore_create_port(&dsema->dsema_port);
-#else
+#endif
+#if USE_POSIX_SEM
 	_dispatch_posix_semaphore_create(&dsema->dsema_sem);
 #endif
 
@@ -193,7 +197,7 @@
 
 	switch (timeout) {
 	default:
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 		do {
 			// timeout() already calculates relative time left
 			nsec = _dispatch_timeout(timeout);
@@ -206,7 +210,8 @@
 			DISPATCH_SEMAPHORE_VERIFY_KR(kr);
 			break;
 		}
-#else /* !HAVE_MACH */
+#endif
+#if USE_POSIX_SEM
 		do {
 			nsec = _dispatch_timeout(timeout);
 			_timeout.tv_sec = (typeof(_timeout.tv_sec))
@@ -221,14 +226,15 @@
 			DISPATCH_SEMAPHORE_VERIFY_RET(ret);
 			break;
 		}
-#endif /* HAVE_MACH */
+#endif
 		// Fall through and try to undo what the fast path did to dsema->dsema_value
 	case DISPATCH_TIME_NOW:
 		while ((orig = dsema->dsema_value) < 0) {
 			if (dispatch_atomic_cmpxchg(&dsema->dsema_value, orig, orig + 1)) {
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 				return KERN_OPERATION_TIMED_OUT;
-#else
+#endif
+#if USE_POSIX_SEM
 				errno = ETIMEDOUT;
 				return -1;
 #endif
@@ -237,12 +243,13 @@
 		// Another thread called semaphore_signal().
 		// Fall through and drain the wakeup.
 	case DISPATCH_TIME_FOREVER:
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 		do {
 			kr = semaphore_wait(dsema->dsema_port);
 		} while (kr == KERN_ABORTED);
 		DISPATCH_SEMAPHORE_VERIFY_KR(kr);
-#else
+#endif
+#if USE_POSIX_SEM
 		do {
 			ret = sem_wait(&dsema->dsema_sem);
 		} while (ret != 0);
@@ -318,9 +325,10 @@
 static long
 _dispatch_semaphore_signal_slow(dispatch_semaphore_t dsema)
 {
-#ifndef HAVE_MACH
+#if USE_POSIX_SEM
 	int ret;
-#else
+#endif
+#if USE_MACH_SEM
 	kern_return_t kr;
 	
 	_dispatch_semaphore_create_port(&dsema->dsema_port);
@@ -335,10 +343,11 @@
 	
 	dispatch_atomic_inc(&dsema->dsema_sent_ksignals);
 	
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 	kr = semaphore_signal(dsema->dsema_port);
 	DISPATCH_SEMAPHORE_VERIFY_KR(kr);
-#else
+#endif
+#if USE_POSIX_SEM
 	ret = sem_post(&dsema->dsema_sem);
 #endif
 
@@ -398,22 +407,24 @@
 	struct dispatch_sema_notify_s *tmp, *head = dispatch_atomic_xchg(&dsema->dsema_notify_head, NULL);
 	long rval = dispatch_atomic_xchg(&dsema->dsema_group_waiters, 0);
 	bool do_rel = head;
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 	long kr;
-#else
+#endif
+#if USE_POSIX_SEM
 	int ret;
 #endif
 
 	// wake any "group" waiter or notify blocks
 	
 	if (rval) {
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 		_dispatch_semaphore_create_port(&dsema->dsema_waiter_port);
 		do {
 			kr = semaphore_signal(dsema->dsema_waiter_port);
 			DISPATCH_SEMAPHORE_VERIFY_KR(kr);
 		} while (--rval);
-#else
+#endif
+#if USE_POSIX_SEM
 		do {
 			ret = sem_post(&dsema->dsema_sem);
 			DISPATCH_SEMAPHORE_VERIFY_RET(ret);
@@ -439,10 +450,11 @@
 static long
 _dispatch_group_wait_slow(dispatch_semaphore_t dsema, dispatch_time_t timeout)
 {
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 	mach_timespec_t _timeout;
 	kern_return_t kr;
-#else
+#endif
+#if USE_POSIX_SEM
 	struct timespec _timeout;
 	int ret;
 #endif
@@ -463,7 +475,7 @@
 		return _dispatch_group_wake(dsema);
 	}
 
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 	_dispatch_semaphore_create_port(&dsema->dsema_waiter_port);
 #endif
 	
@@ -477,7 +489,7 @@
 	
 	switch (timeout) {
 	default:
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 		do {
 			nsec = _dispatch_timeout(timeout);
 			_timeout.tv_sec = (typeof(_timeout.tv_sec))(nsec / NSEC_PER_SEC);
@@ -488,7 +500,8 @@
 			DISPATCH_SEMAPHORE_VERIFY_KR(kr);
 			break;
 		}
-#else
+#endif
+#if USE_POSIX_SEM
 		do {
 			nsec = _dispatch_timeout(timeout);
 			_timeout.tv_sec = (typeof(_timeout.tv_sec))
@@ -507,9 +520,10 @@
 	case DISPATCH_TIME_NOW:
 		while ((orig = dsema->dsema_group_waiters)) {
 			if (dispatch_atomic_cmpxchg(&dsema->dsema_group_waiters, orig, orig - 1)) {
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 				return KERN_OPERATION_TIMED_OUT;
-#else
+#endif
+#if USE_POSIX_SEM
 				errno = ETIMEDOUT;
 				return -1;
 #endif
@@ -518,12 +532,13 @@
 		// Another thread called semaphore_signal().
 		// Fall through and drain the wakeup.
 	case DISPATCH_TIME_FOREVER:
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 		do {
 			kr = semaphore_wait(dsema->dsema_waiter_port);
 		} while (kr == KERN_ABORTED);
 		DISPATCH_SEMAPHORE_VERIFY_KR(kr);
-#else
+#endif
+#if USE_POSIX_SEM
 		do {
 			ret = sem_wait(&dsema->dsema_sem);
 		} while (ret == -1 && errno == EINTR);
@@ -544,9 +559,10 @@
 		return 0;
 	}
 	if (timeout == 0) {
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 		return KERN_OPERATION_TIMED_OUT;
-#else
+#endif
+#if USE_POSIX_SEM
 		errno = ETIMEDOUT;
 		return (-1);
 #endif
@@ -594,9 +610,10 @@
 void
 _dispatch_semaphore_dispose(dispatch_semaphore_t dsema)
 {
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 	kern_return_t kr;
-#else
+#endif
+#if USE_POSIX_SEM
 	int ret;
 #endif
 	
@@ -604,7 +621,7 @@
 		DISPATCH_CLIENT_CRASH("Semaphore/group object deallocated while in use");
 	}
 	
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 	if (dsema->dsema_port) {
 		kr = semaphore_destroy(mach_task_self(), dsema->dsema_port);
 		DISPATCH_SEMAPHORE_VERIFY_KR(kr);
@@ -613,7 +630,8 @@
 		kr = semaphore_destroy(mach_task_self(), dsema->dsema_waiter_port);
 		DISPATCH_SEMAPHORE_VERIFY_KR(kr);
 	}
-#else
+#endif
+#if USE_POSIX_SEM
 	ret = sem_destroy(&dsema->dsema_sem);
 	DISPATCH_SEMAPHORE_VERIFY_RET(ret);
 #endif
@@ -627,7 +645,7 @@
 	size_t offset = 0;
 	offset += snprintf(&buf[offset], bufsiz - offset, "%s[%p] = { ", dx_kind(dsema), dsema);
 	offset += dispatch_object_debug_attr(dsema, &buf[offset], bufsiz - offset);
-#ifdef HAVE_MACH
+#if USE_MACH_SEM
 	offset += snprintf(&buf[offset], bufsiz - offset, "port = 0x%u, ",
 	    dsema->dsema_port);
 #endif

Modified: trunk/src/semaphore_internal.h (81 => 82)


--- trunk/src/semaphore_internal.h	2009-11-02 10:58:46 UTC (rev 81)
+++ trunk/src/semaphore_internal.h	2009-11-02 11:19:15 UTC (rev 82)
@@ -39,10 +39,12 @@
 	long dsema_value;
 	long dsema_orig;
 	size_t dsema_sent_ksignals;
-#ifdef HAVE_MACH
+#if USE_MACH_SEM && USE_POSIX_SEM
+#error "Too many supported semaphore types"
+#elif USE_MACH_SEM
 	semaphore_t dsema_port;
 	semaphore_t dsema_waiter_port;
-#elif defined(HAVE_SEM_INIT)
+#elif USE_POSIX_SEM
 	sem_t dsema_sem;
 #else
 #error "No supported semaphore type"