2320. [func] Make statistics couters thread-safe for platforms

			that support certain atomic operations. [RT #17466]

CHANGES

+2320.	[func]		Make statistics couters thread-safe for platforms
+			that support certain atomic operations. [RT #17466]
+
 2319.	[bug]		Silence Coverity warnings in 
 			lib/dns/rdata/in_1/apl_42.c. [RT #17469]
 

bin/named/include/named/server.h

@@ -15,7 +15,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: server.h,v 1.91 2008/01/18 23:46:57 tbox Exp $ */
+/* $Id: server.h,v 1.92 2008/01/24 02:00:44 jinmei Exp $ */
 
 #ifndef NAMED_SERVER_H
 #define NAMED_SERVER_H 1
@@ -91,7 +91,7 @@ struct ns_server {
 	isc_boolean_t		flushonshutdown;
 	isc_boolean_t		log_queries;	/*%< For BIND 8 compatibility */
 
-	isc_uint64_t *		querystats;	/*%< Query statistics counters */
+	dns_stats_t *		querystats;	/*%< Query statistics counters */
 
 	ns_controls_t *		controls;	/*%< Control channels */
 	unsigned int		dispatchgen;

bin/named/query.c

@@ -15,7 +15,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: query.c,v 1.302 2008/01/18 23:46:57 tbox Exp $ */
+/* $Id: query.c,v 1.303 2008/01/24 02:00:43 jinmei Exp $ */
 
 /*! \file */
 
@@ -130,12 +130,12 @@ inc_stats(ns_client_t *client, dns_statscounter_t counter) {
 
 	REQUIRE(counter < DNS_STATS_NCOUNTERS);
 
-	ns_g_server->querystats[counter]++;
+	dns_stats_incrementcounter(ns_g_server->querystats, counter);
 
 	if (zone != NULL) {
-		isc_uint64_t *zonestats = dns_zone_getstatscounters(zone);
+		dns_stats_t *zonestats = dns_zone_getstats(zone);
 		if (zonestats != NULL)
-			zonestats[counter]++;
+			dns_stats_incrementcounter(zonestats, counter);
 	}
 }
 

bin/named/server.c

@@ -15,7 +15,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: server.c,v 1.500 2008/01/22 00:29:03 jinmei Exp $ */
+/* $Id: server.c,v 1.501 2008/01/24 02:00:44 jinmei Exp $ */
 
 /*! \file */
 
@@ -3800,8 +3800,8 @@ ns_server_create(isc_mem_t *mctx, ns_server_t **serverp) {
 	server->server_usehostname = ISC_FALSE;
 	server->server_id = NULL;
 
-	CHECKFATAL(dns_stats_alloccounters(ns_g_mctx, &server->querystats),
-		   "dns_stats_alloccounters");
+	CHECKFATAL(dns_stats_create(ns_g_mctx, &server->querystats),
+		   "dns_stats_create");
 
 	server->flushonshutdown = ISC_FALSE;
 	server->log_queries = ISC_FALSE;
@@ -3825,7 +3825,7 @@ ns_server_destroy(ns_server_t **serverp) {
 
 	ns_controls_destroy(&server->controls);
 
-	dns_stats_freecounters(server->mctx, &server->querystats);
+	dns_stats_destroy(server->mctx, &server->querystats);
 
 	isc_mem_free(server->mctx, server->statsfile);
 	isc_mem_free(server->mctx, server->dumpfile);
@@ -4394,6 +4394,7 @@ ns_server_dumpstats(ns_server_t *server) {
 	FILE *fp = NULL;
 	int i;
 	int ncounters;
+	isc_uint64_t counters[DNS_STATS_NCOUNTERS];
 
 	isc_stdtime_get(&now);
 
@@ -4403,22 +4404,23 @@ ns_server_dumpstats(ns_server_t *server) {
 	ncounters = DNS_STATS_NCOUNTERS;
 	fprintf(fp, "+++ Statistics Dump +++ (%lu)\n", (unsigned long)now);
 
+	dns_stats_copy(server->querystats, counters);
 	for (i = 0; i < ncounters; i++)
 		fprintf(fp, "%s %" ISC_PRINT_QUADFORMAT "u\n",
-			dns_statscounter_names[i],
-			server->querystats[i]);
+			dns_statscounter_names[i], counters[i]);
 
 	zone = NULL;
 	for (result = dns_zone_first(server->zonemgr, &zone);
 	     result == ISC_R_SUCCESS;
 	     next = NULL, result = dns_zone_next(zone, &next), zone = next)
 	{
-		isc_uint64_t *zonestats = dns_zone_getstatscounters(zone);
+		dns_stats_t *zonestats = dns_zone_getstats(zone);
 		if (zonestats != NULL) {
 			char zonename[DNS_NAME_FORMATSIZE];
 			dns_view_t *view;
 			char *viewname;
 
+			dns_stats_copy(zonestats, counters);
 			dns_name_format(dns_zone_getorigin(zone),
 					zonename, sizeof(zonename));
 			view = dns_zone_getview(zone);
@@ -4427,7 +4429,7 @@ ns_server_dumpstats(ns_server_t *server) {
 				fprintf(fp, "%s %" ISC_PRINT_QUADFORMAT
 					"u %s",
 					dns_statscounter_names[i],
-					zonestats[i],
+					counters[i],
 					zonename);
 				if (strcmp(viewname, "_default") != 0)
 					fprintf(fp, " %s", viewname);

bin/named/statschannel.c

@@ -14,7 +14,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: statschannel.c,v 1.4 2008/01/18 23:46:57 tbox Exp $ */
+/* $Id: statschannel.c,v 1.5 2008/01/24 02:00:44 jinmei Exp $ */
 
 /*! \file */
 
@@ -71,6 +71,7 @@ generatexml(ns_server_t *server, int *buflen, xmlChar **buf) {
 	int xmlrc;
 	dns_view_t *view;
 	int i;
+	isc_uint64_t counters[DNS_STATS_NCOUNTERS];
 
 	isc_time_now(&now);
 	isc_time_formatISO8601(&ns_g_boottime, boottime, sizeof boottime);
@@ -117,12 +118,13 @@ generatexml(ns_server_t *server, int *buflen, xmlChar **buf) {
 	xmlTextWriterWriteString(writer, ISC_XMLCHAR nowstr);
 	xmlTextWriterEndElement(writer);
 	TRY0(xmlTextWriterStartElement(writer, ISC_XMLCHAR "counters"));
+	dns_stats_copy(server->querystats, counters);
 	for (i = 0; i < DNS_STATS_NCOUNTERS; i++) {
 		xmlTextWriterStartElement(writer,
 					ISC_XMLCHAR dns_statscounter_names[i]);
 		xmlTextWriterWriteFormatString(writer,
 					       "%" ISC_PRINT_QUADFORMAT "u",
-					       server->querystats[i]);
+					       counters[i]);
 		xmlTextWriterEndElement(writer);
 	}
 	xmlTextWriterEndElement(writer); /* counters */

configure.in

@@ -18,7 +18,7 @@ AC_DIVERT_PUSH(1)dnl
 esyscmd([sed "s/^/# /" COPYRIGHT])dnl
 AC_DIVERT_POP()dnl
 
-AC_REVISION($Revision: 1.436 $)
+AC_REVISION($Revision: 1.437 $)
 
 AC_INIT(lib/dns/name.c)
 AC_PREREQ(2.59)
@@ -2123,11 +2123,13 @@ main() {
 	exit((sizeof(void *) == 8) ? 0 : 1);
 }
 ],
-		[arch=x86_64],
+		[arch=x86_64
+		have_xaddq=yes],
 		[arch=x86_32],
 		[arch=x86_32])
 	;;
 	x86_64-*)
+		have_xaddq=yes
 		arch=x86_64
 	;;
 	alpha*-*)
@@ -2232,7 +2234,14 @@ else
 	ISC_PLATFORM_HAVEATOMICSTORE="#undef ISC_PLATFORM_HAVEATOMICSTORE"
 fi
 
+if test "$have_xaddq" = "yes"; then
+        ISC_PLATFORM_HAVEXADDQ="#define ISC_PLATFORM_HAVEXADDQ 1"
+else
+        ISC_PLATFORM_HAVEXADDQ="#undef ISC_PLATFORM_HAVEXADDQ"
+fi
+
 AC_SUBST(ISC_PLATFORM_HAVEXADD)
+AC_SUBST(ISC_PLATFORM_HAVEXADDQ)
 AC_SUBST(ISC_PLATFORM_HAVECMPXCHG)
 AC_SUBST(ISC_PLATFORM_HAVEATOMICSTORE)
 

lib/dns/include/dns/stats.h

@@ -15,7 +15,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: stats.h,v 1.13 2007/06/19 23:47:17 tbox Exp $ */
+/* $Id: stats.h,v 1.14 2008/01/24 02:00:44 jinmei Exp $ */
 
 #ifndef DNS_STATS_H
 #define DNS_STATS_H 1
@@ -42,11 +42,66 @@ typedef enum {
 
 LIBDNS_EXTERNAL_DATA extern const char *dns_statscounter_names[];
 
+isc_result_t
+dns_stats_create(isc_mem_t *mctx, dns_stats_t **statsp);
+/*%<
+ * Create a statistics counter structure.
+ *
+ * Requires:
+ *
+ *\li	'mctx' must be a valid memory context.
+ *
+ *\li	'statsp' != NULL && '*statsp' == NULL.
+ */
+
+void
+dns_stats_destroy(isc_mem_t *mctx, dns_stats_t **statsp);
+/*%<
+ * Destroy a statistics counter structure.
+ *
+ * Requires:
+ *
+ *\li	'mctx' must be a valid memory context.
+ *
+ *\li	'statsp' != NULL and '*statsp' be valid dns_stats_t.
+ *
+ * Ensures:
+ *
+ *\li	'*statsp' == NULL
+ */
+
+void
+dns_stats_incrementcounter(dns_stats_t *stat, dns_statscounter_t counter);
+/*%<
+ * Increment a counter field of 'stat' specified by 'counter'.
+ *
+ * Requires:
+ *
+ *\li	'stat' be a valid dns_stats_t.
+ *
+ *\li	counter < DNS_STATS_NCOUNTERS
+ */
+
+void
+dns_stats_copy(dns_stats_t *src, isc_uint64_t *dst);
+/*%<
+ * Copy statistics counter fields of 'src' to the 'dst' array.
+ *
+ * Requires:
+ *
+ *\li	'src' be a valid dns_stats_t.
+ *
+ *\li	'dst' be sufficiently large to store DNS_STATS_NCOUNTERS 64-bit
+ *	integers.
+ */
+
 isc_result_t
 dns_stats_alloccounters(isc_mem_t *mctx, isc_uint64_t **ctrp);
 /*%<
  * Allocate an array of query statistics counters from the memory
  * context 'mctx'.
+ *
+ * This function is obsoleted.  Use dns_stats_create() instead.
  */
 
 void
@@ -54,6 +109,8 @@ dns_stats_freecounters(isc_mem_t *mctx, isc_uint64_t **ctrp);
 /*%<
  * Free an array of query statistics counters allocated from the memory
  * context 'mctx'.
+ *
+ * This function is obsoleted.  Use dns_stats_destroy() instead.
  */
 
 ISC_LANG_ENDDECLS

lib/dns/include/dns/types.h

@@ -15,7 +15,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: types.h,v 1.126 2007/09/12 01:09:08 each Exp $ */
+/* $Id: types.h,v 1.127 2008/01/24 02:00:44 jinmei Exp $ */
 
 #ifndef DNS_TYPES_H
 #define DNS_TYPES_H 1
@@ -106,6 +106,7 @@ typedef isc_uint8_t				dns_secproto_t;
 typedef struct dns_signature			dns_signature_t;
 typedef struct dns_ssurule			dns_ssurule_t;
 typedef struct dns_ssutable			dns_ssutable_t;
+typedef struct dns_stats			dns_stats_t;
 typedef struct dns_tkeyctx			dns_tkeyctx_t;
 typedef isc_uint16_t				dns_trust_t;
 typedef struct dns_tsig_keyring			dns_tsig_keyring_t;

lib/dns/include/dns/zone.h

@@ -15,7 +15,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: zone.h,v 1.153 2007/09/18 00:22:31 marka Exp $ */
+/* $Id: zone.h,v 1.154 2008/01/24 02:00:44 jinmei Exp $ */
 
 #ifndef DNS_ZONE_H
 #define DNS_ZONE_H 1
@@ -1488,6 +1488,12 @@ dns_zone_setstatistics(dns_zone_t *zone, isc_boolean_t on);
 
 isc_uint64_t *
 dns_zone_getstatscounters(dns_zone_t *zone);
+/*%<
+ * This function is obsoleted by dns_zone_getstats().
+ */
+
+dns_stats_t *
+dns_zone_getstats(dns_zone_t *zone);
 /*%<
  * Requires:
  *      zone be a valid zone.

lib/dns/stats.c

@@ -15,13 +15,19 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: stats.c,v 1.12 2007/06/19 23:47:16 tbox Exp $ */
+/* $Id: stats.c,v 1.13 2008/01/24 02:00:44 jinmei Exp $ */
 
 /*! \file */
 
 #include <config.h>
 
+#include <string.h>
+
+#include <isc/atomic.h>
 #include <isc/mem.h>
+#include <isc/platform.h>
+#include <isc/rwlock.h>
+#include <isc/util.h>
 
 #include <dns/stats.h>
 
@@ -37,6 +43,143 @@ LIBDNS_EXTERNAL_DATA const char *dns_statscounter_names[DNS_STATS_NCOUNTERS] =
 	"dropped"
 	};
 
+#ifndef DNS_STATS_USEMULTIFIELDS
+#if defined(ISC_RWLOCK_USEATOMIC) && defined(ISC_PLATFORM_HAVEXADD) && !defined(ISC_PLATFORM_HAVEXADDQ)
+#define DNS_STATS_USEMULTIFIELDS 1
+#else
+#define DNS_STATS_USEMULTIFIELDS 0
+#endif
+#endif	/* DNS_STATS_USEMULTIFIELDS */
+
+#if DNS_STATS_USEMULTIFIELDS
+typedef struct {
+	isc_uint32_t hi;
+	isc_uint32_t lo;
+} dns_stat_t;
+#else
+typedef isc_uint64_t dns_stat_t;
+#endif
+
+struct dns_stats {
+	/* XXXJT: do we need a magic? */
+#ifdef ISC_RWLOCK_USEATOMIC
+	isc_rwlock_t	lock;
+#endif
+	dns_stat_t	counters[DNS_STATS_NCOUNTERS];
+};
+
+isc_result_t
+dns_stats_create(isc_mem_t *mctx, dns_stats_t **statsp) {
+	dns_stats_t *stats;
+	isc_result_t result = ISC_R_SUCCESS;
+
+	REQUIRE(statsp != NULL && *statsp == NULL);
+
+	stats = isc_mem_get(mctx, sizeof(*stats));
+	if (stats == NULL)
+		return (ISC_R_NOMEMORY);
+
+#ifdef ISC_RWLOCK_USEATOMIC
+	result = isc_rwlock_init(&stats->lock, 0, 0);
+	if (result != ISC_R_SUCCESS) {
+		isc_mem_put(mctx, stats, sizeof(*stats));
+		return (result);
+	}
+#endif
+
+	memset(stats->counters, 0, sizeof(dns_stat_t) * DNS_STATS_NCOUNTERS);
+
+	*statsp = stats;
+
+	return (result);
+}
+
+void
+dns_stats_destroy(isc_mem_t *mctx, dns_stats_t **statsp) {
+	dns_stats_t *stats;
+
+	REQUIRE(statsp != NULL && *statsp != NULL);
+
+	stats = *statsp;
+
+#ifdef ISC_RWLOCK_USEATOMIC
+	isc_rwlock_destroy(&stats->lock);
+#endif
+	isc_mem_put(mctx, stats, sizeof(*stats));
+
+	*statsp = NULL;
+}
+
+void
+dns_stats_incrementcounter(dns_stats_t *stats, dns_statscounter_t counter) {
+	isc_int32_t prev;
+
+	REQUIRE(counter < DNS_STATS_NCOUNTERS);
+
+#ifdef ISC_RWLOCK_USEATOMIC
+	/*
+	 * We use a "read" lock to prevent other threads from reading the
+	 * counter while we "writing" a counter field.  The write access itself
+	 * is protected by the atomic operation.
+	 */
+	isc_rwlock_lock(&stats->lock, isc_rwlocktype_read);
+#endif
+
+#if DNS_STATS_USEMULTIFIELDS
+	prev = isc_atomic_xadd((isc_int32_t *)&stats->counters[counter].lo, 1);
+	/*
+	 * If the lower 32-bit field overflows, increment the higher field.
+	 * Note that it's *theoretically* possible that the lower field
+	 * overlaps again before the higher field is incremented.  It doesn't
+	 * matter, however, because we don't read the value until
+	 * dns_stats_copy() is called where the whole process is protected
+	 * by the write (exclusive) lock.
+	 */
+	if (prev == (isc_int32_t)0xffffffff)
+		isc_atomic_xadd((isc_int32_t *)&stats->counters[counter].hi, 1);
+#elif defined(ISC_PLATFORM_HAVEXADDQ)
+	UNUSED(prev);
+	isc_atomic_xaddq((isc_int64_t *)&stats->counters[counter], 1);
+#else
+	UNUSED(prev);
+	stats->counters[counter]++;
+#endif
+
+#ifdef ISC_RWLOCK_USEATOMIC
+	isc_rwlock_unlock(&stats->lock, isc_rwlocktype_read);
+#endif
+}
+
+void
+dns_stats_copy(dns_stats_t *src, isc_uint64_t *dst) {
+	int i;
+
+#ifdef ISC_RWLOCK_USEATOMIC
+	/*
+	 * We use a "write" lock before "reading" the statistics counters as
+	 * an exclusive lock.
+	 */
+	isc_rwlock_lock(&src->lock, isc_rwlocktype_write);
+#endif
+
+#if DNS_STATS_USEMULTIFIELDS
+	for (i = 0; i < DNS_STATS_NCOUNTERS; i++) {
+		dst[i] = ((isc_uint64_t)src->counters[i].hi) << 32 |
+			src->counters[i].lo;
+	}
+#else
+	UNUSED(i);
+	memcpy(dst, src->counters, DNS_STATS_NCOUNTERS * sizeof(dst[0]));
+#endif
+
+#ifdef ISC_RWLOCK_USEATOMIC
+	isc_rwlock_unlock(&src->lock, isc_rwlocktype_write);
+#endif
+}
+
+/***
+ *** Obsolete functions follow
+ ***/
 isc_result_t
 dns_stats_alloccounters(isc_mem_t *mctx, isc_uint64_t **ctrp) {
 	int i;

lib/dns/zone.c

@@ -15,7 +15,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: zone.c,v 1.470 2007/12/02 22:27:54 marka Exp $ */
+/* $Id: zone.c,v 1.471 2008/01/24 02:00:44 jinmei Exp $ */
 
 /*! \file */
 
@@ -251,7 +251,7 @@ struct dns_zone {
 	/*%
 	 * Optional per-zone statistics counters (NULL if not present).
 	 */
-	isc_uint64_t	    	*counters;
+	dns_stats_t	    	*counters;
 	isc_uint32_t		notifydelay;
 	dns_isselffunc_t	isself;
 	void			*isselfarg;
@@ -736,7 +736,7 @@ zone_free(dns_zone_t *zone) {
 		isc_mem_free(zone->mctx, zone->journal);
 	zone->journal = NULL;
 	if (zone->counters != NULL)
-		dns_stats_freecounters(zone->mctx, &zone->counters);
+		dns_stats_destroy(zone->mctx, &zone->counters);
 	if (zone->db != NULL)
 		zone_detachdb(zone);
 	if (zone->acache != NULL)
@@ -8092,11 +8092,11 @@ dns_zone_setstatistics(dns_zone_t *zone, isc_boolean_t on) {
 	if (on) {
 		if (zone->counters != NULL)
 			goto done;
-		result = dns_stats_alloccounters(zone->mctx, &zone->counters);
+		result = dns_stats_create(zone->mctx, &zone->counters);
 	} else {
 		if (zone->counters == NULL)
 			goto done;
-		dns_stats_freecounters(zone->mctx, &zone->counters);
+		dns_stats_destroy(zone->mctx, &zone->counters);
 	}
  done:
 	UNLOCK_ZONE(zone);
@@ -8105,6 +8105,15 @@ dns_zone_setstatistics(dns_zone_t *zone, isc_boolean_t on) {
 
 isc_uint64_t *
 dns_zone_getstatscounters(dns_zone_t *zone) {
+	/*
+	 * This function is obsoleted by dns_zone_getstats().
+	 */
+	UNUSED(zone);
+	return (NULL);
+}
+
+dns_stats_t *
+dns_zone_getstats(dns_zone_t *zone) {
 	return (zone->counters);
 }
 
@@ -8342,13 +8351,16 @@ dns_zone_xmlrender(dns_zone_t *zone, xmlTextWriterPtr xml, int flags)
 		xmlTextWriterEndElement(xml);
 
 		if (zone->counters != NULL) {
+			isc_uint64_t counters[DNS_STATS_NCOUNTERS];
+
 			xmlTextWriterStartElement(xml, ISC_XMLCHAR "counters");
+			dns_stats_copy(zone->counters, counters);
 			for (i = 0 ; i < DNS_STATS_NCOUNTERS ; i++) {
 				xmlTextWriterStartElement(xml,
 					ISC_XMLCHAR dns_statscounter_names[i]);
 				xmlTextWriterWriteFormatString(xml,
 					       "%" ISC_PRINT_QUADFORMAT "u",
-					       zone->counters[i]);
+					       counters[i]);
 				xmlTextWriterEndElement(xml);
 			}
 			xmlTextWriterEndElement(xml); /* counters */

lib/isc/include/isc/platform.h.in

@@ -15,7 +15,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: platform.h.in,v 1.45 2007/09/13 04:45:18 each Exp $ */
+/* $Id: platform.h.in,v 1.46 2008/01/24 02:00:44 jinmei Exp $ */
 
 #ifndef ISC_PLATFORM_H
 #define ISC_PLATFORM_H 1
@@ -236,6 +236,12 @@
  */
 @ISC_PLATFORM_HAVEXADD@
 
+/*
+ * If the "xaddq" operation (64bit xadd) is available on this architecture,
+ * ISC_PLATFORM_HAVEXADDQ will be defined. 
+ */
+@ISC_PLATFORM_HAVEXADDQ@
+
 /*
  * If the "atomic swap" operation is available on this architecture,
  * ISC_PLATFORM_HAVEATOMICSTORE" will be defined. 

lib/isc/x86_32/include/isc/atomic.h

@@ -14,7 +14,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: atomic.h,v 1.8 2007/07/27 14:22:53 explorer Exp $ */
+/* $Id: atomic.h,v 1.9 2008/01/24 02:00:44 jinmei Exp $ */
 
 #ifndef ISC_ATOMIC_H
 #define ISC_ATOMIC_H 1
@@ -43,6 +43,24 @@ isc_atomic_xadd(isc_int32_t *p, isc_int32_t val) {
 	return (prev);
 }
 
+#ifdef ISC_PLATFORM_HAVEXADDQ
+static __inline__ isc_int64_t
+isc_atomic_xaddq(isc_int64_t *p, isc_int64_t val) {
+	isc_int64_t prev = val;
+
+	__asm__ volatile(
+#ifdef ISC_PLATFORM_USETHREADS
+	    "lock;"
+#endif
+	    "xaddq %0, %1"
+	    :"=q"(prev)
+	    :"m"(*p), "0"(prev)
+	    :"memory", "cc");
+
+	return (prev);
+}
+#endif /* ISC_PLATFORM_HAVEXADDQ */
+
 /*
  * This routine atomically stores the value 'val' in 'p'.
  */

lib/isc/x86_64/include/isc/atomic.h

@@ -14,7 +14,7 @@
  * PERFORMANCE OF THIS SOFTWARE.
  */
 
-/* $Id: atomic.h,v 1.4 2007/06/19 23:47:21 tbox Exp $ */
+/* $Id: atomic.h,v 1.5 2008/01/24 02:00:44 jinmei Exp $ */
 
 #ifndef ISC_ATOMIC_H
 #define ISC_ATOMIC_H 1
@@ -49,15 +49,32 @@ isc_atomic_xadd(isc_int32_t *p, isc_int32_t val) {
 		"lock;"
 #endif
 		"xadd %eax, (%rdx)\n"
-
 		/*
-		 * set the return value directly in the register so that we
-		 * can avoid guessing the correct position in the stack for a
-		 * local variable.
+		 * XXX: assume %eax will be used as the return value.
 		 */
 		);
 }
 
+#ifdef ISC_PLATFORM_HAVEXADDQ
+static isc_int64_t
+isc_atomic_xaddq(isc_int64_t *p, isc_int64_t val) {
+        UNUSED(p);
+        UNUSED(val);