added replacements for atomic instructions on systems that do not support them.

[backport of Stefen Sledz' patch for v5]

5 files changed, 138 insertions, 0 deletions

diff --git a/ChangeLog b/ChangeLog
index dc12e856..b8deeb74 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -2,6 +2,8 @@
 Version 4.6.2  [v4-stable] (rgerhards), 2010-03-??
 - new feature: "." action type added to support writing files to relative
   pathes (this is primarily meant as a debug aid)
+- added replacements for atomic instructions on systems that do not
+  support them. [backport of Stefen Sledz' patch for v5)
 - added new property replacer option "date-rfc3164-buggyday" primarily
   to ease migration from syslog-ng. See property replacer doc for
   details. [backport from 5.5.3 because urgently needed by some]
diff --git a/configure.ac b/configure.ac
index b059fe75..fcd70c30 100644
--- a/configure.ac
+++ b/configure.ac
@@ -84,6 +84,7 @@ AC_TYPE_UINT8_T
 AC_HEADER_TIME
 AC_STRUCT_TM
 AC_C_VOLATILE
+AC_C_TYPEOF
 
 sa_includes="\
 $ac_includes_default
@@ -126,6 +127,9 @@ AC_TRY_COMPILE([
 # check for availability of atomic operations
 RS_ATOMIC_OPERATIONS
 
+# fall back to POSIX sems for atomic operations (cpu expensive)
+AC_CHECK_HEADERS([semaphore.h])
+
 
 # Additional module directories
 AC_ARG_WITH(moddirs,
diff --git a/runtime/Makefile.am b/runtime/Makefile.am
index 14abe722..e5b3ccdf 100644
--- a/runtime/Makefile.am
+++ b/runtime/Makefile.am
@@ -9,6 +9,7 @@ librsyslog_la_SOURCES = \
 	rsyslog.h \
 	unicode-helper.h \
 	atomic.h \
+	atomic-posix-sem.c \
 	syslogd-types.h \
 	module-template.h \
 	obj-types.h \
diff --git a/runtime/atomic.h b/runtime/atomic.h
index 62ceb8b3..ea3be37a 100644
--- a/runtime/atomic.h
+++ b/runtime/atomic.h
@@ -53,6 +53,122 @@
 #	define ATOMIC_CAS(data, oldVal, newVal) __sync_bool_compare_and_swap(&(data), (oldVal), (newVal));
 #	define ATOMIC_CAS_VAL(data, oldVal, newVal) __sync_val_compare_and_swap(&(data), (oldVal), (newVal));
 #else
+#ifdef HAVE_SEMAPHORE_H
+	/* we use POSIX semaphores instead */
+
+#include "rsyslog.h"
+#include <semaphore.h>
+
+extern sem_t atomicSem;
+rsRetVal atomicSemInit(void);
+void atomicSemExit(void);
+
+#if HAVE_TYPEOF
+#define my_typeof(x) typeof(x)
+#else /* sorry, can't determine types, using 'int' */
+#define my_typeof(x) int
+#endif
+
+#	define ATOMIC_SUB(data, val) \
+({ \
+	my_typeof(data) tmp; \
+	sem_wait(&atomicSem); \
+	tmp = data; \
+	data -= val; \
+	sem_post(&atomicSem); \
+	tmp; \
+})
+
+#	define ATOMIC_ADD(data, val) \
+({ \
+	my_typeof(data) tmp; \
+	sem_wait(&atomicSem); \
+	tmp = data; \
+	data += val; \
+	sem_post(&atomicSem); \
+	tmp; \
+})
+
+#	define ATOMIC_INC_AND_FETCH(data) \
+({ \
+	my_typeof(data) tmp; \
+	sem_wait(&atomicSem); \
+	tmp = data; \
+	data += 1; \
+	sem_post(&atomicSem); \
+	tmp; \
+})
+
+#	define ATOMIC_INC(data) ((void) ATOMIC_INC_AND_FETCH(data))
+
+#	define ATOMIC_DEC_AND_FETCH(data) \
+({ \
+	sem_wait(&atomicSem); \
+	data -= 1; \
+	sem_post(&atomicSem); \
+	data; \
+})
+
+#	define ATOMIC_DEC(data) ((void) ATOMIC_DEC_AND_FETCH(data))
+
+#	define ATOMIC_FETCH_32BIT(data) ((unsigned) ATOMIC_ADD((data), 0xffffffff))
+
+#	define ATOMIC_STORE_1_TO_32BIT(data) \
+({ \
+	my_typeof(data) tmp; \
+	sem_wait(&atomicSem); \
+	tmp = data; \
+	data = 1; \
+	sem_post(&atomicSem); \
+	tmp; \
+})
+
+#	define ATOMIC_STORE_0_TO_INT(data) \
+({ \
+	my_typeof(data) tmp; \
+	sem_wait(&atomicSem); \
+	tmp = data; \
+	data = 0; \
+	sem_post(&atomicSem); \
+	tmp; \
+})
+
+#	define ATOMIC_STORE_1_TO_INT(data) \
+({ \
+	my_typeof(data) tmp; \
+	sem_wait(&atomicSem); \
+	tmp = data; \
+	data = 1; \
+	sem_post(&atomicSem); \
+	tmp; \
+})
+
+#	define ATOMIC_CAS(data, oldVal, newVal) \
+({ \
+	int ret; \
+	sem_wait(&atomicSem); \
+	if(data != oldVal) ret = 0; \
+	else \
+	{ \
+		data = newVal; \
+		ret = 1; \
+	} \
+	sem_post(&atomicSem); \
+	ret; \
+})
+
+#	define ATOMIC_CAS_VAL(data, oldVal, newVal) \
+({ \
+	sem_wait(&atomicSem); \
+	if(data == oldVal) \
+	{ \
+		data = newVal; \
+	} \
+	sem_post(&atomicSem); \
+	data; \
+})
+
+#else /* not HAVE_SEMAPHORE_H */
 	/* note that we gained parctical proof that theoretical problems DO occur
 	 * if we do not properly address them. See this blog post for details:
 	 * http://blog.gerhards.net/2009/01/rsyslog-data-race-analysis.html
@@ -70,5 +186,6 @@
 #	define ATOMIC_STORE_0_TO_INT(data) (data) = 0
 #	define ATOMIC_CAS_VAL(data, oldVal, newVal) (data) = (newVal)
 #endif
+#endif
 
 #endif /* #ifndef INCLUDED_ATOMIC_H */
diff --git a/runtime/rsyslog.c b/runtime/rsyslog.c
index 443d0f41..5750ca76 100644
--- a/runtime/rsyslog.c
+++ b/runtime/rsyslog.c
@@ -80,6 +80,7 @@
 #include "prop.h"
 #include "rule.h"
 #include "ruleset.h"
+#include "atomic.h"
 
 /* forward definitions */
 static rsRetVal dfltErrLogger(int, uchar *errMsg);
@@ -139,6 +140,12 @@ rsrtInit(char **ppErrObj, obj_if_t *pObjIF)
 		CHKiRet(objClassInit(NULL)); /* *THIS* *MUST* always be the first class initilizer being called! */
 		CHKiRet(objGetObjInterface(pObjIF)); /* this provides the root pointer for all other queries */
 
+#ifndef HAVE_ATOMIC_BUILTINS
+#ifdef HAVE_SEMAPHORE_H
+		CHKiRet(atomicSemInit());
+#endif /* HAVE_SEMAPHORE_H */
+#endif /* !defined(HAVE_ATOMIC_BUILTINS) */
+
 		/* initialize core classes. We must be very careful with the order of events. Some
 		 * classes use others and if we do not initialize them in the right order, we may end
 		 * up with an invalid call. The most important thing that can happen is that an error
@@ -215,6 +222,13 @@ rsrtExit(void)
 		glblClassExit();
 		rulesetClassExit();
 		ruleClassExit();
+
+#ifndef HAVE_ATOMIC_BUILTINS
+#ifdef HAVE_SEMAPHORE_H
+		atomicSemExit();
+#endif /* HAVE_SEMAPHORE_H */
+#endif /* !defined(HAVE_ATOMIC_BUILTINS) */
+
 		objClassExit(); /* *THIS* *MUST/SHOULD?* always be the first class initilizer being called (except debug)! */
 	}