improved testbench / solved imdiag race condition

imdiag/imtcp had a modload race condition (as imdiag is a testing aid,
this has no implications for production deployments). Also, I replaced
netcat by a custom program to talk to imdiag. This, for the first time ever,
is now a Java program. I plan to add some GUI troubleshooting tools and
thought it is a good idea to start doing things in Java that can simply
be done in that language.

1 files changed, 21 insertions, 0 deletions

diff --git a/runtime/modules.c b/runtime/modules.c
index 9fdb48e7..3e8662a3 100644
--- a/runtime/modules.c
+++ b/runtime/modules.c
@@ -40,6 +40,7 @@
 #include <time.h>
 #include <assert.h>
 #include <errno.h>
+#include <pthread.h>
 #ifdef	OS_BSD
 #	include "libgen.h"
 #endif
@@ -61,6 +62,14 @@
 DEFobjStaticHelpers
 DEFobjCurrIf(errmsg)
 
+/* we must ensure that only one thread at one time tries to load or unload
+ * modules, otherwise we may see race conditions. This first came up with
+ * imdiag/imtcp, which both use the same stream drivers. Below is the mutex
+ * for that handling.
+ * rgerhards, 2009-05-25
+ */
+static pthread_mutex_t mutLoadUnload;
+
 static modInfo_t *pLoadedModules = NULL;	/* list of currently-loaded modules */
 static modInfo_t *pLoadedModulesLast = NULL;	/* tail-pointer */
 
@@ -479,6 +488,8 @@ modUnlinkAndDestroy(modInfo_t **ppThis)
 	pThis = *ppThis;
 	assert(pThis != NULL);
 
+	pthread_mutex_lock(&mutLoadUnload);
+
 	/* first check if we are permitted to unload */
 	if(pThis->eType == eMOD_LIB) {
 		if(pThis->uRefCnt > 0) {
@@ -513,6 +524,7 @@ modUnlinkAndDestroy(modInfo_t **ppThis)
 	moduleDestruct(pThis);
 
 finalize_it:
+	pthread_mutex_unlock(&mutLoadUnload);
 	RETiRet;
 }
 
@@ -587,6 +599,8 @@ Load(uchar *pModName)
 	assert(pModName != NULL);
 	dbgprintf("Requested to load module '%s'\n", pModName);
 
+	pthread_mutex_lock(&mutLoadUnload);
+
 	iModNameLen = strlen((char *) pModName);
 	if(iModNameLen > 3 && !strcmp((char *) pModName + iModNameLen - 3, ".so")) {
 		iModNameLen -= 3;
@@ -696,6 +710,7 @@ Load(uchar *pModName)
 	}
 
 finalize_it:
+	pthread_mutex_unlock(&mutLoadUnload);
 	RETiRet;
 }
 
@@ -791,6 +806,7 @@ BEGINObjClassExit(module, OBJ_IS_LOADABLE_MODULE) /* CHANGE class also in END MA
 CODESTARTObjClassExit(module)
 	/* release objects we no longer need */
 	objRelease(errmsg, CORE_COMPONENT);
+	pthread_mutex_destroy(&mutLoadUnload);
 
 #	ifdef DEBUG
 	modUsrPrintAll(); /* debug aid - TODO: integrate with debug.c, at least the settings! */
@@ -833,6 +849,7 @@ ENDobjQueryInterface(module)
  */
 BEGINAbstractObjClassInit(module, 1, OBJ_IS_CORE_MODULE) /* class, version - CHANGE class also in END MACRO! */
 	uchar *pModPath;
+	pthread_mutexattr_t mutAttr;
 
 	/* use any module load path specified in the environment */
 	if((pModPath = (uchar*) getenv("RSYSLOG_MODDIR")) != NULL) {
@@ -850,6 +867,10 @@ BEGINAbstractObjClassInit(module, 1, OBJ_IS_CORE_MODULE) /* class, version - CHA
 		SetModDir(glblModPath);
 	}
 
+	pthread_mutexattr_init(&mutAttr);
+	pthread_mutexattr_settype(&mutAttr, PTHREAD_MUTEX_RECURSIVE);
+	pthread_mutex_init(&mutLoadUnload, &mutAttr);
+
 	/* request objects we use */
 	CHKiRet(objUse(errmsg, CORE_COMPONENT));
 ENDObjClassInit(module)