Race condition during JVMTI shutdown results in rare GPF or other Program Error

No diagnostics are available for this issue, furthermore the issue will be very hard to reproduce unless running on the z/TPF platform. The primary reason is how the z/TPF scheduler works compared to other platforms in that it drives different timing scenarios.

However, the good news is the general problem area has been identified. Below are the two areas that require some kind of synchronization.

openj9/runtime/jvmti/jvmtiHook.c

Lines 2919 to 2925 in 50425f8

    
           while (nativeLibrary != NULL) { 
        
           	callback(currentThread, nativeMethod, nativeLibrary, longJNI, shortJNI, functionArgCount, TRUE); 
        
           	if (J9_NATIVE_METHOD_IS_BOUND(nativeMethod)) { 
        
           		goto done; 
        
           	} 
        
           	nativeLibrary = nativeLibrary->next; 
        
           }

openj9/runtime/jvmti/jvmtiStartup.c

Lines 1026 to 1077 in 50425f8

    
           	if (jvmtiData->agentLibraries != NULL) { 
        
           		PORT_ACCESS_FROM_JAVAVM(vm); 
        
           		J9JVMTIAgentLibrary * agentLibrary; 
        
           		pool_state state; 
        
           		agentLibrary = pool_startDo(jvmtiData->agentLibraries, &state); 
        
           		while(agentLibrary) { 
        
           			if (agentLibrary->nativeLib.handle != 0) { 
        
           				void (JNICALL * onUnload)(J9JavaVM *); 
        
           				/* If the agent was loaded/attached through static linking, check for the 
        
           				 * presence of Agent_OnUnload_L.  If this cannot be found, go on to look for 
        
           				 * Agent_OnUnload, or else invoke Agent_OnUnload_L. 
        
           				 */ 
        
           				if (J9NATIVELIB_LINK_MODE_STATIC == agentLibrary->nativeLib.linkMode) { 
        
           					j9str_printf( 
        
           							nameBuffer, 
        
           							sizeof(nameBuffer), 
        
           							"%s_%s", 
        
           							J9JVMTI_AGENT_ONUNLOAD, 
        
           							agentLibrary->nativeLib.name); 
        
           				} else /* J9NATIVELIB_LINK_MODE_DYNAMIC == linkMode */ { 
        
           					strcpy(nameBuffer, J9JVMTI_AGENT_ONUNLOAD); 
        
           				} 
        
           				if (j9sl_lookup_name(agentLibrary->nativeLib.handle, nameBuffer, (void *) &onUnload, "VL") == 0) { 
        
           					UDATA loadCount; 
        
           					Trc_JVMTI_shutDownAgentLibraries_invokingAgentShutDown(nameBuffer); 
        
           					for (loadCount = 0; loadCount < agentLibrary->loadCount; loadCount++) { 
        
           						onUnload(vm); 
        
           					} 
        
           				} 
        
           				if (closeLibrary && (agentLibrary->xRunLibrary == NULL)) { 
        
           					j9sl_close_shared_library(agentLibrary->nativeLib.handle); 
        
           				} 
        
           			} 
        
           			if (agentLibrary->xRunLibrary == NULL) { 
        
           				j9mem_free_memory(agentLibrary->nativeLib.name); 
        
           			} 
        
           			/* Jazz 99339: release memory allocated for J9InvocationJavaVM in issueAgentOnLoadAttach() */ 
        
           			if (NULL != agentLibrary->invocationJavaVM) { 
        
           				j9mem_free_memory(agentLibrary->invocationJavaVM); 
        
           				agentLibrary->invocationJavaVM = NULL; 
        
           			} 
        
           			agentLibrary = pool_nextDo(&state); 
        
           		} 
        
           		pool_kill(jvmtiData->agentLibraries); 
        
           		jvmtiData->agentLibraries = NULL; 
        
           	}

The problem encountered is that the nativeLibrary linked list is in the middle of being cleaned up by JVMTI shutdown processing while simultaneously being accessed in jvmtiHook. The simultaneous access leads to undefined behavior.

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

Uh oh!

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

	while (nativeLibrary != NULL) {
	callback(currentThread, nativeMethod, nativeLibrary, longJNI, shortJNI, functionArgCount, TRUE);
	if (J9_NATIVE_METHOD_IS_BOUND(nativeMethod)) {
	goto done;
	}
	nativeLibrary = nativeLibrary->next;
	}

	if (jvmtiData->agentLibraries != NULL) {
	PORT_ACCESS_FROM_JAVAVM(vm);
	J9JVMTIAgentLibrary * agentLibrary;
	pool_state state;

	agentLibrary = pool_startDo(jvmtiData->agentLibraries, &state);
	while(agentLibrary) {
	if (agentLibrary->nativeLib.handle != 0) {
	void (JNICALL * onUnload)(J9JavaVM *);

	/* If the agent was loaded/attached through static linking, check for the
	* presence of Agent_OnUnload_L. If this cannot be found, go on to look for
	* Agent_OnUnload, or else invoke Agent_OnUnload_L.
	*/
	if (J9NATIVELIB_LINK_MODE_STATIC == agentLibrary->nativeLib.linkMode) {
	j9str_printf(
	nameBuffer,
	sizeof(nameBuffer),
	"%s_%s",
	J9JVMTI_AGENT_ONUNLOAD,
	agentLibrary->nativeLib.name);
	} else /* J9NATIVELIB_LINK_MODE_DYNAMIC == linkMode */ {
	strcpy(nameBuffer, J9JVMTI_AGENT_ONUNLOAD);
	}

	if (j9sl_lookup_name(agentLibrary->nativeLib.handle, nameBuffer, (void *) &onUnload, "VL") == 0) {
	UDATA loadCount;

	Trc_JVMTI_shutDownAgentLibraries_invokingAgentShutDown(nameBuffer);
	for (loadCount = 0; loadCount < agentLibrary->loadCount; loadCount++) {
	onUnload(vm);
	}
	}
	if (closeLibrary && (agentLibrary->xRunLibrary == NULL)) {
	j9sl_close_shared_library(agentLibrary->nativeLib.handle);
	}
	}
	if (agentLibrary->xRunLibrary == NULL) {
	j9mem_free_memory(agentLibrary->nativeLib.name);
	}

	/* Jazz 99339: release memory allocated for J9InvocationJavaVM in issueAgentOnLoadAttach() */
	if (NULL != agentLibrary->invocationJavaVM) {
	j9mem_free_memory(agentLibrary->invocationJavaVM);
	agentLibrary->invocationJavaVM = NULL;
	}

	agentLibrary = pool_nextDo(&state);
	}
	pool_kill(jvmtiData->agentLibraries);
	jvmtiData->agentLibraries = NULL;
	}

Description

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions