linux-kernel-markers-documentation-update-flags

@@ -78,6 +78,21 @@ which saves a data cache hit, but also requires cross CPU code modification. In
 order to support embedded systems which use read-only memory for their code, the
 optimization can be disabled through menu options.
 
+The MF_* flags can be used to control the type of marker. See the
+include/marker.h header for the list of flags. They can be specified as the
+first parameter of the _MARK() macro, such as the following example which is
+safe wrt lockdep.c (useful for marking lockdep.c functions).
+
+_MARK(_MF_DEFAULT | ~_MF_LOCKDEP, subsystem_eventb,
+  MARK_NOARGS);
+
+Another example is to specify that a specific marker must never call printk :
+_MARK(_MF_DEFAULT | ~_MF_PRINTK, subsystem_eventc,
+  "%d %s %p[struct task_struct]",
+  someint, somestring, current);
+
+Flag compatibility is checked before connecting the probe to the marker.
+
 
 * Probe example
 

@@ -122,6 +137,13 @@ void probe_subsystem_event(const char *format, ...)
 	va_end(ap);
 }
 
+#define SUBSYSTEM_EVENTB_FORMAT MARK_NOARGS
+void probe_subsystem_eventb(const char *format, ...)
+{
+	/* Increment counters, trace, ... but _never_ generate a call to
+	 * lockdep.c ! */
+}
+
 static int __init probe_init(void)
 {
 	int result;

@@ -130,16 +152,24 @@ static int __init probe_init(void)
 			probe_subsystem_event);
 	if (!result)
 		goto cleanup;
+	result = _marker_set_probe(_MF_DEFAULT & ~_MF_LOCKDEP,
+			"subsystem_eventb",
+			SUBSYSTEM_EVENTB_FORMAT,
+			probe_subsystem_eventb);
+	if (!result)
+		goto cleanup;
 	return 0;
 
 cleanup:
 	marker_remove_probe(probe_subsystem_event);
+	marker_remove_probe(probe_subsystem_eventb);
 	return -EPERM;
 }
 
 static void __exit probe_fini(void)
 {
 	marker_remove_probe(probe_subsystem_event);
+	marker_remove_probe(probe_subsystem_eventb);
 }
 
 module_init(probe_init);