Introduced the notion of a currently debugged thread in the kernel

debugger and added respective getter/setter methods
debug_{get,set}_debugged_thread(). By default the currently debugged
thread is the thread that dropped into the kernel debugger, but commands
like "in_context" can change it.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@27164 a95241bf-73f2-0310-859d-f6bbb57e9c96

headers/private/kernel/debug.h

@@ -129,6 +129,9 @@ extern bool		print_debugger_command_usage(const char* command);
 extern void debug_set_demangle_hook(const char *(*hook)(const char *));
 extern const char *debug_demangle(const char *);
 
+extern struct thread* debug_set_debugged_thread(struct thread* thread);
+extern struct thread* debug_get_debugged_thread();
+
 extern void		_user_debug_output(const char *userString);
 
 #ifdef __cplusplus

src/system/kernel/debug/debug.cpp

@@ -93,6 +93,8 @@ static int32 sCurrentLine = 0;
 
 static const char *(*sDemangleHook)(const char *) = NULL;
 
+static struct thread* sDebuggedThread;
+
 #define distance(a, b) ((a) < (b) ? (b) - (a) : (a) - (b))
 
 
@@ -1216,6 +1218,8 @@ kernel_debugger(const char *message)
 
 	sDebugOutputFilter = &gDefaultDebugOutputFilter;
 
+	sDebuggedThread = NULL;
+
 	if (message)
 		kprintf("PANIC: %s\n", message);
 
@@ -1426,6 +1430,23 @@ debug_demangle(const char *sym)
 }
 
 
+struct thread*
+debug_set_debugged_thread(struct thread* thread)
+{
+	struct thread* previous = sDebuggedThread;
+	sDebuggedThread = thread;
+	return previous;
+}
+
+
+struct thread*
+debug_get_debugged_thread()
+{
+	return sDebuggedThread != NULL
+		? sDebuggedThread : thread_get_current_thread();
+}
+
+
 //	#pragma mark -
 //	userland syscalls