If ->report_xxx() returns UTRACE_STOP the tracee will do utrace_stop
eventually. But how can the tracer know the tracee is already
TASK_TRACED/->stopped?
(except it can check utrace_control(UTRACE_STOP) in a loop of course).
Actually, I am asking because this chunk from utrace-ptrace.patch
+#ifdef CONFIG_UTRACE_PTRACE
+ /*
+ * If ptrace is among the reasons for this stop, do its
+ * notification now. This could not just be done in
+ * ptrace's own event report callbacks because it has to
+ * be done after we are in TASK_TRACED. This makes the
+ * synchronization with ptrace_do_wait() work right.
+ */
+ if (((task->ptrace >> 16) & UTRACE_RESUME_MASK) ==
+ UTRACE_RESUME - UTRACE_STOP) {
+ read_lock(&tasklist_lock);
+ do_notify_parent_cldstop(task, CLD_TRAPPED);
+ read_unlock(&tasklist_lock);
+ }
+#endif
Looks like a horrible hack, imho. Utrace should know nothing about
ptrace.
Can't we do something like
--- include/linux/utrace.h
+++ include/linux/utrace.h
@@ -170,6 +170,7 @@ void task_utrace_proc_status(struct seq_
*/
enum utrace_resume_action {
UTRACE_STOP,
+ UTRACE_STOP_NOTIFY,
UTRACE_REPORT,
UTRACE_INTERRUPT,
UTRACE_SINGLESTEP,
@@ -512,6 +513,9 @@ static inline void utrace_engine_put(str
* parent by blocking.
*/
struct utrace_engine_ops {
+ // SPECIAL!!! must not block/etc
+ void (*notify_stopped)(...);
+
u32 (*report_quiesce)(enum utrace_resume_action action,
struct utrace_engine *engine,
struct task_struct *task,
--- kernel/utrace.c
+++ kernel/utrace.c
@@ -419,6 +419,13 @@ static bool utrace_stop(struct task_stru
spin_unlock_irq(&task->sighand->siglock);
spin_unlock(&utrace->lock);
+ list_for_each_entry(engine) {
+ if (engine_wants_notify_stopped(engine)) {
+ clear_engine_wants_notify_stopped(engine);
+ engine->ops->notify_stopped(...);
+ }
+ }
+
schedule();
@@ -1348,6 +1355,11 @@ static bool finish_callback(struct utrac
{
enum utrace_resume_action action = utrace_resume_action(ret);
+ if (action == UTRACE_STOP_NOTIFY) {
+ mark_engine_wants_notify_stopped(engine);
+ action = UTRACE_STOP;
+ }
+
report->result = ret & ~UTRACE_RESUME_MASK;
/*
?
Or do you think this doesn't make sense?
(of course, the "patch" above is just to explain what I mean, we need more
changes with ENGINE_STOP mask, utrace_control, utrace_set_events, etc).
Oleg.
