Handle detach from sleeping or unresponsive processes

5 files changed, 46 insertions, 8 deletions

diff --git a/common.h b/common.h
index 2399e29..b6e10f2 100644
--- a/common.h
+++ b/common.h
@@ -347,7 +347,6 @@ extern void continue_after_signal(pid_t pid, int signum);
 extern void continue_after_syscall(Process *proc, int sysnum, int ret_p);
 extern void continue_after_breakpoint(Process * proc, Breakpoint * sbp);
 extern void continue_after_vfork(Process * proc);
-extern void ltrace_exiting(void);
 extern long gimme_arg(enum tof type, Process * proc, int arg_num, arg_type_info * info);
 extern void save_register_args(enum tof type, Process * proc);
 extern int umovestr(Process * proc, void * addr, int len, void * laddr);
@@ -363,6 +362,22 @@ extern int task_kill (pid_t pid, int sig);
  * any platform-specific knowledge of why it could be so.  */
 void trace_fail_warning(pid_t pid);
 
+/* A pair of functions called to initiate a detachment request when
+ * ltrace is about to exit.  Their job is to undo any effects that
+ * tracing had and eventually detach process, perhaps by way of
+ * installing a process handler.
+ *
+ * OS_LTRACE_EXITING_SIGHANDLER is called from a signal handler
+ * context right after the signal was captured.  It returns 1 if the
+ * request was handled or 0 if it wasn't.
+ *
+ * If the call to OS_LTRACE_EXITING_SIGHANDLER didn't handle the
+ * request, OS_LTRACE_EXITING is called when the next event is
+ * generated.  Therefore it's called in "safe" context, without
+ * re-entrancy concerns, but it's only called after an even is
+ * generated.  */
+int os_ltrace_exiting_sighandler(void);
+void os_ltrace_exiting(void);
 
 extern struct ltelf main_lte;
 
diff --git a/handle_event.c b/handle_event.c
index e3d3d0a..725f50d 100644
--- a/handle_event.c
+++ b/handle_event.c
@@ -49,11 +49,12 @@ call_handler(Process * proc, Event * event)
 }
 
 void
-handle_event(Event *event) {
+handle_event(Event *event)
+{
 	if (exiting == 1) {
-		exiting = 2;
 		debug(1, "ltrace about to exit");
-		ltrace_exiting();
+		os_ltrace_exiting();
+		exiting = 2;
 	}
 	debug(DEBUG_FUNCTION, "handle_event(pid=%d, type=%d)",
 	      event->proc ? event->proc->pid : -1, event->type);
diff --git a/libltrace.c b/libltrace.c
index 19bfafd..777ad1b 100644
--- a/libltrace.c
+++ b/libltrace.c
@@ -48,9 +48,14 @@ signal_alarm(int sig) {
 }
 
 static void
-signal_exit(int sig) {
-	exiting = 1;
+signal_exit(int sig)
+{
 	debug(1, "Received interrupt signal; exiting...");
+	if (exiting != 0)
+		return;
+
+	exiting = 1 + !!os_ltrace_exiting_sighandler();
+
 	signal(SIGINT, SIG_IGN);
 	signal(SIGTERM, SIG_IGN);
 	signal(SIGALRM, signal_alarm);
diff --git a/sysdeps/linux-gnu/events.c b/sysdeps/linux-gnu/events.c
index 021192f..b6c12ef 100644
--- a/sysdeps/linux-gnu/events.c
+++ b/sysdeps/linux-gnu/events.c
@@ -104,6 +104,8 @@ next_qd_event(void)
 	return each_qd_event(&event_process_not_reenabling, NULL);
 }
 
+int linux_in_waitpid = 0;
+
 Event *
 next_event(void)
 {
@@ -124,7 +126,11 @@ next_event(void)
 		debug(DEBUG_EVENT, "event: No more traced programs: exiting");
 		exit(0);
 	}
+
+	linux_in_waitpid = 1;
 	pid = waitpid(-1, &status, __WALL);
+	linux_in_waitpid = 0;
+
 	if (pid == -1) {
 		if (errno == ECHILD) {
 			debug(DEBUG_EVENT, "event: No more traced programs: exiting");
diff --git a/sysdeps/linux-gnu/trace.c b/sysdeps/linux-gnu/trace.c
index 82a4154..9ecea1e 100644
--- a/sysdeps/linux-gnu/trace.c
+++ b/sysdeps/linux-gnu/trace.c
@@ -314,8 +314,8 @@ task_stopped(Process * task, void * data)
 	case ps_invalid:
 	case ps_tracing_stop:
 	case ps_zombie:
-	case ps_sleeping:
 		return pcb_cont;
+	case ps_sleeping:
 	case ps_stop:
 	case ps_other:
 		return pcb_stop;
@@ -1005,7 +1005,7 @@ continue_after_syscall(Process * proc, int sysnum, int ret_p)
  * detaches.
  */
 void
-ltrace_exiting(void)
+os_ltrace_exiting(void)
 {
 	struct opt_p_t * it;
 	for (it = opt_p; it != NULL; it = it->next) {
@@ -1019,6 +1019,17 @@ ltrace_exiting(void)
 	}
 }
 
+int
+os_ltrace_exiting_sighandler(void)
+{
+	extern int linux_in_waitpid;
+	if (linux_in_waitpid) {
+		os_ltrace_exiting();
+		return 1;
+	}
+	return 0;
+}
+
 size_t
 umovebytes(Process *proc, void *addr, void *laddr, size_t len) {