- Fix detaching under some circumstances.

  When truss is detaching from very active process it is possible to
  hang on waitpid(2) in restore_proc() forever, because
  ptrace(PT_SYSCALL) must be called before detaching, to allow the
  debugging process to continue execution.  Also when truss called with
  '-c' argument, it does not print anything after detach, because it
  immediately exits from restore_proc().

  To fix these two problems make detaching deferred, but then it is
  impossible to detach from a process which does not do any system call.
  To fix this issue use sigaction(2) instead of signal(3) to disable
  SA_RESTART flag for waitpid(2) that makes it non-restartable.  Remove
  global variable child_pid, because now detaching is handled in context
  where child's pid is known.

Reported by:	mjg
Tested by:	mjg, swills
Approved by:	kib (mentor)
MFC after:	2 weeks

1 files changed, 9 insertions, 4 deletions

diff --git a/usr.bin/truss/main.c b/usr.bin/truss/main.c
index d6a1edc..cb97293 100644
--- a/usr.bin/truss/main.c
+++ b/usr.bin/truss/main.c
@@ -163,6 +163,7 @@ strsig(int sig)
 int
 main(int ac, char **av)
 {
+	struct sigaction sa;
 	struct ex_types *funcs;
 	struct trussinfo *trussinfo;
 	char *fname;
@@ -257,10 +258,13 @@ main(int ac, char **av)
 		signal(SIGTERM, SIG_IGN);
 		signal(SIGQUIT, SIG_IGN);
 	} else {
+		sa.sa_handler = restore_proc;
+		sa.sa_flags = 0;
+		sigemptyset(&sa.sa_mask);
+		sigaction(SIGINT, &sa, NULL);
+		sigaction(SIGQUIT, &sa, NULL);
+		sigaction(SIGTERM, &sa, NULL);
 		start_tracing(trussinfo->pid);
-		signal(SIGINT, restore_proc);
-		signal(SIGTERM, restore_proc);
-		signal(SIGQUIT, restore_proc);
 	}
 
 
@@ -366,7 +370,8 @@ START_TRACE:
 		default:
 			break;
 		}
-	} while (trussinfo->pr_why != S_EXIT);
+	} while (trussinfo->pr_why != S_EXIT &&
+	    trussinfo->pr_why != S_DETACHED);
 
 	if (trussinfo->flags & FOLLOWFORKS) {
 		do {