2007-07-05 Jan Kratochvil <jan.kratochvil@redhat.com>

	* strace.c (detach): New prototype.  Extended the function comment.
	[LINUX] (detach): Call droptcb() instead of the wrongly parametrized
	detach() call.
	(handle_group_exit): Call droptcb() instead of the wrongly parametrized
	detach() call.	Always call detach() only once from the group leader.
	Comment the leader killing known bug tested by `test/leaderkill.c'.
	Code advisory: Roland McGrath
	Fixes RH#240961.

diff --git a/strace.c b/strace.c
index 4e8604038dc8b00dd010898778f560d29df513cf..ce982dc6e5fb7f0835cfbb3012a9942ff54539e4 100644 (file)
--- a/strace.c
+++ b/strace.c
@@ -98,6 +98,7 @@ unsigned int nprocs, tcbtabsize;
 char *progname;
 extern char **environ;
 
+static int detach P((struct tcb *tcp, int sig));
 static int trace P((void));
 static void cleanup P((void));
 static void interrupt P((int sig));
@@ -1332,7 +1333,10 @@ struct tcb *tcp;
 
 #endif /* !USE_PROCFS */
 
-/* detach traced process; continue with sig */
+/* detach traced process; continue with sig
+   Never call DETACH twice on the same process as both unattached and
+   attached-unstopped processes give the same ESRCH.  For unattached process we
+   would SIGSTOP it and wait for its SIGSTOP notification forever.  */
 
 static int
 detach(tcp, sig)
@@ -1521,8 +1525,10 @@ int sig;
        droptcb(tcp);
 
 #ifdef LINUX
-       if (zombie != NULL)
-               error = detach(zombie) || error;
+       if (zombie != NULL) {
+               /* TCP no longer exists therefore you must not detach () it.  */
+               droptcb(zombie);
+       }
 #endif
 
        return error;
@@ -2096,14 +2102,16 @@ handle_group_exit(struct tcb *tcp, int sig)
                        fprintf(stderr,
                                "PANIC: handle_group_exit: %d leader %d\n",
                                tcp->pid, leader ? leader->pid : -1);
-               detach(tcp);    /* Already died.  */
+               /* TCP no longer exists therefore you must not detach () it.  */
+               droptcb(tcp);   /* Already died.  */
        }
        else {
                /* Mark that we are taking the process down.  */
                tcp->flags |= TCB_EXITING | TCB_GROUP_EXITING;
                if (tcp->flags & TCB_ATTACHED) {
                        if (leader != NULL && leader != tcp) {
-                               if (leader->flags & TCB_ATTACHED) {
+                               if ((leader->flags & TCB_ATTACHED) &&
+                                   !(leader->flags & TCB_EXITING)) {
                                        /* We need to detach the leader so
                                           that the process death will be
                                           reported to its real parent.
@@ -2115,7 +2123,10 @@ handle_group_exit(struct tcb *tcp, int sig)
                                           stopped.  Then the value we pass
                                           in PTRACE_DETACH just sets the
                                           death signal reported to the
-                                          real parent.  */
+                                          real parent.
+                                          FIXME: This killing gets caught by
+                                          WAITPID of the leader's parent.
+                                          Testcase: test/leaderkill.c  */
                                        ptrace(PTRACE_KILL, leader->pid, 0, 0);
                                        if (debug)
                                                fprintf(stderr,