Re: [path][rfc] add PR_DETACH prctl command [1/3]

[Stas Sergeev <stsp@aknet.ru>]

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Reposting per Oleg's request.

The attached patch adds do_signal_parent() function.
It is the same as do_notify_parent(), but can be used
when the child is not terminating, but (for example)
detaches with PR_DETACH.

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diff --git a/include/linux/sched.h b/include/linux/sched.h
index 777d8a5..e74882f 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -2096,6 +2096,7 @@ extern int kill_pgrp(struct pid *pid, int sig, int priv);
 extern int kill_pid(struct pid *pid, int sig, int priv);
 extern int kill_proc_info(int, struct siginfo *, pid_t);
 extern int do_notify_parent(struct task_struct *, int);
+extern int do_signal_parent(struct task_struct *, int, int, int);
 extern void __wake_up_parent(struct task_struct *p, struct task_struct *parent);
 extern void force_sig(int, struct task_struct *);
 extern int send_sig(int, struct task_struct *, int);
diff --git a/kernel/signal.c b/kernel/signal.c
index 4e3cff1..54b93c7 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -1434,14 +1434,8 @@ ret:
 	return ret;
 }
 
-/*
- * Let a parent know about the death of a child.
- * For a stopped/continued status change, use do_notify_parent_cldstop instead.
- *
- * Returns -1 if our parent ignored us and so we've switched to
- * self-reaping, or else @sig.
- */
-int do_notify_parent(struct task_struct *tsk, int sig)
+int do_signal_parent(struct task_struct *tsk, int sig, int sicode,
+	int sistatus)
 {
 	struct siginfo info;
 	unsigned long flags;
@@ -1450,11 +1444,8 @@ int do_notify_parent(struct task_struct *tsk, int sig)
 
 	BUG_ON(sig == -1);
 
- 	/* do_notify_parent_cldstop should have been called instead.  */
- 	BUG_ON(task_is_stopped_or_traced(tsk));
-
-	BUG_ON(!task_ptrace(tsk) &&
-	       (tsk->group_leader != tsk || !thread_group_empty(tsk)));
+	/* do_notify_parent_cldstop should have been called instead.  */
+	BUG_ON(task_is_stopped_or_traced(tsk));
 
 	info.si_signo = sig;
 	info.si_errno = 0;
@@ -1480,15 +1471,8 @@ int do_notify_parent(struct task_struct *tsk, int sig)
 	info.si_stime = cputime_to_clock_t(cputime_add(tsk->stime,
 				tsk->signal->stime));
 
-	info.si_status = tsk->exit_code & 0x7f;
-	if (tsk->exit_code & 0x80)
-		info.si_code = CLD_DUMPED;
-	else if (tsk->exit_code & 0x7f)
-		info.si_code = CLD_KILLED;
-	else {
-		info.si_code = CLD_EXITED;
-		info.si_status = tsk->exit_code >> 8;
-	}
+	info.si_code = sicode;
+	info.si_status = sistatus;
 
 	psig = tsk->parent->sighand;
 	spin_lock_irqsave(&psig->siglock, flags);
@@ -1510,9 +1494,11 @@ int do_notify_parent(struct task_struct *tsk, int sig)
 		 * is implementation-defined: we do (if you don't want
 		 * it, just use SIG_IGN instead).
 		 */
-		ret = tsk->exit_signal = -1;
+		tsk->exit_signal = -1;
 		if (psig->action[SIGCHLD-1].sa.sa_handler == SIG_IGN)
 			sig = -1;
+		/* reap process now, rather than promoting to zombie */
+		ret = DEATH_REAP;
 	}
 	if (valid_signal(sig) && sig > 0)
 		__group_send_sig_info(sig, &info, tsk->parent);
@@ -1522,6 +1508,33 @@ int do_notify_parent(struct task_struct *tsk, int sig)
 	return ret;
 }
 
+/*
+ * Let a parent know about the death of a child.
+ * For a stopped/continued status change, use do_notify_parent_cldstop instead.
+ *
+ * Returns -1 if our parent ignored us and so we've switched to
+ * self-reaping, or else @sig.
+ */
+int do_notify_parent(struct task_struct *tsk, int sig)
+{
+	int sicode, sistatus;
+
+	BUG_ON(!task_ptrace(tsk) &&
+	       (tsk->group_leader != tsk || !thread_group_empty(tsk)));
+
+	sistatus = tsk->exit_code & 0x7f;
+	if (tsk->exit_code & 0x80)
+		sicode = CLD_DUMPED;
+	else if (tsk->exit_code & 0x7f)
+		sicode = CLD_KILLED;
+	else {
+		sicode = CLD_EXITED;
+		sistatus = tsk->exit_code >> 8;
+	}
+
+	return do_signal_parent(tsk, sig, sicode, sistatus);
+}
+
 static void do_notify_parent_cldstop(struct task_struct *tsk, int why)
 {
 	struct siginfo info;