linux-kernel - [PATCH 07/16] signal: Wake up the designated parent

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Date:   Wed, 18 May 2022 17:53:46 -0500
From:   "Eric W. Biederman" <ebiederm@...ssion.com>
To:     linux-kernel@...r.kernel.org
Cc:     rjw@...ysocki.net, Oleg Nesterov <oleg@...hat.com>,
        mingo@...nel.org, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, mgorman@...e.de,
        bigeasy@...utronix.de, Will Deacon <will@...nel.org>,
        tj@...nel.org, linux-pm@...r.kernel.org,
        Peter Zijlstra <peterz@...radead.org>,
        Richard Weinberger <richard@....at>,
        Anton Ivanov <anton.ivanov@...bridgegreys.com>,
        Johannes Berg <johannes@...solutions.net>,
        linux-um@...ts.infradead.org, Chris Zankel <chris@...kel.net>,
        Max Filippov <jcmvbkbc@...il.com>,
        linux-xtensa@...ux-xtensa.org, Kees Cook <keescook@...omium.org>,
        Jann Horn <jannh@...gle.com>, linux-ia64@...r.kernel.org,
        Robert OCallahan <roc@...nos.co>, Kyle Huey <khuey@...nos.co>,
        Richard Henderson <rth@...ddle.net>,
        Ivan Kokshaysky <ink@...assic.park.msu.ru>,
        Matt Turner <mattst88@...il.com>,
        Jason Wessel <jason.wessel@...driver.com>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Douglas Anderson <dianders@...omium.org>,
        Douglas Miller <dougmill@...ux.vnet.ibm.com>,
        Michael Ellerman <mpe@...erman.id.au>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        "Eric W. Biederman" <ebiederm@...ssion.com>
Subject: [PATCH 07/16] signal: Wake up the designated parent

Today if a process is ptraced only the ptracer will ever be woken up in
wait, if the parent is waiting with __WNOTHREAD.  Update the code
so that the real_parent can also be woken up with __WNOTHREAD even
when the code is ptraced.

Fixes: 75b95953a569 ("job control: Add @for_ptrace to do_notify_parent_cldstop()")
Signed-off-by: "Eric W. Biederman" <ebiederm@...ssion.com>
---
 kernel/exit.c | 19 ++++++++++++++-----
 1 file changed, 14 insertions(+), 5 deletions(-)

diff --git a/kernel/exit.c b/kernel/exit.c
index f072959fcab7..0e26f73c49ac 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -1421,26 +1421,35 @@ static int ptrace_do_wait(struct wait_opts *wo, struct task_struct *tsk)
 	return 0;
 }
 
+struct child_wait_info {
+	struct task_struct *p;
+	struct task_struct *parent;
+};
+
 static int child_wait_callback(wait_queue_entry_t *wait, unsigned mode,
 				int sync, void *key)
 {
 	struct wait_opts *wo = container_of(wait, struct wait_opts,
 						child_wait);
-	struct task_struct *p = key;
+	struct child_wait_info *info = key;
 
-	if (!eligible_pid(wo, p))
+	if (!eligible_pid(wo, info->p))
 		return 0;
 
-	if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
-		return 0;
+	if ((wo->wo_flags & __WNOTHREAD) && (wait->private != info->parent))
+			return 0;
 
 	return default_wake_function(wait, mode, sync, key);
 }
 
 void __wake_up_parent(struct task_struct *p, struct task_struct *parent)
 {
+	struct child_wait_info info = {
+		.p = p,
+		.parent = parent,
+	};
 	__wake_up_sync_key(&parent->signal->wait_chldexit,
-			   TASK_INTERRUPTIBLE, p);
+			   TASK_INTERRUPTIBLE, &info);
 }
 
 static bool is_effectively_child(struct wait_opts *wo, bool ptrace,
-- 
2.35.3