Received-SPF: pass (google.com: domain of linux-kernel+bounces-207027-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.48.161 as permitted sender) client-ip=147.75.48.161;
Date: Sat, 8 Jun 2024 14:06:16 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Rachel Menge <rachelmenge@linux.microsoft.com>
Cc: linux-kernel@vger.kernel.org, rcu@vger.kernel.org,
	Wei Fu <fuweid89@gmail.com>, apais@linux.microsoft.com,
	Sudhanva Huruli <Sudhanva.Huruli@microsoft.com>,
	Jens Axboe <axboe@kernel.dk>,
	Christian Brauner <brauner@kernel.org>,
	Mike Christie <michael.christie@oracle.com>,
	Joel Granados <j.granados@samsung.com>,
	Mateusz Guzik <mjguzik@gmail.com>,
	"Paul E. McKenney" <paulmck@kernel.org>,
	Frederic Weisbecker <frederic@kernel.org>,
	Neeraj Upadhyay <neeraj.upadhyay@kernel.org>,
	Joel Fernandes <joel@joelfernandes.org>,
	Josh Triplett <josh@joshtriplett.org>,
	Boqun Feng <boqun.feng@gmail.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Lai Jiangshan <jiangshanlai@gmail.com>,
	Zqiang <qiang.zhang1211@gmail.com>
Subject: [PATCH] zap_pid_ns_processes: clear TIF_NOTIFY_SIGNAL along with
 TIF_SIGPENDING
Message-ID: <20240608120616.GB7947@redhat.com>
References: <1386cd49-36d0-4a5c-85e9-bc42056a5a38@linux.microsoft.com>
Precedence: bulk
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <1386cd49-36d0-4a5c-85e9-bc42056a5a38@linux.microsoft.com>
User-Agent: Mutt/1.5.24 (2015-08-30)

kernel_wait4() doesn't sleep and returns -EINTR if there is no
eligible child and signal_pending() is true.

That is why zap_pid_ns_processes() clears TIF_SIGPENDING but this is not
enough, it should also clear TIF_NOTIFY_SIGNAL to make signal_pending()
return false and avoid a busy-wait loop.

Fixes: 12db8b690010 ("entry: Add support for TIF_NOTIFY_SIGNAL")
Reported-by: Rachel Menge <rachelmenge@linux.microsoft.com>
Closes: https://lore.kernel.org/all/1386cd49-36d0-4a5c-85e9-bc42056a5a38@linux.microsoft.com/
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
---
 kernel/pid_namespace.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/pid_namespace.c b/kernel/pid_namespace.c
index dc48fecfa1dc..25f3cf679b35 100644
--- a/kernel/pid_namespace.c
+++ b/kernel/pid_namespace.c
@@ -218,6 +218,7 @@ void zap_pid_ns_processes(struct pid_namespace *pid_ns)
 	 */
 	do {
 		clear_thread_flag(TIF_SIGPENDING);
+		clear_thread_flag(TIF_NOTIFY_SIGNAL);
 		rc = kernel_wait4(-1, NULL, __WALL, NULL);
 	} while (rc != -ECHILD);
 
-- 
2.25.1.362.g51ebf55