The quilt patch titled
Subject: zap_pid_ns_processes: don't send SIGKILL to sub-threads
has been removed from the -mm tree. Its filename was
zap_pid_ns_processes-dont-send-sigkill-to-sub-threads.patch
This patch was dropped because an updated version will be merged
------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: zap_pid_ns_processes: don't send SIGKILL to sub-threads
Date: Sat, 8 Jun 2024 17:48:35 +0200
The comment above the idr_for_each_entry_continue() loop tries to explain
why we have to signal each thread in the namespace, but it is outdated.
This code no longer uses kill_proc_info(), we have a target task so we can
check thread_group_leader() and avoid the unnecessary group_send_sig_info.
Better yet, we can change pid_task() to use PIDTYPE_TGID rather than
_PID, this way it returns NULL if this pid is not a group-leader pid.
Also, change this code to check SIGNAL_GROUP_EXIT, the exiting process /
thread doesn't necessarily has a pending SIGKILL. Either way these checks
are racy without siglock, so the patch uses data_race() to shut up KCSAN.
Link: https://lkml.kernel.org/r/20240608154835.GD7947@xxxxxxxxxx
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Allen Pais <apais@xxxxxxxxxxxxxxxxxxx>
Cc: Boqun Feng <boqun.feng@xxxxxxxxx>
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Frederic Weisbecker <frederic@xxxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Joel Fernandes (Google) <joel@xxxxxxxxxxxxxxxxx>
Cc: Joel Granados <j.granados@xxxxxxxxxxx>
Cc: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Cc: Lai Jiangshan <jiangshanlai@xxxxxxxxx>
Cc: Mateusz Guzik <mjguzik@xxxxxxxxx>
Cc: Mathieu Desnoyers <mathieu.desnoyers@xxxxxxxxxxxx>
Cc: Mike Christie <michael.christie@xxxxxxxxxx>
Cc: Neeraj Upadhyay <neeraj.upadhyay@xxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxx>
Cc: Steven Rostedt (Google) <rostedt@xxxxxxxxxxx>
Cc: Wei Fu <fuweid89@xxxxxxxxx>
Cc: Zqiang <qiang.zhang1211@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/pid_namespace.c | 13 +++----------
1 file changed, 3 insertions(+), 10 deletions(-)
--- a/kernel/pid_namespace.c~zap_pid_ns_processes-dont-send-sigkill-to-sub-threads
+++ a/kernel/pid_namespace.c
@@ -191,21 +191,14 @@ void zap_pid_ns_processes(struct pid_nam
* The last thread in the cgroup-init thread group is terminating.
* Find remaining pid_ts in the namespace, signal and wait for them
* to exit.
- *
- * Note: This signals each threads in the namespace - even those that
- * belong to the same thread group, To avoid this, we would have
- * to walk the entire tasklist looking a processes in this
- * namespace, but that could be unnecessarily expensive if the
- * pid namespace has just a few processes. Or we need to
- * maintain a tasklist for each pid namespace.
- *
*/
rcu_read_lock();
read_lock(&tasklist_lock);
nr = 2;
idr_for_each_entry_continue(&pid_ns->idr, pid, nr) {
- task = pid_task(pid, PIDTYPE_PID);
- if (task && !__fatal_signal_pending(task))
+ task = pid_task(pid, PIDTYPE_TGID);
+ /* reading signal->flags is racy without sighand->siglock */
+ if (task && !(data_race(task->signal->flags) & SIGNAL_GROUP_EXIT))
group_send_sig_info(SIGKILL, SEND_SIG_PRIV, task, PIDTYPE_MAX);
}
read_unlock(&tasklist_lock);
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
