The patch titled
Subject: pidns: guarantee that the pidns init will be the last pidns process reaped
has been removed from the -mm tree. Its filename was
pidns-guarantee-that-the-pidns-init-will-be-the-last-pidns-process-reaped.patch
This patch was dropped because an updated version will be merged
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
From: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Subject: pidns: guarantee that the pidns init will be the last pidns process reaped
This change extends the thread group zombie leader logic to work for pid
namespaces. The task with pid 1 is declared the pid namespace leader. A
pid namespace with no more processes is detected by observing that the
init task is a zombie in an empty thread group, and the the init task has
no children.
Instead of moving lingering EXIT_DEAD tasks off of init's ->children list
we now block init from exiting until those children have self reaped and
have removed themselves. Which guarantees that the init task is the last
task in a pid namespace to be reaped.
Signed-off-by: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Cc: Cyrill Gorcunov <gorcunov@xxxxxxxxxx>
Cc: Louis Rilling <louis.rilling@xxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/exit.c | 46 +++++++++++++++++++++++++++++++++++-----------
1 file changed, 35 insertions(+), 11 deletions(-)
diff -puN kernel/exit.c~pidns-guarantee-that-the-pidns-init-will-be-the-last-pidns-process-reaped kernel/exit.c
--- a/kernel/exit.c~pidns-guarantee-that-the-pidns-init-will-be-the-last-pidns-process-reaped
+++ a/kernel/exit.c
@@ -164,6 +164,16 @@ static void delayed_put_task_struct(stru
put_task_struct(tsk);
}
+static bool pidns_leader(struct task_struct *tsk)
+{
+ return is_child_reaper(task_pid(tsk));
+}
+
+static bool delay_pidns_leader(struct task_struct *tsk)
+{
+ return pidns_leader(tsk) &&
+ (!thread_group_empty(tsk) || !list_empty(&tsk->children));
+}
void release_task(struct task_struct * p)
{
@@ -183,15 +193,23 @@ repeat:
__exit_signal(p);
/*
- * If we are the last non-leader member of the thread
- * group, and the leader is zombie, then notify the
- * group leader's parent process. (if it wants notification.)
+ * If we are the last non-leader member of the thread group,
+ * or the last non-leader member of the pid namespace, and the
+ * leader is zombie, then notify the leader's parent
+ * process. (if it wants notification.)
*/
zap_leader = 0;
- leader = p->group_leader;
- if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
+ leader = NULL;
+ /* Do we need to worry about our thread_group or our pidns leader? */
+ if (p != p->group_leader)
+ leader = p->group_leader;
+ else if (pidns_leader(p->real_parent))
+ leader = p->real_parent;
+
+ if (leader && thread_group_empty(leader) &&
+ leader->exit_state == EXIT_ZOMBIE && list_empty(&leader->children)) {
/*
- * If we were the last child thread and the leader has
+ * If we were the last task in the group and the leader has
* exited already, and the leader's parent ignores SIGCHLD,
* then we are the one who should release the leader.
*/
@@ -720,11 +738,10 @@ static struct task_struct *find_new_reap
zap_pid_ns_processes(pid_ns);
write_lock_irq(&tasklist_lock);
/*
- * We can not clear ->child_reaper or leave it alone.
- * There may by stealth EXIT_DEAD tasks on ->children,
- * forget_original_parent() must move them somewhere.
+ * Move all lingering EXIT_DEAD tasks onto the
+ * children list of init's thread group leader.
*/
- pid_ns->child_reaper = init_pid_ns.child_reaper;
+ pid_ns->child_reaper = father->group_leader;
} else if (father->signal->has_child_subreaper) {
struct task_struct *reaper;
@@ -798,6 +815,12 @@ static void forget_original_parent(struc
exit_ptrace(father);
reaper = find_new_reaper(father);
+ /* Return immediately if we aren't going to reparent anything */
+ if (unlikely(reaper == father)) {
+ write_unlock_irq(&tasklist_lock);
+ return;
+ }
+
list_for_each_entry_safe(p, n, &father->children, sibling) {
struct task_struct *t = p;
do {
@@ -853,6 +876,7 @@ static void exit_notify(struct task_stru
autoreap = do_notify_parent(tsk, sig);
} else if (thread_group_leader(tsk)) {
autoreap = thread_group_empty(tsk) &&
+ !delay_pidns_leader(tsk) &&
do_notify_parent(tsk, tsk->exit_signal);
} else {
autoreap = true;
@@ -1583,7 +1607,7 @@ static int wait_consider_task(struct wai
}
/* we don't reap group leaders with subthreads */
- if (!delay_group_leader(p))
+ if (!delay_group_leader(p) && !delay_pidns_leader(p))
return wait_task_zombie(wo, p);
/*
_
Patches currently in -mm which might be from ebiederm@xxxxxxxxxxxx are
origin.patch
linux-next.patch
cred-remove-task_is_dead-from-__task_cred-validation.patch
pidns-use-task_active_pid_ns-in-do_notify_parent.patch
pidns-make-killed-children-autoreap.patch
pidns-make-killed-children-autoreap-checkpatch-fixes.patch
syscalls-x86-add-__nr_kcmp-syscall-v8.patch
c-r-procfs-add-arg_start-end-env_start-end-and-exit_code-members-to-proc-pid-stat.patch
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