The patch titled
Subject: pidns: find_new_reaper() can no longer switch to init_pid_ns.child_reaper
has been added to the -mm tree. Its filename is
pidns-find_new_reaper-can-no-longer-switch-to-init_pid_nschild_reaper.patch
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------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: pidns: find_new_reaper() can no longer switch to init_pid_ns.child_reaper
find_new_reaper() changes pid_ns->child_reaper, see add0d4df ("pid_ns:
zap_pid_ns_processes: fix the ->child_reaper changing").
The original reason has gone away after the previous patch, ->children
list must be empty after zap_pid_ns_processes().
However now we can not switch to init_pid_ns.child_reaper.
__unhash_process() relies on the "->child_reaper == parent" check, but
this check does not work if the last exiting task is also the child
reaper.
As Eric sugested, we can change __unhash_process() to use the parent's
pid_ns and remove this code.
Also, with this change we can move detach_pid(PIDTYPE_PID) back, where it
was before the previous fix.
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: "Eric W. Biederman" <ebiederm@xxxxxxxxxxxx>
Cc: Louis Rilling <louis.rilling@xxxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Acked-by: Pavel Emelyanov <xemul@xxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
kernel/exit.c | 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)
diff -puN kernel/exit.c~pidns-find_new_reaper-can-no-longer-switch-to-init_pid_nschild_reaper kernel/exit.c
--- a/kernel/exit.c~pidns-find_new_reaper-can-no-longer-switch-to-init_pid_nschild_reaper
+++ a/kernel/exit.c
@@ -64,6 +64,7 @@ static void exit_mm(struct task_struct *
static void __unhash_process(struct task_struct *p, bool group_dead)
{
nr_threads--;
+ detach_pid(p, PIDTYPE_PID);
if (group_dead) {
detach_pid(p, PIDTYPE_PGID);
detach_pid(p, PIDTYPE_SID);
@@ -78,13 +79,12 @@ static void __unhash_process(struct task
if (IS_ENABLED(CONFIG_PID_NS)) {
struct task_struct *parent = p->real_parent;
- if ((task_active_pid_ns(p)->child_reaper == parent) &&
+ if ((task_active_pid_ns(parent)->child_reaper == parent) &&
list_empty(&parent->children) &&
(parent->flags & PF_EXITING))
wake_up_process(parent);
}
}
- detach_pid(p, PIDTYPE_PID);
list_del_rcu(&p->thread_group);
}
@@ -732,12 +732,6 @@ 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.
- */
- pid_ns->child_reaper = init_pid_ns.child_reaper;
} else if (father->signal->has_child_subreaper) {
struct task_struct *reaper;
_
Subject: Subject: pidns: find_new_reaper() can no longer switch to init_pid_ns.child_reaper
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
linux-next.patch
mm-correctly-synchronize-rss-counters-at-exit-exec.patch
kmod-avoid-deadlock-from-recursive-kmod-call.patch
pidns-guarantee-that-the-pidns-init-will-be-the-last-pidns-process-reaped.patch
pidns-find_new_reaper-can-no-longer-switch-to-init_pid_nschild_reaper.patch
c-r-fcntl-add-f_getowner_uids-option.patch
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