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 Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ 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 -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html