Commit 2e4a7072 authored Oct 18, 2007 by Pavel Emelyanov Committed by Linus Torvalds Oct 19, 2007

pid namespaces: move exit_task_namespaces()



Make task release its namespaces after it has reparented all his children to
child_reaper, but before it notifies its parent about its death.

The reason to release namespaces after reparenting is that when task exits it
may send a signal to its parent (SIGCHLD), but if the parent has already
exited its namespaces there will be no way to decide what pid to dever to him
- parent can be from different namespace.

The reason to release namespace before notifying the parent it that when task
sends a SIGCHLD to parent it can call wait() on this taks and release it.  But
releasing the mnt namespace implies dropping of all the mounts in the mnt
namespace and NFS expects the task to have valid sighand pointer.

Thanks to Oleg for pointing out some races that can apear and helping with
patches and fixes.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Cc: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Sukadev Bhattiprolu <sukadev@us.ibm.com>
Cc: Paul Menage <menage@google.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

parent 762a24be

kernel/exit.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -774,6 +774,7 @@ static void exit_notify(struct task_struct *tsk)
		* jobs, send them a SIGHUP and then a SIGCONT. (POSIX 3.2.2.2)
		*/
		forget_original_parent(tsk);
		exit_task_namespaces(tsk);

		write_lock_irq(&tasklist_lock);
		/*
		@@ -984,7 +985,6 @@ fastcall NORET_TYPE void do_exit(long code)
		module_put(tsk->binfmt->module);

		proc_exit_connector(tsk);
		exit_task_namespaces(tsk);
		exit_notify(tsk);
		#ifdef CONFIG_NUMA
		mpol_free(tsk->mempolicy);

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