Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755626Ab1FOO4G (ORCPT ); Wed, 15 Jun 2011 10:56:06 -0400 Received: from mtagate4.uk.ibm.com ([194.196.100.164]:39709 "EHLO mtagate4.uk.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754735Ab1FOO4D (ORCPT ); Wed, 15 Jun 2011 10:56:03 -0400 From: Greg Kurz Subject: [PATCH] Introduce ActivePid: in /proc/self/status (v2, was Vpid:) To: akpm@linux-foundation.org Cc: containers@lists.osdl.org, linux-kernel@vger.kernel.org, serge@hallyn.com, daniel.lezcano@free.fr, ebiederm@xmission.com, oleg@redhat.com, xemul@openvz.org Date: Wed, 15 Jun 2011 16:55:27 +0200 Message-ID: <20110615145527.4016.70157.stgit@bahia.local> User-Agent: StGIT/0.14.3 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 3269 Lines: 92 Since pid namespaces were introduced, there's a recurring demand: how one can correlate a pid from a child pid ns with a pid from a parent pid ns ? The need arises in the LXC community when one wants to send a signal from the host (aka. init_pid_ns context) to a container process for which one only knows the pid inside the container. In the future, this should be achievable thanks to Eric Biederman's setns() syscall but there's still some work to be done to support pid namespaces: https://lkml.org/lkml/2011/5/21/162 As stated by Serge Hallyn in: http://sourceforge.net/mailarchive/message.php?msg_id=27424447 "There is nothing that gives you a 100% guaranteed correct race-free correspondence right now. You can look under /proc//root/proc/ to see the pids valid in the container, and you can relate output of lxc-ps --forest to ps --forest output. But nothing under /proc that I know of tells you "this task is the same as that task". You can't even look at /proc/ inode numbers since they are different filesystems for each proc mount." This patch adds a single line to /proc/self/status. Provided one has kept track of its container tasks (with a cgroup like liblxc does for example), he may correlate global pids and container pids. This is still racy but definitely easier than what we have today. ChangeLog: v2: - changed Vpid: to ActivePid: - lock ->sighand before calling task_active_pid_ns() Signed-off-by: Greg Kurz Signed-off-by: Cedric Le Goater --- fs/proc/array.c | 17 +++++++++++++++-- 1 files changed, 15 insertions(+), 2 deletions(-) diff --git a/fs/proc/array.c b/fs/proc/array.c index 5e4f776..5f796d9 100644 --- a/fs/proc/array.c +++ b/fs/proc/array.c @@ -165,7 +165,8 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns, int g; struct fdtable *fdt = NULL; const struct cred *cred; - pid_t ppid, tpid; + pid_t ppid, tpid, actpid; + struct sighand_struct *sighand; rcu_read_lock(); ppid = pid_alive(p) ? @@ -176,6 +177,17 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns, if (tracer) tpid = task_pid_nr_ns(tracer, ns); } + actpid = 0; + sighand = rcu_dereference(p->sighand); + if (sighand) { + struct pid_namespace *pid_ns; + unsigned long flags; + spin_lock_irqsave(&sighand->siglock, flags); + pid_ns = task_active_pid_ns(p); + if (pid_ns) + actpid = task_pid_nr_ns(p, pid_ns); + spin_unlock_irqrestore(&sighand->siglock, flags); + } cred = get_task_cred(p); seq_printf(m, "State:\t%s\n" @@ -183,12 +195,13 @@ static inline void task_state(struct seq_file *m, struct pid_namespace *ns, "Pid:\t%d\n" "PPid:\t%d\n" "TracerPid:\t%d\n" + "ActivePid:\t%d\n" "Uid:\t%d\t%d\t%d\t%d\n" "Gid:\t%d\t%d\t%d\t%d\n", get_task_state(p), task_tgid_nr_ns(p, ns), pid_nr_ns(pid, ns), - ppid, tpid, + ppid, tpid, actpid, cred->uid, cred->euid, cred->suid, cred->fsuid, cred->gid, cred->egid, cred->sgid, cred->fsgid); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/