On Thu, 2011-04-28 at 09:41 -0500, Serge Hallyn wrote:
> Quoting Ulli Horlacher (frams...@rus.uni-stuttgart.de):
> >
> > Is there a way to get the corresponding host PID for a container PID?
> >
> > For example: inside the the container the process "init" has always PID 1.
> > But what PID has this process in the host process table?
> >
> > ps aux | grep ... is not what I am looking for, I want more robust solution.
>
> There is nothing that gives you a 100% guaranteed correct race-free
> correspondence right now. You can look under /proc/<pid>/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/<pid> inode numbers since they are different
> filesystems for each proc mount.
>
> It's tempting to say that we should put a per-task unique id under
> /proc/<pid> for each task. However that would likely be nacked because
> it introduces a new namespace of its own.
>
An alternative could be to expose the container pid
in /proc/<pid>/status. Could such a patch make it to mainline ?
--- a/fs/proc/array.c
+++ b/fs/proc/array.c
@@ -337,6 +337,12 @@ static void task_cpus_allowed(struct seq_file *m,
struct task_struct *task)
seq_putc(m, '\n');
}
+static void task_vpid(struct seq_file *m, struct task_struct *task)
+{
+ struct pid_namespace *ns = task_active_pid_ns(task);
+ seq_printf(m, "Vpid:\t%d\n", ns ? task_pid_nr_ns(task, ns) : 0);
+}
+
int proc_pid_status(struct seq_file *m, struct pid_namespace *ns,
struct pid *pid, struct task_struct *task)
{
@@ -354,6 +360,7 @@ int proc_pid_status(struct seq_file *m, struct
pid_namespace *ns,
task_cpus_allowed(m, task);
cpuset_task_status_allowed(m, task);
task_context_switch_counts(m, task);
+ task_vpid(m, task);
return 0;
}
Signed-off-by: Greg Kurz <gk...@fr.ibm.com>
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