On 01/04/2011 08:57 PM, Mike Heffner wrote: > On 01/04/2011 11:04 AM, Daniel Lezcano wrote: >> On 01/04/2011 12:02 AM, Mike Heffner wrote: >>> Hi, >>> >>> Is it possible for a process running in a parent PID namespace to map >>> the PID of a process running in a child's namespace from the >>> parent->child's namespace? For example, if I span the process "myproc" >>> with CLONE_NEWPID then a call to getpid() inside myproc will return "1" >>> whereas in the parent's namespace that process could actually be PID >>> "23495". I'd like to be able to know that 23495 maps to 1 in the new >>> NS. >>> Obviously, just mapping the first PID is straightforward since I can >>> just look at the result of clone(). However, mapping the PIDs of >>> processes subsequently forked from "myproc" -- in this example -- I >>> haven't been able to figure out. >> >> AFAIK, it is not possible. >> >> That would be very nice to show the pid<-> vpid association. >> >> The procfs is a good candidate to show these informations. >> >> That would makes sense to show the content of /proc/<pid>/status with >> the pid relatively to the namespace. >> >> Let me give an example: >> >> Assuming the process '1234' creates a new pid namespace, and the child >> which is '1' in the new namespace has the real pid '4321'. This one >> mounts its /proc. >> >> If the process '1234' looks at /proc/4321/root/proc/1/status, it sees: >> >> ... >> Tgid: 1 >> Pid: 1 >> PPid: 0 >> ... >> >> >> It could be: >> >> ... >> Tgid: 4321 >> Pid: 4321 >> PPid: 1234 >> ... >> >> as the file is inspected from the parent namespace. Of course, if the >> file is looked from the child namespace context, we will see '1', '1' >> and '0'. >> >> I suppose the patch in the kernel should very small also. >> >> Thoughts ? > > Would that mean that finding the pid->vpid association for a real PID > X requires checking all files /proc/<X>/root/proc/<Y>/status where Y > is all vpids until you find the one where Pid == X? It would be nice > to have a have a way to check a single file for the association where > vpid is not known beforehand -- unless I'm misunderstanding your > solution. Hmm, right. But how do you know a pid is belonging to a specific pid namespace ? I mean you can have a single process creating several pid namespaces. So while looking at the /proc/<pid>/status, you can see several times the same vpid, no ? I am not sure the kind of informations you want to collect but it is not really a problem to build an association table from the userspace by browsing the /proc/<pid>/root/proc/<vpids> and their corresponding pid from the 'status' file information. Do you have an example for a pid -> vpid association without looking at more informations from /proc ? _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers
