Quoting Hu Tao (hutao@xxxxxxxxxxxxxx): > Hi, > > On Fri, Jul 25, 2014 at 05:34:43PM +0000, Serge Hallyn wrote: > > Quoting chenhanxiao@xxxxxxxxxxxxxx (chenhanxiao@xxxxxxxxxxxxxx): > > > Hi, > > > > > > > -----Original Message----- > > > > From: Serge Hallyn [mailto:serge.hallyn@xxxxxxxxxx] > > > > Sent: Tuesday, July 15, 2014 12:16 PM > > > > To: Chen, Hanxiao/陈 晗霄 > > > > Subject: Re: [RFC]Pid conversion between pid namespace > > > > > A-2) syscall pid_t getnspid(pid_t query_pid, pid_t observer_pid) > > > > > pros: > > > > > - ns procfs free, easy to use. > > > > > We could get rid of mounted ns procfs. > > > > > > > > > > cons: > > > > > - may find multiple results in nested ns. > > > > > We wished the new API could tell us the exact answer. > > > > > But if getnspid return more than one results will bring trouble to admins, > > > > > > > > (See below for more, but) the question being posed to getnspid has precisely > > > > one answer. > > > > > > > > > they had to make another decision. > > > > > Or we marked the deepest level for translation as prerequisite. > > > > > > > > > > -based on current pidns, no reference ns. > > > > > > > > Hm, no. The intent here was that > > > > > > > > observer_pid would be in current ns > > > > query_pid would be in observer_pid's ns. > > > > > > > > So this would be ideal for "I got a pid in a logfile created by rsyslog in > > > > a nested contaner, what is the logged pid in my pidns." > > > > > > > > Taking a set of tasks (like a container with nesting) and bulding a tree > > > > of all pids shouldn't be too difficult either. Start with the init pid, > > > > call getnspid($pid, $init_pid) for every $pid in the container; to figure > > > > out whether any $pid is itself a nested init_pid, we can compare the > > > > /proc/$$/ns/pid, as well as look at getnspid($pid, $pid). > > > I'm a little confused in this section: > > > > > > Ex: > > > init_pid_ns ns1 ns2 > > > t1 2 > > > t2 `- 3 1 > > > t3 `- 4 `- 5 1 > > > t4 `-6 `-8 `-9 > > > t5 `-10 `-9 `-10 > > > > > > For getnspid($pid, $init_pid), > > > Does init_pid means container's init_pid such as 3 for t2? > > > > Right, if you're in init_pid_ns and making the query, then > > you'd pass 3. > > Sorry for jumping in, but I'm not quite understanding the purpose of > $init_pid here, does it identify the ns which the process to be > queried is in? Also see my questions below: I was passing in initpid for a particular reason before, the second argument is NOT meant to be an "initpid", it's meant to be the pid (in caller's ns) of the observer pid - the pid in whose namespace we are querying. > 1. Given the example above, what's the return of getnspid(9, 3)? > Is it 6(task t4) or 10(task t5)? Assuming the caller is in init_pid_ns, then the return value is t5. > > 2. if there is a process in ns1 which is a child of process 1 has pid > 10, but not in ns2, like below: > > init_pid_ns ns1 ns2 > t1 2 > t2 `- 3 1 > t3 `- 4 +- 5 1 > t4 `-6 | `-8 `-9 > t5 `-10 | `-9 `-10 > t6 `-11 `-10 > > then what is the return of getnspid(10, 3)? Assuming the caller is in init_pid_ns, the answer is t6. The question was "In the pid_ns belonging to t2 (pid 3), what task does the pid 10 refer to". _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/containers
