Attach my own pid

[Nitin Varyani]

rather this will also suffice

if (* pid == NULL*) {
                 retval = -ENOMEM;
                 pid = alloc_pid(p->nsproxy->pid_ns);
                 if (!pid)
                         goto bad_fork_cleanup_io;
         }

         p->pid = pid_nr(pid);

On Sun, Mar 27, 2016 at 4:57 PM, Nitin Varyani <varyani.nitin1 at gmail.com>
wrote:

> If I do the following thing:
>
> struct pid remote_struct_pid;
> remote_struct_pid.numbers[0].nr=*my_pid*;
> p = copy_process(clone_flags, stack_start, stack_size, child_tidptr,
> *remote_struct_pid*, trace, tls);
>
> and modify the copy_process function little bit (marked in BOLD), it may
> serve my objective.
>
> if (pid != &init_struct_pid *&& pid == NULL*) {
>                  retval = -ENOMEM;
>                  pid = alloc_pid(p->nsproxy->pid_ns);
>                  if (!pid)
>                          goto bad_fork_cleanup_io;
>          }
>
>          p->pid = pid_nr(pid);
>
> The pids by kernel are allocated in the range (RESERVED_PIDS,
> PID_MAX_DEFAULT) and I will choose *my_pid* outside this range.
> I will have to modify system calls/kernel to cater to such processes.
>
>
> On Tue, Mar 22, 2016 at 3:55 PM, Bernd Petrovitsch <
> bernd at petrovitsch.priv.at> wrote:
>
>> On Die, 2016-03-22 at 01:26 -0400, Valdis.Kletnieks at vt.edu wrote:
>> > On Mon, 21 Mar 2016 16:01:41 +0530, Nitin Varyani said:
>> >
>> > > I am running a master user-level process at Computer 1 which sends a
>> > > process context like code, data, registers, PC, etc as well as
>> *"pid"* to
>> > > slave processes running at other computers. The responsibility of the
>> slave
>> > > process is to fork a new process on order of master process and
>> attach *"pid"
>> > > *given by the master to the new process it has forked. Any system
>> call on
>> > > slave nodes will have an initial check of " Whether the process
>> belongs to
>> > > local node or to the master node?". That is, if kernel at Computer 2
>> pid of
>> > > the process is 1500
>> >
>> > None of that requires actually controlling the PID of the child.
>>
>> Well, I think that the OP wants to map the PIDs with a fixed offset per
>> host. So e.g. the local PID == 14 becomes 20014 on all other nodes.
>> At least for debugging it's easier than some random mappings;-)
>>
>> As for top post: TTBOMK there is no SysCall for doing that.
>> * Perhaps one can achieve something similar with containers - one
>>   container per remote host or so (but I never used containers actively
>>   myself) or (ab)use KVM (does vServer still live?) for local
>>   "pseudo-VMs" (and use there the original PIDs - or so).
>> * The manual page of clone(2) doesn't reveal to me if it's possible to
>>   wish for a PID.
>> * You could clone (pun not intended;-) the fork() syscall and add an
>>   parameter - the PID - to it (and e.g. return -1 if it's already used).
>>
>> BTW I don't know how the rest of the kernel reacts to such artifical
>> PIDs (but you will see;-) outside the "official range".
>>
>> MfG,
>>         Bernd
>> --
>> "What happens when you read some doc and either it doesn't answer your
>> question or is demonstrably wrong? In Linux, you say "Linux sucks" and
>> go read the code. In Windows/Oracle/etc you say "Windows sucks" and
>> start banging your head against the wall."    - Denis Vlasenko on lkml
>>
>>
>>
>
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