Messages in this thread | | | Date | Thu, 10 Sep 2009 09:31:40 -0700 | From | Sukadev Bhattiprolu <> | Subject | Re: [RFC][v6][PATCH 9/9]: Document clone_with_pids() syscall |
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Thanks for the review. Will fix the typos.
Randy Dunlap [randy.dunlap@oracle.com] wrote: | > +Example: | > + | > + struct pid_set pid_set { 3, {0, 99, 177} }; | > + void *child_stack = malloc(STACKSIZE); | > + | > + /* set up child_stack, like with clone() */ | > + rc = clone_with_pids(clone_flags, child_stack, NULL, NULL, &pid_set); | > + | > + if (rc < 0) { | > + perror("clone_with_pids()"); | > + exit(1); | > + } | | What happens when one of the pids is busy? Say the last one in the | example above [177]. Are the first 2 children already cloned | or are all pids checked for availability before cloning?
Only _one_ one child process is created (on success). With nested pid namespaces a process is known by different pids (or pid numbers to be precise) - one in each pid namespace.
(BTW, looks like we did not document pid-namespaces in the Documentation/ But please see the CLONE_NEWPID section of a recent version of clone(2)).
In short, the above clone_with_pids() tries to create a single child process with the given pids.
| If the latter, is there a race there? | and what value is returned?
There is no race - bc just a single process is being created.
If any of the pids are not available, the child process is not created and the system call returns -EBUSY (if the user requested say 99 and 99 is in use by another process)
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