Messages in this thread | | | Date | Wed, 21 Oct 2009 11:27:15 -0700 | From | Sukadev Bhattiprolu <> | Subject | Re: [RFC][v8][PATCH 10/10]: Document clone3() syscall |
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Pavel Machek [pavel@ucw.cz] wrote: | Hi! | | > This gives a brief overview of the clone3() system call. We should | | Thanks! | | > eventually describe more details in existing clone(2) man page or in | > a new man page. | | M. Kerrisk (see MAINTAINERS) maintains man pages...
Ok. I copied linux-api and M. Kerrisk is looking at this patchset.
| | > Changelog[v8]: | > - clone2() is already in use in IA64. Rename syscall to clone3() | ... | > Index: linux-2.6/Documentation/clone2 | > =================================================================== | > --- /dev/null 1970-01-01 00:00:00.000000000 +0000 | > +++ linux-2.6/Documentation/clone2 2009-10-12 19:54:38.000000000 -0700 | | clone3?
Ah, yes, will fix.
| | > +struct clone_struct { | > + u64 flags; | > + u64 child_stack; | | u64 seems wrong on 32 bit platforms. ulong? | | > + u32 nr_pids; | | So nr_pids is either 1 or 2?
No. With pid namespaces, which can be nested to arbitrary levels, each process has several pid numbers - one in its own namespace and one in each ancestor pid namespaces.
nr_pids specifies the number of pids the user cares about. IOW, if you checkpoint a process that is 3 levels below the init-pid-ns, and you care about the pids for those three levels, you would pass in an array of 4 pid_ts and nr_pids would be 4.
| | > + u32 reserved1; | > + u64 parent_tid; | > + u64 child_tid; | > + u64 reserved2; | > +}; | > + | | | > + See CLONE_NEWPID section of clone(2) man page for details about pid | > + namespaces. | > + | > + The order pids in @pids corresponds to the nesting order of pid- | > + namespaces, with @pids[0] corresponding to the init_pid_ns. | | Ok, so I'm confused.
Hope the above note on pid-namespaces helps, if not let me know.
| | > + If a pid in the @pids list is 0, the kernel will assign the next | > + available pid in the pid namespace, for the process. | > + | > + If a pid in the @pids list is non-zero, the kernel tries to assign | > + the specified pid in that namespace. If that pid is already in use | > + by another process, the system call fails with -EBUSY. | ... | > + On failure, clone3() returns -1 and sets 'errno' to one of following | > + values (the child process is not created). | | Inconsistent with above. Syscalls really return -ERRCODE, errno is | glibc magic.
Ok. Will make it consistent to say that it returns one of the error codes.
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