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    SubjectRe: [RFC][v8][PATCH 10/10]: Document clone3() syscall
    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...

    > 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?

    > +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?

    > + 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.

    > + 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.

    > +Example:
    > +
    > + pid_t pids[] = { 77, 99 };
    > + struct clone_struct cs;
    > +
    > + cs.flags = (u64) SIGCHLD;
    > + cs.child_stack = (u64) setup_child_stack();
    > + cs.nr_pids = 2;
    > + cs.parent_tid = 0LL;
    > + cs.child_tid = 0LL;
    > +
    > + rc = syscall(__NR_clone3, &cs, pids);

    Hmm, is there reason why pids are not at the end of struct
    clone_struct? Passing most parameters in special structure, then pids
    separately is strange...

    --
    (english) http://www.livejournal.com/~pavelmachek
    (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


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