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    SubjectRe: [PATCH 1/5] Split wait_noreap_copyout()
    On 05/20, Ingo Molnar wrote:
    >
    > * Vitaly Mayatskikh <v.mayatskih@gmail.com> wrote:
    >
    > > 2. Fix copy_wait_opts_to_user to old behaviour by something like:
    > >
    > > if (!retval && (infop || WNOWAIT)) {
    > >
    > > What's your opinion?
    >
    > I'd suggest a variant of 2: keep this large-ish patch an equivalent
    > transformation - i.e. an impact: cleanup type of change.
    >
    > Then queue up a patch that removes this quirk.

    Yes, this would be the best option.

    The problem is, it is not trivial to keep the current behaviour and
    make the patch which looks like a cleanup, not uglification.

    copy_wait_opts_to_user() needs the new "called_from_wait_task_continued"
    argument, and it should do

    if (called_from_wait_task_continued && !wo->wo_info)
    return -EFAULT;

    Or we should add

    if (!infop && WNOWAIT)
    return -EFAULT;

    to all callers except wait_task_continued().


    Roland thinks that "-EFAULT -> success" change is acceptable, and I think
    the same. So, to me the best option is just change the changelog of this
    patch and that is all.

    Or. We can make a trivial patch which adds the behavior change first:

    Changelog: always accept the NULL infop, because it is not
    possible to understand the current behaviour ;)

    User-visible change! needs Acks!

    --- a/kernel/exit.c
    +++ b/kernel/exit.c
    @@ -1126,24 +1126,26 @@ static int eligible_child(struct wait_op
    static int wait_noreap_copyout(struct wait_opts *wo, struct task_struct *p,
    pid_t pid, uid_t uid, int why, int status)
    {
    - struct siginfo __user *infop;
    int retval = wo->wo_rusage
    ? getrusage(p, RUSAGE_BOTH, wo->wo_rusage) : 0;
    -
    put_task_struct(p);
    - infop = wo->wo_info;
    - if (!retval)
    - retval = put_user(SIGCHLD, &infop->si_signo);
    - if (!retval)
    - retval = put_user(0, &infop->si_errno);
    - if (!retval)
    - retval = put_user((short)why, &infop->si_code);
    - if (!retval)
    - retval = put_user(pid, &infop->si_pid);
    - if (!retval)
    - retval = put_user(uid, &infop->si_uid);
    - if (!retval)
    - retval = put_user(status, &infop->si_status);
    +
    + if (wo->wo_info) {
    + struct siginfo __user *infop = wo->wo_info;
    +
    + if (!retval)
    + retval = put_user(SIGCHLD, &infop->si_signo);
    + if (!retval)
    + retval = put_user(0, &infop->si_errno);
    + if (!retval)
    + retval = put_user((short)why, &infop->si_code);
    + if (!retval)
    + retval = put_user(pid, &infop->si_pid);
    + if (!retval)
    + retval = put_user(uid, &infop->si_uid);
    + if (!retval)
    + retval = put_user(status, &infop->si_status);
    + }
    if (!retval)
    retval = pid;
    return retval;

    And then redo Vitaly's patches on top of this change.

    What do you and Vitaly think?

    Oleg.



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