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    SubjectRe: [PATCH v8 3.2.0-rc5 1/9] uprobes: Install and remove breakpoints.
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    On Wed, 2012-01-04 at 17:51 +0100, Peter Zijlstra wrote:

    > > + if (is_register)
    > > + ret = install_breakpoint(mm, uprobe, vma, vi->vaddr);
    > > + else
    > > + remove_breakpoint(mm, uprobe, vi->vaddr);
    > > +
    > > + up_read(&mm->mmap_sem);
    > > + mmput(mm);
    > > + if (is_register) {
    > > + if (ret && ret == -EEXIST)
    > > + ret = 0;
    > > + if (ret)
    > > + break;
    > > + }
    >
    > Since you init ret := 0 and remove_breakpoint doesn't change it, this
    > conditional on is_register is superfluous.

    True, but I would argue that this is easier to understand. That is, we
    only break on a failed install_breakpoint (is_register is set). If I
    looked at this code and saw:

    if (is_register)
    ret = install_breakpoint()
    else
    remove_breakpoint()

    [...]

    if (ret && ret == -EEXIST)
    ret = 0;
    if (ret)
    break;

    I would first think that there might be a bug. That is, we should have a
    ret = remove_breakpoint().

    Thus, I would say, either leave this as is and hope gcc is smart enough
    to optimize out the if (is_register), or add the comment:

    /* ret will always be zero on remove_breakpoint */
    if (ret && ret == -EEXIST)
    ret = 0;
    if (ret)
    break;

    -- Steve

    >
    > > + }
    > > + list_for_each_entry_safe(vi, tmpvi, &try_list, probe_list) {
    > > + list_del(&vi->probe_list);
    > > + kfree(vi);
    > > + }
    > > + return ret;
    > > +}




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