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    SubjectRe: [PATCH] Make agpsupport work with modversions
    Date
    On Thu, 19 Oct 2000 01:56:38 +0100 (BST), 
    Alan Cox <alan@lxorguk.ukuu.org.uk> wrote:
    >Keith Owens wrote
    >> modprobe would attempt to satisfy weak external references as if they
    >> were normal references, including all the module dependency chains and
    >> reference counts. If the reference cannot be satisfied, it is set to
    >> zero instead of causing an error. No changes to load/unload.
    >
    >I dont believe modprobe can do this race free in userspace

    Module dependency checking in userspace has always been racy. A is
    being loaded and needs a symbol from B. B was loaded at the start of
    insmod so the symbol was resolved. By the time A is actually loaded, B
    has been removed, userspace race. This is checked for in
    sys_init_module()

    printk(KERN_ERR "init_module: found dependency that is "
    "(no longer?) a module.\n");

    Making some of the external references weak makes no difference.
    Either they are resolved to a module by insmod and checked by
    sys_init_module() or insmod replaces the reference with NULL.

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