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    SubjectRe: [PATCH 1/4] SUNRPC: spin svc_rqst initialization to its own function
    On Fri, 18 Jan 2008 15:59:43 -0500
    "J. Bruce Fields" <bfields@fieldses.org> wrote:

    > On Mon, Jan 14, 2008 at 09:05:15AM -0500, Jeff Layton wrote:
    > > Move the initialzation in __svc_create_thread that happens prior to
    > > thread creation to a new function. Export the function to allow
    > > services to have better control over the svc_rqst structs.
    > >
    > > Also rearrange the rqstp initialization to prevent NULL pointer
    > > dereferences in svc_exit_thread in case allocations fail.
    >
    > Those NULL dereferences are from the
    >
    > list_del(&rqstp->rq_all);
    >
    > ? OK, make sense. Thanks!
    >
    > --b.
    >

    Sorry, I didn't explain that well...

    This was the problem that Neil pointed out with the existing code. If
    the rqstp kzalloc succeeds, but the later kmallocs in
    __svc_create_thread fail, we goto here:

    out_thread:
    svc_exit_thread(rqstp);

    svc_exit_thread does this:

    struct svc_pool *pool = rqstp->rq_pool;

    ...and then later:

    spin_lock_bh(&pool->sp_lock);

    ...but rq_pool is set after the kmallocs, so if they fail rq_pool will
    be NULL, and we'll oops in that spin_lock_bh().

    The fix is to move the kmallocs closer to the bottom in the new
    svc_prepare_thread function.

    Thanks,
    --
    Jeff Layton <jlayton@redhat.com>


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