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    SubjectRe: [BUG] NULL pointer deref with rcutorture
    hi,

    * Paul E. McKenney (paulmck@linux.vnet.ibm.com) wrote:
    > On Sun, Jan 04, 2009 at 03:57:26PM +0100, Eric Sesterhenn wrote:
    > >
    > > Just tell me what i need to do, I am not really familiar with ftrace.
    > > I am only able to test 2.6.28-04980-gb58602a, since current -git is not
    > > able to boot on this box :|
    >
    > Very cool!
    >
    > The idea is to have __call_rcu() in kernel/rcutree.c record the
    > address of the callback (argument "head") and the function (argument
    > "func"). In rcu_do_batch(), just before invoking list->func(list),
    > also record the address of the callback ("list") and the function
    > (again, "func").
    >
    > The new ftrace package has some mechanisms for doing this, but there is
    > always the old-fashioned way of using printk(), for example in
    > rcu_do_batch():
    >
    > prefetch(next);
    > if (rcu_dump_callbacks)
    > printk("rcu_head=%p, func=%p\n", list, func);
    > list->func(list);
    >
    > Initialize rcu_dump_callbacks to zero, then use a small kernel module
    > (or some such) to set it to one just before running your test.

    i did it via the ugly printk and captured it via netconsole

    for the box with rcutree you can find the log here:
    http://www.cccmz.de/~snakebyte/200.log
    The interesting part seems start at 155.858923, thats when I load
    the rcutorture module

    with http://www.cccmz.de/~snakebyte/200_1.log i had another try,
    actually saw a rcu_do_batch: rcu_head=d1907720, func=(null) in the traces,
    box went into unresponsive mode afterwards

    And just in case it helps somehow: http://www.cccmz.de/~snakebyte/200_3.log

    for the one with rcupreemt you can find the log here:
    http://www.cccmz.de/~snakebyte/201.log
    rcutorture is loaded at 87.312399

    Greetings, Eric


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