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    SubjectRe: Question on lockdep and MAX_LOCK_DEPTH
    On 02/05/2013 05:54 PM, Steven Rostedt wrote:

    > I'm not sure the swapper task is part of the 'do_each_thread()' loop.
    >
    > Perhaps what you want to do is add a:
    >
    > lockdep_print_held_locks(current);

    I'll add that and test...

    > I'm curious. Does your code grab a read lock? If you grab the same read
    > lock multiple times it adds to the list each time. Thus if you have
    > anything like:
    >
    > for (i = 0; i < 100; i++ ) {
    > read_lock(&lock);
    > }
    >
    > for (i = 0; i < 100; i++) {
    > read_unlock(&lock);
    > }
    >
    > That will fill up the held locks quite a bit.
    >
    > The above code I showed is ridiculous and I doubt you have it, but if
    > you have something that does lots of recursive reads for some reason,
    > that could be an issue.

    I have only one read/write lock in my module, and it looks like
    I always lock it as a writer (will fix that soon for performance
    reasons, but it should be valid locking I think).

    I have no rcu locks at all in my module currently.

    I've seen similar lockups on another machine that does not use
    this module, but it uses a hacked up pktgen. I haven't found
    a test case that reproduces this on a clean upstream build,
    but I am still fairly suspicious that it isn't my code.
    Famous last words I'm sure :)

    Thanks,
    Ben

    --
    Ben Greear <greearb@candelatech.com>
    Candela Technologies Inc http://www.candelatech.com



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