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    SubjectRe: [PATCH tip/core/urgent] fix several lockdep splats, allow multiple splats
    On Fri, Apr 30, 2010 at 12:16:45PM -0400, Valdis.Kletnieks@vt.edu wrote:
    > On Fri, 30 Apr 2010 11:33:34 EDT, Mathieu Desnoyers said:
    >
    > > I recommend creating a kernel command line parameter that would tweak
    > > the number of messages printed by lockdep. The default would indeed by 1
    > > message, but people in a debugging marathon can specify a larger value
    > > so they won't have to reboot between each individual lockdep error.
    >
    > Yeah, that would rock for development kernels - playing whack-a-mole with
    > a half-dozen new lockdep whinges can easily stretch out for quite some time.

    The RCU-lockdep splats are a bit different in nature than the
    deadlock-related splats that lockdep normally prints. The RCU-lockdep
    splats are transient in nature, and it is easy to apply WARN_ON_ONCE().
    In contrast, if you permit multiple deadlock-related lockdep splats,
    you tend to get lots of warnings about the same deadlock cycle.

    So how about an additional kernel configuration variable, default
    disabled, perhaps named CONFIG_PROVE_RCU_MULTIPLE, that allows a
    single boot to see multiple messages? Unlike the dyntick-idle
    WARN_ON()s that generated multi-gigabyte console logs in a great
    hurry, I haven't yet seen excessive quantities of RCU-lockdep splats,
    so I don't see the need for an integer limit.

    Thoughts?

    Thanx, Paul


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