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    SubjectRe: x86_pmu_start WARN_ON.
    On Tue, 18 Feb 2014, Vince Weaver wrote:

    > On Mon, 17 Feb 2014, Peter Zijlstra wrote:
    >
    > > Enable CONFIG_FRAME_POINTER for better stack traces; I suspect the
    > > list_del_event() is just random stack garbage. The path that makes sense
    > > is:
    > > wait_rcu()->__wait_for_common()->schedule_timeout()
    >
    > Here's an updated stack trace on 3.14-rc3 with CONFIG_FRAME_POINTER
    > enabled, in case it's helpful:

    Still chasing this, although all I can add are these debug messages:

    [ 140.812003] PROBLEM: n_events=2 n_added=2 VMW: idx=33 state=f00 type=0 config=0 samp_per=5e6069eb0
    [ 140.812003] ALL: VMW: Num=0 idx=33 state=f00 type=0 config=0 samp_per=5e6069eb0
    [ 140.812003] ALL: VMW: Num=1 idx=0 state=3 type=0 config=1 samp_per=0

    So when the WARN gets triggered there only only two events in the event
    list, the NMI watchdog which has already been enabled somehow (that f00
    I stuck in, pmu_start sets it to f00 instead of 00 to make sure it wasn't
    something stomping on memory) and the precise instructions event.

    I still have a hard time following what all the schedule in code is doing.

    Vince


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