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    SubjectRe: [RFC patch 2/3] tree/tiny rcu: Add debug RCU head objects (v3)
    On Fri, Mar 19, 2010 at 04:47:41PM -0400, Mathieu Desnoyers wrote:
    > Helps finding racy users of call_rcu(), which results in hangs because list
    > entries are overwritten and/or skipped.
    > This new patch version is based on the debugobjects with the newly introduced
    > "active state" tracker.
    > Non-initialized entries are all considered as "statically initialized". An
    > activation fixup (triggered by call_rcu()) takes care of performing the debug
    > object initialization without issuing any warning. Since we cannot increase the
    > size of struct rcu_head, I don't see much room to put an identifier for
    > statically initialized rcu_head structures. So for now, we have to live without
    > "activation without explicit init" detection. But the main purpose of this debug
    > option is to detect double-activations (double call_rcu() use of a rcu_head
    > before the callback is executed), which is correctly addressed here.
    > This also detects potential internal RCU callback corruption, which would cause
    > the callbacks to be executed twice.

    Is this useful?

    Basic usage is so there no double call_rcu():

    if (atomic_dec_and_test())

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      Last update: 2010-03-19 23:13    [W:0.020 / U:16.304 seconds]
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