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    SubjectRe: [patch 2/4] tree rcu: Add debug RCU head option
    Mathieu Desnoyers a écrit :
    > * Eric Dumazet (eric.dumazet@gmail.com) wrote:
    >> Mathieu Desnoyers a écrit :
    >>> Poisoning the rcu_head callback list. Only for rcu tree for now.
    >>>
    >>> Helps finding racy users of call_rcu(), which results in hangs because list
    >>> entries are overwritten and/or skipped. Using the lower bit to poison because
    >>> include/net/dst.h __pad_to_align_refcnt complains when struct rcu_head grows.
    >>>
    >> I see :)
    >>
    >
    > I don't know if there is an easy fix for __pad_to_align_refcnt ?


    This check was added to make sure some tbench regression was not added if
    dst->__refcnt was moved around, I am sure you dont care about tbench being 10% slower,
    do you ?


    diff --git a/include/net/dst.h b/include/net/dst.h
    index 5a900dd..b8fba74 100644
    --- a/include/net/dst.h
    +++ b/include/net/dst.h
    @@ -154,7 +154,9 @@ static inline void dst_hold(struct dst_entry * dst)
    * If your kernel compilation stops here, please check
    * __pad_to_align_refcnt declaration in struct dst_entry
    */
    +#if !defined(DEBUG_RCU_HEAD)
    BUILD_BUG_ON(offsetof(struct dst_entry, __refcnt) & 63);
    +#endif
    atomic_inc(&dst->__refcnt);
    }

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