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    SubjectRe: safety of *mutex_unlock() (Was: [BUG] signal: sighand unprotected when accessed by /proc)
    On 06/11, Oleg Nesterov wrote:
    >
    > On 06/11, Paul E. McKenney wrote:
    >
    > > raw_spin_unlock_irqrestore(&rnp->lock, flags);
    > > rt_mutex_lock(&mtx); /* Side effect: boosts task t's priority. */
    > > rt_mutex_unlock(&mtx); /* Keep lockdep happy. */
    > >
    > > + /* Wait until boostee is done accessing mtx before reinitializing. */
    > > + wait_for_completion(&rnp->boost_completion);
    > > +
    >
    > I must have missed something, I dont understand why we need ->boost_completion.
    >
    > What if you simply move that rt_mutex into rcu_node ?
    >
    > Or. Given that rcu_boost_kthread() never exits, it can declare this mutex
    > on stack and pass the pointer to rcu_boost() ?

    Ah, please ignore, I forgot about init_proxy_locked(). Although perhaps this
    can be solved easily.

    Oleg.



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