Messages in this thread | | | Date | Wed, 30 Apr 2014 11:14:25 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2] rwsem: Support optimistic spinning |
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On Mon, Apr 28, 2014 at 03:09:01PM -0700, Davidlohr Bueso wrote: > +static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem) > +{ > + int retval; > + struct task_struct *owner; > + > + rcu_read_lock(); > + owner = ACCESS_ONCE(sem->owner); > + > + /* Spin only if active writer running */ > + if (owner) > + retval = owner->on_cpu; > + else { > + /* > + * When the owner is not set, the sem owner may have just > + * acquired it and not set the owner yet, or the sem has > + * been released, or reader active. > + */ > + retval = false; > + } > + rcu_read_unlock(); > + > + return retval; > +}
Also, the mutex case has a need_resched() test in there; any particular reason you didn't mirror that?
See 46af29e479cc0 ("locking/mutexes: Return false if task need_resched() in mutex_can_spin_on_owner()")
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