Messages in this thread | | | Date | Wed, 30 Apr 2014 11:04:20 +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;
And yet the return value is bool.
> + 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; > + }
And if you init the retval to false, you can leave this entire branch out.
> + rcu_read_unlock(); > + > + return retval; > +}
Which yields the much shorter:
static inline bool rwsem_can_spin_on_owner(struct rw_semaphore *sem) { struct task_struct *owner; bool on_cpu = false;
rcu_read_lock(); owner = ACCESS_ONCE(sem->owner); if (owner) on_cpu = owner->on_cpu; rcu_read_unlock();
return on_cpu; }
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