On Wed, May 22, 2013 at 02:50:31PM +0900, Simon Horman wrote: > This is intended for use in loops which read data protected by RCU and may > have a large number of iterations. Such an example is dumping the list of > connections known to IPVS: ip_vs_conn_array() and ip_vs_conn_seq_next(). > > The benefits are for CONFIG_PREEMPT_RCU=y where we save CPU cycles > by moving rcu_read_lock and rcu_read_unlock out of large loops > but still allowing the current task to be preempted after every > loop iteration for the CONFIG_PREEMPT_RCU=n case. > > The call to cond_resched() is not needed when CONFIG_PREEMPT_RCU=y. > Thanks to Paul E. McKenney for explaining this and for the > final version that checks the context with CONFIG_DEBUG_ATOMIC_SLEEP=y > for all possible configurations. > > The function can be empty in the CONFIG_PREEMPT_RCU case, > rcu_read_lock and rcu_read_unlock are not needed in this case > because the task can be preempted on indication from scheduler. > Thanks to Peter Zijlstra for catching this and for his help > in trying a solution that changes __might_sleep. > > Initial cond_resched_rcu_lock() function suggested by Eric Dumazet. Applied, thanks. -- To unsubscribe from this list: send the line "unsubscribe netfilter-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
