On Mon, May 04, 2015 at 03:00:44PM -0400, Rik van Riel wrote: In case of the non-preemptible RCU, we could easily also > increase current->rcu_read_lock_nesting at the same time > we increase the preempt counter, and use that as the > indicator to test whether the cpu is in an extended > rcu quiescent state. That way there would be no extra > overhead at syscall entry or exit at all. The trick > would be getting the preempt count and the rcu read > lock nesting count in the same cache line for each task.
Can't do that. Remember, on x86 we have per-cpu preempt count, and your rcu_read_lock_nesting is per task. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
