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Date: Sat, 22 Jul 2006 11:29:34 -0400 From: Mathieu Desnoyers <compudj@...stal.dyndns.org> To: "Paul E. McKenney" <pmckenne@...ibm.com> Cc: Bill Huey <bhuey@...w.com>, linux-kernel@...r.kernel.org Subject: NMI reentrant RCU list for -rt kernels Hi Paul, Following your presentation on RCU lists for -rt kernel, discussing with Bill Huey led me to the following idea that could solve the problem of NMI reentrancy of RCU read side in the -rt kernels. If we consider that the RCU list modification that makes the read side lock preemptible is only needed for very long code paths, we could leave the original RCU implementation along with the preemptible one, so that very short and frequent code paths could benefit of using the very cheap preempt count protection without having a too big impact on the scheduler latency. For instance, my LTTng tracer disables the preemption for about 95 ns, which I doubt would be a problem for real-time behavior. I could easily fix maximum a maximum list size so it can be run in a constant time. So, basically, the idea is to have two RCU API that could take names like : atomic_rcu_* and rcu_* Does this idea make sense ? Mathieu OpenPGP public key: http://krystal.dyndns.org:8080/key/compudj.gpg Key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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