Messages in this thread | | | Date | Sun, 13 Jul 2008 23:13:15 +0200 | From | Ingo Molnar <> | Subject | Re: [PATCH]rcu classic: update qlen when cpu offline |
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* Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:
> On Thu, Jun 26, 2008 at 10:06:43AM +0800, Lai Jiangshan wrote: > > > > When callbacks are moved from offline cpu to this cpu, > > the qlen field of this rdp should be updated. > > Good catch!!! > > The effect of this bug would be for force_quiescent_state() to be invoked > when it should not and vice versa -- wasting cycles in the first case > and letting RCU callbacks remain piled up in the second case. The bug > is thus "benign" in that it does not result in premature grace-period > termination, but should of course be fixed nonetheless. > > Preemption is disabled by the caller's get_cpu_var(), so we are guaranteed > to remain on the same CPU, as required. The local_irq_disable() is indeed > needed, otherwise, an interrupt might invoke call_rcu() or call_rcu_bh(), > which could cause that interrupt's increment of ->qlen to be lost. > > So this patch looks correct to me. Good job, Jiangshan!!! > > Ingo, would you be willing to add this patch to tip/core/rcu? > > Reviewed-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
thanks, applied to tip/core/rcu. (sorry about the delay!)
Ingo
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