Hi Paul and everyone, I was tracing/studying the RCU code today in paul/dev branch and noticed that for dyntick-idle CPUs, the RCU GP thread is clearing the rnp->qsmask corresponding to the leaf node for the idle CPU, and reporting a QS on their behalf.
rcu_sched-10 [003] 40.008039: rcu_fqs: rcu_sched 792 0 dti rcu_sched-10 [003] 40.008039: rcu_fqs: rcu_sched 801 2 dti rcu_sched-10 [003] 40.008041: rcu_quiescent_state_report: rcu_sched 805 5>0 0 0 3 0 That's all good but I was wondering if we can do better for the idle CPUs if we can some how not set the qsmask of the node in the first place. Then no reporting would be needed of quiescent state is needed for idle CPUs right? And we would also not need to acquire the rnp lock I think. At least for a single node tree RCU system, it seems that would avoid needing to acquire the lock without complications. Anyway let me know your thoughts and happy to discuss this at the hallways of the LPC as well for folks attending :) thanks, - Joel