rcu: fine-tune grace-period begin/end checks
Use the CPU's bit in rnp->qsmask to determine whether or not the CPU should try to report a quiescent state. Handle overflow in the check for rdp->gpnum having fallen behind. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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@ -617,9 +617,17 @@ static void __init check_cpu_stall_init(void)
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static void __note_new_gpnum(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp)
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{
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if (rdp->gpnum != rnp->gpnum) {
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/*
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* If the current grace period is waiting for this CPU,
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* set up to detect a quiescent state, otherwise don't
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* go looking for one.
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*/
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rdp->gpnum = rnp->gpnum;
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if (rnp->qsmask & rdp->grpmask) {
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rdp->qs_pending = 1;
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rdp->passed_quiesc = 0;
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rdp->gpnum = rnp->gpnum;
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} else
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rdp->qs_pending = 0;
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}
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}
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@ -681,19 +689,20 @@ __rcu_process_gp_end(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_dat
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/*
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* If we were in an extended quiescent state, we may have
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* missed some grace periods that others CPUs took care on
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* missed some grace periods that others CPUs handled on
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* our behalf. Catch up with this state to avoid noting
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* spurious new grace periods.
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* spurious new grace periods. If another grace period
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* has started, then rnp->gpnum will have advanced, so
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* we will detect this later on.
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*/
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if (rdp->completed > rdp->gpnum)
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if (ULONG_CMP_LT(rdp->gpnum, rdp->completed))
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rdp->gpnum = rdp->completed;
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/*
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* If another CPU handled our extended quiescent states and
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* we have no more grace period to complete yet, then stop
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* chasing quiescent states.
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* If RCU does not need a quiescent state from this CPU,
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* then make sure that this CPU doesn't go looking for one.
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*/
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if (rdp->completed == rnp->gpnum)
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if ((rnp->qsmask & rdp->grpmask) == 0)
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rdp->qs_pending = 0;
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}
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}
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