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rcu: Abstract the dynticks snapshot operation
This commit is the second step towards full abstraction of all accesses to the ->dynticks counter, implementing the previously open-coded atomic add of zero in a new rcu_dynticks_snap() function. This abstraction will ease changes o the ->dynticks counter operation. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
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parent
6563de9d6f
commit
8b2f63ab05
2 changed files with 18 additions and 7 deletions
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@ -281,6 +281,17 @@ static DEFINE_PER_CPU(struct rcu_dynticks, rcu_dynticks) = {
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#endif /* #ifdef CONFIG_NO_HZ_FULL_SYSIDLE */
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};
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/*
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* Snapshot the ->dynticks counter with full ordering so as to allow
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* stable comparison of this counter with past and future snapshots.
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*/
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static int rcu_dynticks_snap(struct rcu_dynticks *rdtp)
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{
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int snap = atomic_add_return(0, &rdtp->dynticks);
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return snap;
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}
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/*
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* Do a double-increment of the ->dynticks counter to emulate a
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* momentary idle-CPU quiescent state.
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@ -1049,7 +1060,9 @@ void rcu_nmi_exit(void)
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*/
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bool notrace __rcu_is_watching(void)
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{
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return atomic_read(this_cpu_ptr(&rcu_dynticks.dynticks)) & 0x1;
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struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
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return atomic_read(&rdtp->dynticks) & 0x1;
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}
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/**
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@ -1132,7 +1145,7 @@ static int rcu_is_cpu_rrupt_from_idle(void)
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static int dyntick_save_progress_counter(struct rcu_data *rdp,
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bool *isidle, unsigned long *maxj)
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{
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rdp->dynticks_snap = atomic_add_return(0, &rdp->dynticks->dynticks);
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rdp->dynticks_snap = rcu_dynticks_snap(rdp->dynticks);
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rcu_sysidle_check_cpu(rdp, isidle, maxj);
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if ((rdp->dynticks_snap & 0x1) == 0) {
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trace_rcu_fqs(rdp->rsp->name, rdp->gpnum, rdp->cpu, TPS("dti"));
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@ -1157,7 +1170,7 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp,
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int *rcrmp;
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unsigned int snap;
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curr = (unsigned int)atomic_add_return(0, &rdp->dynticks->dynticks);
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curr = (unsigned int)rcu_dynticks_snap(rdp->dynticks);
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snap = (unsigned int)rdp->dynticks_snap;
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/*
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@ -356,10 +356,9 @@ static void sync_rcu_exp_select_cpus(struct rcu_state *rsp,
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mask_ofl_test = 0;
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for_each_leaf_node_possible_cpu(rnp, cpu) {
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struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
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struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
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rdp->exp_dynticks_snap =
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atomic_add_return(0, &rdtp->dynticks);
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rcu_dynticks_snap(rdp->dynticks);
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if (raw_smp_processor_id() == cpu ||
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!(rdp->exp_dynticks_snap & 0x1) ||
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!(rnp->qsmaskinitnext & rdp->grpmask))
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@ -380,12 +379,11 @@ static void sync_rcu_exp_select_cpus(struct rcu_state *rsp,
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for_each_leaf_node_possible_cpu(rnp, cpu) {
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unsigned long mask = leaf_node_cpu_bit(rnp, cpu);
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struct rcu_data *rdp = per_cpu_ptr(rsp->rda, cpu);
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struct rcu_dynticks *rdtp = &per_cpu(rcu_dynticks, cpu);
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if (!(mask_ofl_ipi & mask))
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continue;
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retry_ipi:
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if (atomic_add_return(0, &rdtp->dynticks) !=
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if (rcu_dynticks_snap(rdp->dynticks) !=
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rdp->exp_dynticks_snap) {
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mask_ofl_test |= mask;
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continue;
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