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rcu: Remove CPU-hotplug failsafe from force-quiescent-state code path 

Now that quiescent states for newly offlined CPUs are reported either
when that CPU goes offline or at the end of grace-period initialization,
the CPU-hotplug failsafe in the force-quiescent-state code path is no
longer needed.

This commit therefore removes this failsafe.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2018-05-07 12:07:48 -07:00
parent 17a8212b8d
commit e05121ba5b
3 changed files with 6 additions and 14 deletions
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10
include/trace/events/rcu.h
View File

@ -391,11 +391,11 @@ TRACE_EVENT(rcu_quiescent_state_report,
/*
* Tracepoint for quiescent states detected by force_quiescent_state().
* These trace events include the type of RCU, the grace-period number that
* was blocked by the CPU, the CPU itself, and the type of quiescent state,
* which can be "dti" for dyntick-idle mode, "ofl" for CPU offline, "kick"
* when kicking a CPU that has been in dyntick-idle mode for too long, or
* "rqc" if the CPU got a quiescent state via its rcu_qs_ctr.
* These trace events include the type of RCU, the grace-period number
* that was blocked by the CPU, the CPU itself, and the type of quiescent
* state, which can be "dti" for dyntick-idle mode, "kick" when kicking
* a CPU that has been in dyntick-idle mode for too long, or "rqc" if the
* CPU got a quiescent state via its rcu_qs_ctr.
*/
TRACE_EVENT(rcu_fqs,

9
kernel/rcu/tree.c
View File

@ -1188,14 +1188,6 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp)
smp_store_release(ruqp, true);
}
/* Check for the CPU being offline. */
if (!(rdp->grpmask & rcu_rnp_online_cpus(rnp))) {
trace_rcu_fqs(rdp->rsp->name, rdp->gp_seq, rdp->cpu, TPS("ofl"));
rdp->offline_fqs++;
rcu_gpnum_ovf(rnp, rdp);
return 1;
}
/*
* A CPU running for an extended time within the kernel can
* delay RCU grace periods. When the CPU is in NO_HZ_FULL mode,
@ -3718,6 +3710,7 @@ void rcu_cpu_starting(unsigned int cpu)
nbits = bitmap_weight(&oldmask, BITS_PER_LONG);
/* Allow lockless access for expedited grace periods. */
smp_store_release(&rsp->ncpus, rsp->ncpus + nbits); /* ^^^ */
rcu_gpnum_ovf(rnp, rdp); /* Offline-induced counter wrap? */
if (rnp->qsmask & mask) { /* RCU waiting on incoming CPU? */
/* Report QS -after- changing ->qsmaskinitnext! */
rcu_report_qs_rnp(mask, rsp, rnp, rnp->gp_seq, flags);

1
kernel/rcu/tree.h
View File

@ -217,7 +217,6 @@ struct rcu_data {
/* 4) reasons this CPU needed to be kicked by force_quiescent_state */
unsigned long dynticks_fqs; /* Kicked due to dynticks idle. */
unsigned long offline_fqs; /* Kicked due to being offline. */
unsigned long cond_resched_completed;
/* Grace period that needs help */
/* from cond_resched(). */