From e05121ba5b81e2f85349f038642410578457f6db Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 7 May 2018 12:07:48 -0700 Subject: [PATCH] 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 --- include/trace/events/rcu.h | 10 +++++----- kernel/rcu/tree.c | 9 +-------- kernel/rcu/tree.h | 1 - 3 files changed, 6 insertions(+), 14 deletions(-) diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h index 759e7e8..a8d07fe 100644 --- a/include/trace/events/rcu.h +++ b/include/trace/events/rcu.h @@ -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, diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 770f0df..5f1a11f 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -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); diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index 6683da6..795d469 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -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(). */ -- 2.7.4