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>

diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index 759e7e8..a8d07fe 100644 (file)
--- 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 (file)
--- 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 (file)
--- 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(). */