Commit e05121ba authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

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: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent 17a8212b

include/trace/events/rcu.h

+5 −5
Original line number Diff line number Diff line
@@ -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,

kernel/rcu/tree.c

+1 −8
Original line number Diff line number Diff line
@@ -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);

kernel/rcu/tree.h

+0 −1
Original line number Diff line number Diff line
@@ -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(). */

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