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Commit 8aa670cd authored by Paul E. McKenney's avatar Paul E. McKenney
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rcu: Convert ->rcu_iw_gpnum to ->gp_seq 



This commit switches the interrupt-disabled detection mechanism to
->gp_seq.  This mechanism is used as part of RCU CPU stall warnings,
and detects cases where the stall is due to a CPU having interrupts
disabled.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent ba04107f

kernel/rcu/tree.c

+6 −6
Original line number Diff line number Diff line
@@ -1099,8 +1099,8 @@ static void rcu_gpnum_ovf(struct rcu_node *rnp, struct rcu_data *rdp) 
	if (ULONG_CMP_LT(rcu_seq_current(&rdp->gp_seq) + ULONG_MAX / 4,

			 rnp->gp_seq))

		WRITE_ONCE(rdp->gpwrap, true);

	if (ULONG_CMP_LT(rdp->rcu_iw_gpnum + ULONG_MAX / 4, rnp->gpnum))

		rdp->rcu_iw_gpnum = rnp->gpnum + ULONG_MAX / 4;

	if (ULONG_CMP_LT(rdp->rcu_iw_gp_seq + ULONG_MAX / 4, rnp->gp_seq))

		rdp->rcu_iw_gp_seq = rnp->gp_seq + ULONG_MAX / 4;

}



/*
@@ -1134,7 +1134,7 @@ static void rcu_iw_handler(struct irq_work *iwp) 
	rnp = rdp->mynode;

	raw_spin_lock_rcu_node(rnp);

	if (!WARN_ON_ONCE(!rdp->rcu_iw_pending)) {

		rdp->rcu_iw_gpnum = rnp->gpnum;

		rdp->rcu_iw_gp_seq = rnp->gp_seq;

		rdp->rcu_iw_pending = false;

	}

	raw_spin_unlock_rcu_node(rnp);
@@ -1231,11 +1231,11 @@ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) 
	if (jiffies - rdp->rsp->gp_start > rcu_jiffies_till_stall_check() / 2) {

		resched_cpu(rdp->cpu);

		if (IS_ENABLED(CONFIG_IRQ_WORK) &&

		    !rdp->rcu_iw_pending && rdp->rcu_iw_gpnum != rnp->gpnum &&

		    !rdp->rcu_iw_pending && rdp->rcu_iw_gp_seq != rnp->gp_seq &&

		    (rnp->ffmask & rdp->grpmask)) {

			init_irq_work(&rdp->rcu_iw, rcu_iw_handler);

			rdp->rcu_iw_pending = true;

			rdp->rcu_iw_gpnum = rnp->gpnum;

			rdp->rcu_iw_gp_seq = rnp->gp_seq;

			irq_work_queue_on(&rdp->rcu_iw, rdp->cpu);

		}

	}
@@ -3575,7 +3575,7 @@ rcu_init_percpu_data(int cpu, struct rcu_state *rsp) 
	rdp->rcu_qs_ctr_snap = per_cpu(rcu_dynticks.rcu_qs_ctr, cpu);

	rdp->core_needs_qs = false;

	rdp->rcu_iw_pending = false;

	rdp->rcu_iw_gpnum = rnp->gpnum - 1;

	rdp->rcu_iw_gp_seq = rnp->gp_seq - 1;

	trace_rcu_grace_period(rsp->name, rdp->gpnum, TPS("cpuonl"));

	raw_spin_unlock_irqrestore_rcu_node(rnp, flags);

}

kernel/rcu/tree.h

+1 −1
Original line number Diff line number Diff line
@@ -286,7 +286,7 @@ struct rcu_data { 
	/* ->rcu_iw* fields protected by leaf rcu_node ->lock. */

	struct irq_work rcu_iw;		/* Check for non-irq activity. */

	bool rcu_iw_pending;		/* Is ->rcu_iw pending? */

	unsigned long rcu_iw_gpnum;	/* ->gpnum associated with ->rcu_iw. */

	unsigned long rcu_iw_gp_seq;	/* ->gp_seq associated with ->rcu_iw. */



	int cpu;

	struct rcu_state *rsp;

kernel/rcu/tree_plugin.h

+1 −1
Original line number Diff line number Diff line
@@ -1763,7 +1763,7 @@ static void print_cpu_stall_info(struct rcu_state *rsp, int cpu) 
		ticks_value = rsp->gpnum - rdp->gpnum;

	}

	print_cpu_stall_fast_no_hz(fast_no_hz, cpu);

	delta = rdp->mynode->gpnum - rdp->rcu_iw_gpnum;

	delta = rcu_seq_ctr(rdp->mynode->gp_seq - rdp->rcu_iw_gp_seq);

	pr_err("\t%d-%c%c%c%c: (%lu %s) idle=%03x/%ld/%ld softirq=%u/%u fqs=%ld %s\n",

	       cpu,

	       "O."[!!cpu_online(cpu)],