Commit fc908ed3 authored by Paul E. McKenney's avatar Paul E. McKenney
Browse files

rcu: Make RCU_CPU_STALL_INFO include number of fqs attempts 



One way that an RCU CPU stall warning can happen is if the grace-period
kthread is not allowed to execute.  One proxy for this kthread's
forward progress is the number of force-quiescent-state (fqs) scans.
This commit therefore adds the number of fqs scans to the RCU CPU stall
warning printouts when CONFIG_RCU_CPU_STALL_INFO=y.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
parent e9408e4f

kernel/rcu/tree.c

+1 −0
Original line number Diff line number Diff line
@@ -1043,6 +1043,7 @@ static void record_gp_stall_check_time(struct rcu_state *rsp) 
	j1 = rcu_jiffies_till_stall_check();

	ACCESS_ONCE(rsp->jiffies_stall) = j + j1;

	rsp->jiffies_resched = j + j1 / 2;

	rsp->n_force_qs_gpstart = ACCESS_ONCE(rsp->n_force_qs);

}



/*

kernel/rcu/tree.h

+2 −0
Original line number Diff line number Diff line
@@ -492,6 +492,8 @@ struct rcu_state { 
						/*  for CPU stalls. */

	unsigned long jiffies_resched;		/* Time at which to resched */

						/*  a reluctant CPU. */

	unsigned long n_force_qs_gpstart;	/* Snapshot of n_force_qs at */

						/*  GP start. */

	unsigned long gp_max;			/* Maximum GP duration in */

						/*  jiffies. */

	const char *name;			/* Name of structure. */

kernel/rcu/tree_plugin.h

+2 −1
Original line number Diff line number Diff line
@@ -1898,11 +1898,12 @@ 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);

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

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

	       cpu, ticks_value, ticks_title,

	       atomic_read(&rdtp->dynticks) & 0xfff,

	       rdtp->dynticks_nesting, rdtp->dynticks_nmi_nesting,

	       rdp->softirq_snap, kstat_softirqs_cpu(RCU_SOFTIRQ, cpu),

	       ACCESS_ONCE(rsp->n_force_qs) - rsp->n_force_qs_gpstart,

	       fast_no_hz);

}

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