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Commit 59b73a27 authored by Paul E. McKenney's avatar Paul E. McKenney
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rcu: Move FAST_NO_HZ stall-warning code to tree_stall.h 



This commit further consolidates the stall-warning code by moving
print_cpu_stall_info() and its helper functions along with
zero_cpu_stall_ticks() to kernel/rcu/tree_stall.h.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.ibm.com>
parent 40e69ac7

kernel/rcu/tree.h

+0 −1
Original line number Diff line number Diff line
@@ -416,7 +416,6 @@ static void rcu_prepare_for_idle(void); 
static bool rcu_preempt_has_tasks(struct rcu_node *rnp);

static bool rcu_preempt_need_deferred_qs(struct task_struct *t);

static void rcu_preempt_deferred_qs(struct task_struct *t);

static void print_cpu_stall_info(int cpu);

static void zero_cpu_stall_ticks(struct rcu_data *rdp);

static bool rcu_nocb_cpu_needs_barrier(int cpu);

static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp);

kernel/rcu/tree_plugin.h

+0 −80
Original line number Diff line number Diff line
@@ -1528,86 +1528,6 @@ static void rcu_cleanup_after_idle(void) 


#endif /* #else #if !defined(CONFIG_RCU_FAST_NO_HZ) */



#ifdef CONFIG_RCU_FAST_NO_HZ



static void print_cpu_stall_fast_no_hz(char *cp, int cpu)

{

	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);



	sprintf(cp, "last_accelerate: %04lx/%04lx, Nonlazy posted: %c%c%c",

		rdp->last_accelerate & 0xffff, jiffies & 0xffff,

		".l"[rdp->all_lazy],

		".L"[!rcu_segcblist_n_nonlazy_cbs(&rdp->cblist)],

		".D"[!rdp->tick_nohz_enabled_snap]);

}



#else /* #ifdef CONFIG_RCU_FAST_NO_HZ */



static void print_cpu_stall_fast_no_hz(char *cp, int cpu)

{

	*cp = '\0';

}



#endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */



/*

 * Print out diagnostic information for the specified stalled CPU.

 *

 * If the specified CPU is aware of the current RCU grace period, then

 * print the number of scheduling clock interrupts the CPU has taken

 * during the time that it has been aware.  Otherwise, print the number

 * of RCU grace periods that this CPU is ignorant of, for example, "1"

 * if the CPU was aware of the previous grace period.

 *

 * Also print out idle and (if CONFIG_RCU_FAST_NO_HZ) idle-entry info.

 */

static void print_cpu_stall_info(int cpu)

{

	unsigned long delta;

	char fast_no_hz[72];

	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);

	char *ticks_title;

	unsigned long ticks_value;



	/*

	 * We could be printing a lot while holding a spinlock.  Avoid

	 * triggering hard lockup.

	 */

	touch_nmi_watchdog();



	ticks_value = rcu_seq_ctr(rcu_state.gp_seq - rdp->gp_seq);

	if (ticks_value) {

		ticks_title = "GPs behind";

	} else {

		ticks_title = "ticks this GP";

		ticks_value = rdp->ticks_this_gp;

	}

	print_cpu_stall_fast_no_hz(fast_no_hz, cpu);

	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/%#lx softirq=%u/%u fqs=%ld %s\n",

	       cpu,

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

	       "o."[!!(rdp->grpmask & rdp->mynode->qsmaskinit)],

	       "N."[!!(rdp->grpmask & rdp->mynode->qsmaskinitnext)],

	       !IS_ENABLED(CONFIG_IRQ_WORK) ? '?' :

			rdp->rcu_iw_pending ? (int)min(delta, 9UL) + '0' :

				"!."[!delta],

	       ticks_value, ticks_title,

	       rcu_dynticks_snap(rdp) & 0xfff,

	       rdp->dynticks_nesting, rdp->dynticks_nmi_nesting,

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

	       READ_ONCE(rcu_state.n_force_qs) - rcu_state.n_force_qs_gpstart,

	       fast_no_hz);

}



/* Zero ->ticks_this_gp and snapshot the number of RCU softirq handlers. */

static void zero_cpu_stall_ticks(struct rcu_data *rdp)

{

	rdp->ticks_this_gp = 0;

	rdp->softirq_snap = kstat_softirqs_cpu(RCU_SOFTIRQ, smp_processor_id());

	WRITE_ONCE(rdp->last_fqs_resched, jiffies);

}



#ifdef CONFIG_RCU_NOCB_CPU



/*

kernel/rcu/tree_stall.h

+80 −0
Original line number Diff line number Diff line
@@ -223,6 +223,86 @@ static void panic_on_rcu_stall(void) 
		panic("RCU Stall\n");

}



#ifdef CONFIG_RCU_FAST_NO_HZ



static void print_cpu_stall_fast_no_hz(char *cp, int cpu)

{

	struct rcu_data *rdp = &per_cpu(rcu_data, cpu);



	sprintf(cp, "last_accelerate: %04lx/%04lx, Nonlazy posted: %c%c%c",

		rdp->last_accelerate & 0xffff, jiffies & 0xffff,

		".l"[rdp->all_lazy],

		".L"[!rcu_segcblist_n_nonlazy_cbs(&rdp->cblist)],

		".D"[!rdp->tick_nohz_enabled_snap]);

}



#else /* #ifdef CONFIG_RCU_FAST_NO_HZ */



static void print_cpu_stall_fast_no_hz(char *cp, int cpu)

{

	*cp = '\0';

}



#endif /* #else #ifdef CONFIG_RCU_FAST_NO_HZ */



/*

 * Print out diagnostic information for the specified stalled CPU.

 *

 * If the specified CPU is aware of the current RCU grace period, then

 * print the number of scheduling clock interrupts the CPU has taken

 * during the time that it has been aware.  Otherwise, print the number

 * of RCU grace periods that this CPU is ignorant of, for example, "1"

 * if the CPU was aware of the previous grace period.

 *

 * Also print out idle and (if CONFIG_RCU_FAST_NO_HZ) idle-entry info.

 */

static void print_cpu_stall_info(int cpu)

{

	unsigned long delta;

	char fast_no_hz[72];

	struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu);

	char *ticks_title;

	unsigned long ticks_value;



	/*

	 * We could be printing a lot while holding a spinlock.  Avoid

	 * triggering hard lockup.

	 */

	touch_nmi_watchdog();



	ticks_value = rcu_seq_ctr(rcu_state.gp_seq - rdp->gp_seq);

	if (ticks_value) {

		ticks_title = "GPs behind";

	} else {

		ticks_title = "ticks this GP";

		ticks_value = rdp->ticks_this_gp;

	}

	print_cpu_stall_fast_no_hz(fast_no_hz, cpu);

	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/%#lx softirq=%u/%u fqs=%ld %s\n",

	       cpu,

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

	       "o."[!!(rdp->grpmask & rdp->mynode->qsmaskinit)],

	       "N."[!!(rdp->grpmask & rdp->mynode->qsmaskinitnext)],

	       !IS_ENABLED(CONFIG_IRQ_WORK) ? '?' :

			rdp->rcu_iw_pending ? (int)min(delta, 9UL) + '0' :

				"!."[!delta],

	       ticks_value, ticks_title,

	       rcu_dynticks_snap(rdp) & 0xfff,

	       rdp->dynticks_nesting, rdp->dynticks_nmi_nesting,

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

	       READ_ONCE(rcu_state.n_force_qs) - rcu_state.n_force_qs_gpstart,

	       fast_no_hz);

}



/* Zero ->ticks_this_gp and snapshot the number of RCU softirq handlers. */

static void zero_cpu_stall_ticks(struct rcu_data *rdp)

{

	rdp->ticks_this_gp = 0;

	rdp->softirq_snap = kstat_softirqs_cpu(RCU_SOFTIRQ, smp_processor_id());

	WRITE_ONCE(rdp->last_fqs_resched, jiffies);

}



static void print_other_cpu_stall(unsigned long gp_seq)

{

	int cpu;