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![Paul E. McKenney](/assets/img/avatar_default.png)
Lai Jiangshan noted that up to 10% of the RCU_SOFTIRQ are spurious, and traced this down to the fact that the current grace-period machinery will uselessly raise RCU_SOFTIRQ when a given CPU needs to go through a quiescent state, but has not yet done so. In this situation, there might well be nothing that RCU_SOFTIRQ can do, and the overhead can be worth worrying about in the ksoftirqd case. This patch therefore avoids raising RCU_SOFTIRQ in this situation. Changes since v1 (http://lkml.org/lkml/2010/3/30/122 from Lai Jiangshan): o Omit the rcu_qs_pending() prechecks, as they aren't that much less expensive than the quiescent-state checks. o Merge with the set_need_resched() patch that reduces IPIs. o Add the new n_rp_report_qs field to the rcu_pending tracing output. o Update the tracing documentation accordingly. Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
347 lines
9.5 KiB
C
347 lines
9.5 KiB
C
/*
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* Read-Copy Update tracing for classic implementation
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright IBM Corporation, 2008
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*
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* Papers: http://www.rdrop.com/users/paulmck/RCU
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*
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* For detailed explanation of Read-Copy Update mechanism see -
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* Documentation/RCU
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*
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*/
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#include <linux/types.h>
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#include <linux/kernel.h>
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#include <linux/init.h>
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#include <linux/spinlock.h>
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#include <linux/smp.h>
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#include <linux/rcupdate.h>
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#include <linux/interrupt.h>
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#include <linux/sched.h>
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#include <asm/atomic.h>
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#include <linux/bitops.h>
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#include <linux/module.h>
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#include <linux/completion.h>
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#include <linux/moduleparam.h>
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#include <linux/percpu.h>
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#include <linux/notifier.h>
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#include <linux/cpu.h>
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#include <linux/mutex.h>
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#include <linux/debugfs.h>
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#include <linux/seq_file.h>
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#define RCU_TREE_NONCORE
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#include "rcutree.h"
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static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
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{
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if (!rdp->beenonline)
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return;
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seq_printf(m, "%3d%cc=%lu g=%lu pq=%d pqc=%lu qp=%d",
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rdp->cpu,
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cpu_is_offline(rdp->cpu) ? '!' : ' ',
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rdp->completed, rdp->gpnum,
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rdp->passed_quiesc, rdp->passed_quiesc_completed,
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rdp->qs_pending);
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#ifdef CONFIG_NO_HZ
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seq_printf(m, " dt=%d/%d dn=%d df=%lu",
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rdp->dynticks->dynticks,
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rdp->dynticks->dynticks_nesting,
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rdp->dynticks->dynticks_nmi,
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rdp->dynticks_fqs);
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#endif /* #ifdef CONFIG_NO_HZ */
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seq_printf(m, " of=%lu ri=%lu", rdp->offline_fqs, rdp->resched_ipi);
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seq_printf(m, " ql=%ld b=%ld\n", rdp->qlen, rdp->blimit);
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}
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#define PRINT_RCU_DATA(name, func, m) \
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do { \
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int _p_r_d_i; \
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\
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for_each_possible_cpu(_p_r_d_i) \
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func(m, &per_cpu(name, _p_r_d_i)); \
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} while (0)
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static int show_rcudata(struct seq_file *m, void *unused)
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{
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#ifdef CONFIG_TREE_PREEMPT_RCU
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seq_puts(m, "rcu_preempt:\n");
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PRINT_RCU_DATA(rcu_preempt_data, print_one_rcu_data, m);
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#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
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seq_puts(m, "rcu_sched:\n");
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PRINT_RCU_DATA(rcu_sched_data, print_one_rcu_data, m);
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seq_puts(m, "rcu_bh:\n");
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PRINT_RCU_DATA(rcu_bh_data, print_one_rcu_data, m);
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return 0;
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}
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static int rcudata_open(struct inode *inode, struct file *file)
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{
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return single_open(file, show_rcudata, NULL);
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}
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static const struct file_operations rcudata_fops = {
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.owner = THIS_MODULE,
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.open = rcudata_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = single_release,
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};
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static void print_one_rcu_data_csv(struct seq_file *m, struct rcu_data *rdp)
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{
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if (!rdp->beenonline)
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return;
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seq_printf(m, "%d,%s,%lu,%lu,%d,%lu,%d",
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rdp->cpu,
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cpu_is_offline(rdp->cpu) ? "\"N\"" : "\"Y\"",
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rdp->completed, rdp->gpnum,
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rdp->passed_quiesc, rdp->passed_quiesc_completed,
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rdp->qs_pending);
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#ifdef CONFIG_NO_HZ
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seq_printf(m, ",%d,%d,%d,%lu",
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rdp->dynticks->dynticks,
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rdp->dynticks->dynticks_nesting,
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rdp->dynticks->dynticks_nmi,
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rdp->dynticks_fqs);
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#endif /* #ifdef CONFIG_NO_HZ */
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seq_printf(m, ",%lu,%lu", rdp->offline_fqs, rdp->resched_ipi);
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seq_printf(m, ",%ld,%ld\n", rdp->qlen, rdp->blimit);
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}
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static int show_rcudata_csv(struct seq_file *m, void *unused)
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{
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seq_puts(m, "\"CPU\",\"Online?\",\"c\",\"g\",\"pq\",\"pqc\",\"pq\",");
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#ifdef CONFIG_NO_HZ
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seq_puts(m, "\"dt\",\"dt nesting\",\"dn\",\"df\",");
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#endif /* #ifdef CONFIG_NO_HZ */
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seq_puts(m, "\"of\",\"ri\",\"ql\",\"b\"\n");
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#ifdef CONFIG_TREE_PREEMPT_RCU
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seq_puts(m, "\"rcu_preempt:\"\n");
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PRINT_RCU_DATA(rcu_preempt_data, print_one_rcu_data_csv, m);
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#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
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seq_puts(m, "\"rcu_sched:\"\n");
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PRINT_RCU_DATA(rcu_sched_data, print_one_rcu_data_csv, m);
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seq_puts(m, "\"rcu_bh:\"\n");
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PRINT_RCU_DATA(rcu_bh_data, print_one_rcu_data_csv, m);
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return 0;
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}
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static int rcudata_csv_open(struct inode *inode, struct file *file)
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{
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return single_open(file, show_rcudata_csv, NULL);
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}
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static const struct file_operations rcudata_csv_fops = {
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.owner = THIS_MODULE,
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.open = rcudata_csv_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = single_release,
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};
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static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp)
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{
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unsigned long gpnum;
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int level = 0;
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int phase;
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struct rcu_node *rnp;
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gpnum = rsp->gpnum;
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seq_printf(m, "c=%lu g=%lu s=%d jfq=%ld j=%x "
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"nfqs=%lu/nfqsng=%lu(%lu) fqlh=%lu oqlen=%ld\n",
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rsp->completed, gpnum, rsp->signaled,
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(long)(rsp->jiffies_force_qs - jiffies),
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(int)(jiffies & 0xffff),
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rsp->n_force_qs, rsp->n_force_qs_ngp,
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rsp->n_force_qs - rsp->n_force_qs_ngp,
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rsp->n_force_qs_lh, rsp->orphan_qlen);
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for (rnp = &rsp->node[0]; rnp - &rsp->node[0] < NUM_RCU_NODES; rnp++) {
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if (rnp->level != level) {
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seq_puts(m, "\n");
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level = rnp->level;
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}
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phase = gpnum & 0x1;
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seq_printf(m, "%lx/%lx %c%c>%c%c %d:%d ^%d ",
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rnp->qsmask, rnp->qsmaskinit,
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"T."[list_empty(&rnp->blocked_tasks[phase])],
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"E."[list_empty(&rnp->blocked_tasks[phase + 2])],
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"T."[list_empty(&rnp->blocked_tasks[!phase])],
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"E."[list_empty(&rnp->blocked_tasks[!phase + 2])],
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rnp->grplo, rnp->grphi, rnp->grpnum);
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}
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seq_puts(m, "\n");
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}
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static int show_rcuhier(struct seq_file *m, void *unused)
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{
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#ifdef CONFIG_TREE_PREEMPT_RCU
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seq_puts(m, "rcu_preempt:\n");
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print_one_rcu_state(m, &rcu_preempt_state);
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#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
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seq_puts(m, "rcu_sched:\n");
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print_one_rcu_state(m, &rcu_sched_state);
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seq_puts(m, "rcu_bh:\n");
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print_one_rcu_state(m, &rcu_bh_state);
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return 0;
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}
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static int rcuhier_open(struct inode *inode, struct file *file)
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{
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return single_open(file, show_rcuhier, NULL);
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}
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static const struct file_operations rcuhier_fops = {
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.owner = THIS_MODULE,
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.open = rcuhier_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = single_release,
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};
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static int show_rcugp(struct seq_file *m, void *unused)
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{
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#ifdef CONFIG_TREE_PREEMPT_RCU
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seq_printf(m, "rcu_preempt: completed=%ld gpnum=%lu\n",
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rcu_preempt_state.completed, rcu_preempt_state.gpnum);
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#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
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seq_printf(m, "rcu_sched: completed=%ld gpnum=%lu\n",
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rcu_sched_state.completed, rcu_sched_state.gpnum);
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seq_printf(m, "rcu_bh: completed=%ld gpnum=%lu\n",
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rcu_bh_state.completed, rcu_bh_state.gpnum);
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return 0;
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}
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static int rcugp_open(struct inode *inode, struct file *file)
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{
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return single_open(file, show_rcugp, NULL);
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}
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static const struct file_operations rcugp_fops = {
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.owner = THIS_MODULE,
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.open = rcugp_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = single_release,
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};
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static void print_one_rcu_pending(struct seq_file *m, struct rcu_data *rdp)
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{
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seq_printf(m, "%3d%cnp=%ld "
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"qsp=%ld rpq=%ld cbr=%ld cng=%ld "
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"gpc=%ld gps=%ld nf=%ld nn=%ld\n",
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rdp->cpu,
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cpu_is_offline(rdp->cpu) ? '!' : ' ',
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rdp->n_rcu_pending,
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rdp->n_rp_qs_pending,
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rdp->n_rp_report_qs,
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rdp->n_rp_cb_ready,
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rdp->n_rp_cpu_needs_gp,
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rdp->n_rp_gp_completed,
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rdp->n_rp_gp_started,
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rdp->n_rp_need_fqs,
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rdp->n_rp_need_nothing);
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}
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static void print_rcu_pendings(struct seq_file *m, struct rcu_state *rsp)
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{
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int cpu;
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struct rcu_data *rdp;
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for_each_possible_cpu(cpu) {
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rdp = rsp->rda[cpu];
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if (rdp->beenonline)
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print_one_rcu_pending(m, rdp);
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}
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}
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static int show_rcu_pending(struct seq_file *m, void *unused)
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{
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#ifdef CONFIG_TREE_PREEMPT_RCU
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seq_puts(m, "rcu_preempt:\n");
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print_rcu_pendings(m, &rcu_preempt_state);
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#endif /* #ifdef CONFIG_TREE_PREEMPT_RCU */
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seq_puts(m, "rcu_sched:\n");
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print_rcu_pendings(m, &rcu_sched_state);
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seq_puts(m, "rcu_bh:\n");
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print_rcu_pendings(m, &rcu_bh_state);
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return 0;
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}
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static int rcu_pending_open(struct inode *inode, struct file *file)
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{
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return single_open(file, show_rcu_pending, NULL);
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}
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static const struct file_operations rcu_pending_fops = {
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.owner = THIS_MODULE,
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.open = rcu_pending_open,
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.read = seq_read,
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.llseek = seq_lseek,
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.release = single_release,
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};
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static struct dentry *rcudir;
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static int __init rcuclassic_trace_init(void)
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{
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struct dentry *retval;
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rcudir = debugfs_create_dir("rcu", NULL);
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if (!rcudir)
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goto free_out;
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retval = debugfs_create_file("rcudata", 0444, rcudir,
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NULL, &rcudata_fops);
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if (!retval)
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goto free_out;
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retval = debugfs_create_file("rcudata.csv", 0444, rcudir,
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NULL, &rcudata_csv_fops);
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if (!retval)
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goto free_out;
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retval = debugfs_create_file("rcugp", 0444, rcudir, NULL, &rcugp_fops);
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if (!retval)
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goto free_out;
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retval = debugfs_create_file("rcuhier", 0444, rcudir,
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NULL, &rcuhier_fops);
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if (!retval)
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goto free_out;
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retval = debugfs_create_file("rcu_pending", 0444, rcudir,
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NULL, &rcu_pending_fops);
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if (!retval)
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goto free_out;
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return 0;
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free_out:
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debugfs_remove_recursive(rcudir);
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return 1;
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}
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static void __exit rcuclassic_trace_cleanup(void)
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{
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debugfs_remove_recursive(rcudir);
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}
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module_init(rcuclassic_trace_init);
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module_exit(rcuclassic_trace_cleanup);
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MODULE_AUTHOR("Paul E. McKenney");
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MODULE_DESCRIPTION("Read-Copy Update tracing for hierarchical implementation");
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MODULE_LICENSE("GPL");
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