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f41d911f8c
Create a kernel/rcutree_plugin.h file that contains definitions for preemptable RCU (or, under the #else branch of the #ifdef, empty definitions for the classic non-preemptable semantics). These definitions fit into plugins defined in kernel/rcutree.c for this purpose. This variant of preemptable RCU uses a new algorithm whose read-side expense is roughly that of classic hierarchical RCU under CONFIG_PREEMPT. This new algorithm's update-side expense is similar to that of classic hierarchical RCU, and, in absence of read-side preemption or blocking, is exactly that of classic hierarchical RCU. Perhaps more important, this new algorithm has a much simpler implementation, saving well over 1,000 lines of code compared to mainline's implementation of preemptable RCU, which will hopefully be retired in favor of this new algorithm. The simplifications are obtained by maintaining per-task nesting state for running tasks, and using a simple lock-protected algorithm to handle accounting when tasks block within RCU read-side critical sections, making use of lessons learned while creating numerous user-level RCU implementations over the past 18 months. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: laijs@cn.fujitsu.com Cc: dipankar@in.ibm.com Cc: akpm@linux-foundation.org Cc: mathieu.desnoyers@polymtl.ca Cc: josht@linux.vnet.ibm.com Cc: dvhltc@us.ibm.com Cc: niv@us.ibm.com Cc: peterz@infradead.org Cc: rostedt@goodmis.org LKML-Reference: <12509746134003-git-send-email-> Signed-off-by: Ingo Molnar <mingo@elte.hu>
338 lines
9.1 KiB
C
338 lines
9.1 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=%ld g=%ld pq=%d pqc=%ld 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 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,%ld,%ld,%d,%ld,%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 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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int level = 0;
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struct rcu_node *rnp;
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seq_printf(m, "c=%ld g=%ld s=%d jfq=%ld j=%x "
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"nfqs=%lu/nfqsng=%lu(%lu) fqlh=%lu\n",
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rsp->completed, rsp->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);
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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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seq_printf(m, "%lx/%lx %d:%d ^%d ",
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rnp->qsmask, rnp->qsmaskinit,
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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 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=%ld\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=%ld\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=%ld\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 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 cbr=%ld cng=%ld 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_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 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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