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![Paul E. McKenney](/assets/img/avatar_default.png)
The current implementation of expedited grace periods has the user task drive the grace period. This works, but has downsides: (1) The user task must awaken tasks piggybacking on this grace period, which can result in latencies rivaling that of the grace period itself, and (2) User tasks can receive signals, which interfere with RCU CPU stall warnings. This commit therefore uses workqueues to drive the grace periods, so that the user task need not do the awakening. A subsequent commit will remove the now-unnecessary code allowing for signals. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
495 lines
13 KiB
C
495 lines
13 KiB
C
/*
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* Read-Copy Update tracing for hierarchical 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, you can access it online at
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* http://www.gnu.org/licenses/gpl-2.0.html.
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*
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* Copyright IBM Corporation, 2008
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* Author: Paul E. McKenney
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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 <linux/atomic.h>
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#include <linux/bitops.h>
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#include <linux/completion.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 "tree.h"
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DECLARE_PER_CPU_SHARED_ALIGNED(unsigned long, rcu_qs_ctr);
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static int r_open(struct inode *inode, struct file *file,
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const struct seq_operations *op)
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{
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int ret = seq_open(file, op);
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if (!ret) {
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struct seq_file *m = (struct seq_file *)file->private_data;
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m->private = inode->i_private;
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}
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return ret;
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}
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static void *r_start(struct seq_file *m, loff_t *pos)
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{
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struct rcu_state *rsp = (struct rcu_state *)m->private;
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*pos = cpumask_next(*pos - 1, cpu_possible_mask);
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if ((*pos) < nr_cpu_ids)
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return per_cpu_ptr(rsp->rda, *pos);
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return NULL;
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}
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static void *r_next(struct seq_file *m, void *v, loff_t *pos)
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{
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(*pos)++;
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return r_start(m, pos);
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}
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static void r_stop(struct seq_file *m, void *v)
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{
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}
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static int show_rcubarrier(struct seq_file *m, void *v)
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{
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struct rcu_state *rsp = (struct rcu_state *)m->private;
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seq_printf(m, "bcc: %d bseq: %lu\n",
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atomic_read(&rsp->barrier_cpu_count),
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rsp->barrier_sequence);
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return 0;
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}
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static int rcubarrier_open(struct inode *inode, struct file *file)
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{
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return single_open(file, show_rcubarrier, inode->i_private);
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}
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static const struct file_operations rcubarrier_fops = {
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.owner = THIS_MODULE,
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.open = rcubarrier_open,
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.read = seq_read,
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.llseek = no_llseek,
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.release = single_release,
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};
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#ifdef CONFIG_RCU_BOOST
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static char convert_kthread_status(unsigned int kthread_status)
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{
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if (kthread_status > RCU_KTHREAD_MAX)
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return '?';
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return "SRWOY"[kthread_status];
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}
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#endif /* #ifdef CONFIG_RCU_BOOST */
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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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long ql, qll;
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if (!rdp->beenonline)
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return;
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seq_printf(m, "%3d%cc=%ld g=%ld cnq=%d/%d:%d",
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rdp->cpu,
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cpu_is_offline(rdp->cpu) ? '!' : ' ',
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ulong2long(rdp->completed), ulong2long(rdp->gpnum),
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rdp->cpu_no_qs.b.norm,
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rdp->rcu_qs_ctr_snap == per_cpu(rcu_qs_ctr, rdp->cpu),
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rdp->core_needs_qs);
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seq_printf(m, " dt=%d/%llx/%d df=%lu",
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atomic_read(&rdp->dynticks->dynticks),
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rdp->dynticks->dynticks_nesting,
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rdp->dynticks->dynticks_nmi_nesting,
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rdp->dynticks_fqs);
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seq_printf(m, " of=%lu", rdp->offline_fqs);
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rcu_nocb_q_lengths(rdp, &ql, &qll);
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qll += rdp->qlen_lazy;
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ql += rdp->qlen;
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seq_printf(m, " ql=%ld/%ld qs=%c%c%c%c",
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qll, ql,
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".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] !=
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rdp->nxttail[RCU_NEXT_TAIL]],
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".R"[rdp->nxttail[RCU_WAIT_TAIL] !=
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rdp->nxttail[RCU_NEXT_READY_TAIL]],
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".W"[rdp->nxttail[RCU_DONE_TAIL] !=
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rdp->nxttail[RCU_WAIT_TAIL]],
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".D"[&rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]]);
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#ifdef CONFIG_RCU_BOOST
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seq_printf(m, " kt=%d/%c ktl=%x",
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per_cpu(rcu_cpu_has_work, rdp->cpu),
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convert_kthread_status(per_cpu(rcu_cpu_kthread_status,
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rdp->cpu)),
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per_cpu(rcu_cpu_kthread_loops, rdp->cpu) & 0xffff);
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#endif /* #ifdef CONFIG_RCU_BOOST */
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seq_printf(m, " b=%ld", rdp->blimit);
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seq_printf(m, " ci=%lu nci=%lu co=%lu ca=%lu\n",
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rdp->n_cbs_invoked, rdp->n_nocbs_invoked,
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rdp->n_cbs_orphaned, rdp->n_cbs_adopted);
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}
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static int show_rcudata(struct seq_file *m, void *v)
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{
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print_one_rcu_data(m, (struct rcu_data *)v);
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return 0;
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}
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static const struct seq_operations rcudate_op = {
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.start = r_start,
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.next = r_next,
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.stop = r_stop,
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.show = show_rcudata,
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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 r_open(inode, file, &rcudate_op);
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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 = no_llseek,
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.release = seq_release,
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};
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static int show_rcuexp(struct seq_file *m, void *v)
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{
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int cpu;
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struct rcu_state *rsp = (struct rcu_state *)m->private;
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struct rcu_data *rdp;
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unsigned long s0 = 0, s1 = 0, s2 = 0, s3 = 0;
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for_each_possible_cpu(cpu) {
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rdp = per_cpu_ptr(rsp->rda, cpu);
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s0 += atomic_long_read(&rdp->exp_workdone0);
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s1 += atomic_long_read(&rdp->exp_workdone1);
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s2 += atomic_long_read(&rdp->exp_workdone2);
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s3 += atomic_long_read(&rdp->exp_workdone3);
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}
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seq_printf(m, "s=%lu wd0=%lu wd1=%lu wd2=%lu wd3=%lu n=%lu enq=%d sc=%lu\n",
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rsp->expedited_sequence, s0, s1, s2, s3,
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atomic_long_read(&rsp->expedited_normal),
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atomic_read(&rsp->expedited_need_qs),
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rsp->expedited_sequence / 2);
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return 0;
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}
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static int rcuexp_open(struct inode *inode, struct file *file)
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{
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return single_open(file, show_rcuexp, inode->i_private);
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}
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static const struct file_operations rcuexp_fops = {
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.owner = THIS_MODULE,
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.open = rcuexp_open,
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.read = seq_read,
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.llseek = no_llseek,
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.release = single_release,
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};
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#ifdef CONFIG_RCU_BOOST
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static void print_one_rcu_node_boost(struct seq_file *m, struct rcu_node *rnp)
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{
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seq_printf(m, "%d:%d tasks=%c%c%c%c kt=%c ntb=%lu neb=%lu nnb=%lu ",
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rnp->grplo, rnp->grphi,
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"T."[list_empty(&rnp->blkd_tasks)],
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"N."[!rnp->gp_tasks],
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"E."[!rnp->exp_tasks],
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"B."[!rnp->boost_tasks],
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convert_kthread_status(rnp->boost_kthread_status),
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rnp->n_tasks_boosted, rnp->n_exp_boosts,
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rnp->n_normal_boosts);
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seq_printf(m, "j=%04x bt=%04x\n",
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(int)(jiffies & 0xffff),
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(int)(rnp->boost_time & 0xffff));
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seq_printf(m, " balk: nt=%lu egt=%lu bt=%lu nb=%lu ny=%lu nos=%lu\n",
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rnp->n_balk_blkd_tasks,
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rnp->n_balk_exp_gp_tasks,
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rnp->n_balk_boost_tasks,
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rnp->n_balk_notblocked,
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rnp->n_balk_notyet,
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rnp->n_balk_nos);
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}
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static int show_rcu_node_boost(struct seq_file *m, void *unused)
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{
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struct rcu_node *rnp;
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rcu_for_each_leaf_node(&rcu_preempt_state, rnp)
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print_one_rcu_node_boost(m, rnp);
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return 0;
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}
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static int rcu_node_boost_open(struct inode *inode, struct file *file)
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{
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return single_open(file, show_rcu_node_boost, NULL);
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}
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static const struct file_operations rcu_node_boost_fops = {
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.owner = THIS_MODULE,
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.open = rcu_node_boost_open,
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.read = seq_read,
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.llseek = no_llseek,
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.release = single_release,
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};
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#endif /* #ifdef CONFIG_RCU_BOOST */
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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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struct rcu_node *rnp;
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gpnum = rsp->gpnum;
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seq_printf(m, "c=%ld g=%ld s=%d jfq=%ld j=%x ",
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ulong2long(rsp->completed), ulong2long(gpnum),
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rsp->gp_state,
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(long)(rsp->jiffies_force_qs - jiffies),
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(int)(jiffies & 0xffff));
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seq_printf(m, "nfqs=%lu/nfqsng=%lu(%lu) fqlh=%lu oqlen=%ld/%ld\n",
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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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READ_ONCE(rsp->n_force_qs_lh), rsp->qlen_lazy, rsp->qlen);
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for (rnp = &rsp->node[0]; rnp - &rsp->node[0] < rcu_num_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->%lx %c%c>%c %d:%d ^%d ",
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rnp->qsmask, rnp->qsmaskinit, rnp->qsmaskinitnext,
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".G"[rnp->gp_tasks != NULL],
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".E"[rnp->exp_tasks != NULL],
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".T"[!list_empty(&rnp->blkd_tasks)],
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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 *v)
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{
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struct rcu_state *rsp = (struct rcu_state *)m->private;
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print_one_rcu_state(m, rsp);
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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, inode->i_private);
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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 = no_llseek,
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.release = single_release,
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};
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static void show_one_rcugp(struct seq_file *m, struct rcu_state *rsp)
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{
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unsigned long flags;
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unsigned long completed;
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unsigned long gpnum;
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unsigned long gpage;
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unsigned long gpmax;
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struct rcu_node *rnp = &rsp->node[0];
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raw_spin_lock_irqsave_rcu_node(rnp, flags);
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completed = READ_ONCE(rsp->completed);
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gpnum = READ_ONCE(rsp->gpnum);
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if (completed == gpnum)
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gpage = 0;
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else
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gpage = jiffies - rsp->gp_start;
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gpmax = rsp->gp_max;
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raw_spin_unlock_irqrestore(&rnp->lock, flags);
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seq_printf(m, "completed=%ld gpnum=%ld age=%ld max=%ld\n",
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ulong2long(completed), ulong2long(gpnum), gpage, gpmax);
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}
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static int show_rcugp(struct seq_file *m, void *v)
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{
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struct rcu_state *rsp = (struct rcu_state *)m->private;
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show_one_rcugp(m, rsp);
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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, inode->i_private);
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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 = no_llseek,
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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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if (!rdp->beenonline)
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return;
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seq_printf(m, "%3d%cnp=%ld ",
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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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seq_printf(m, "qsp=%ld rpq=%ld cbr=%ld cng=%ld ",
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rdp->n_rp_core_needs_qs,
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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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seq_printf(m, "gpc=%ld gps=%ld nn=%ld ndw%ld\n",
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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_nocb_defer_wakeup,
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rdp->n_rp_need_nothing);
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}
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static int show_rcu_pending(struct seq_file *m, void *v)
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{
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print_one_rcu_pending(m, (struct rcu_data *)v);
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return 0;
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}
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static const struct seq_operations rcu_pending_op = {
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.start = r_start,
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.next = r_next,
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.stop = r_stop,
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.show = show_rcu_pending,
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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 r_open(inode, file, &rcu_pending_op);
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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 = no_llseek,
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.release = seq_release,
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};
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static int show_rcutorture(struct seq_file *m, void *unused)
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{
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seq_printf(m, "rcutorture test sequence: %lu %s\n",
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rcutorture_testseq >> 1,
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(rcutorture_testseq & 0x1) ? "(test in progress)" : "");
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seq_printf(m, "rcutorture update version number: %lu\n",
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rcutorture_vernum);
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return 0;
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}
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static int rcutorture_open(struct inode *inode, struct file *file)
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{
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return single_open(file, show_rcutorture, NULL);
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}
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static const struct file_operations rcutorture_fops = {
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.owner = THIS_MODULE,
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.open = rcutorture_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 rcutree_trace_init(void)
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{
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struct rcu_state *rsp;
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struct dentry *retval;
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struct dentry *rspdir;
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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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for_each_rcu_flavor(rsp) {
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rspdir = debugfs_create_dir(rsp->name, rcudir);
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if (!rspdir)
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goto free_out;
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retval = debugfs_create_file("rcudata", 0444,
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rspdir, rsp, &rcudata_fops);
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if (!retval)
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goto free_out;
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retval = debugfs_create_file("rcuexp", 0444,
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rspdir, rsp, &rcuexp_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,
|
|
rspdir, rsp, &rcu_pending_fops);
|
|
if (!retval)
|
|
goto free_out;
|
|
|
|
retval = debugfs_create_file("rcubarrier", 0444,
|
|
rspdir, rsp, &rcubarrier_fops);
|
|
if (!retval)
|
|
goto free_out;
|
|
|
|
#ifdef CONFIG_RCU_BOOST
|
|
if (rsp == &rcu_preempt_state) {
|
|
retval = debugfs_create_file("rcuboost", 0444,
|
|
rspdir, NULL, &rcu_node_boost_fops);
|
|
if (!retval)
|
|
goto free_out;
|
|
}
|
|
#endif
|
|
|
|
retval = debugfs_create_file("rcugp", 0444,
|
|
rspdir, rsp, &rcugp_fops);
|
|
if (!retval)
|
|
goto free_out;
|
|
|
|
retval = debugfs_create_file("rcuhier", 0444,
|
|
rspdir, rsp, &rcuhier_fops);
|
|
if (!retval)
|
|
goto free_out;
|
|
}
|
|
|
|
retval = debugfs_create_file("rcutorture", 0444, rcudir,
|
|
NULL, &rcutorture_fops);
|
|
if (!retval)
|
|
goto free_out;
|
|
return 0;
|
|
free_out:
|
|
debugfs_remove_recursive(rcudir);
|
|
return 1;
|
|
}
|
|
device_initcall(rcutree_trace_init);
|