renegade-project/linux-next
2
0
Fork 0
mirror of https://github.com/edk2-porting/linux-next.git synced 2024-12-26 22:24:09 +08:00
Code
0aa04b055e
linux-next/kernel/rcu/tree_trace.c
Paul E. McKenney 0aa04b055e rcu: Process offlining and onlining only at grace-period start 
Races between CPU hotplug and grace periods can be difficult to resolve,
so the ->onoff_mutex is used to exclude the two events.  Unfortunately,
this means that it is impossible for an outgoing CPU to perform the
last bits of its offlining from its last pass through the idle loop,
because sleeplocks cannot be acquired in that context.

This commit avoids these problems by buffering online and offline events
in a new ->qsmaskinitnext field in the leaf rcu_node structures.  When a
grace period starts, the events accumulated in this mask are applied to
the ->qsmaskinit field, and, if needed, up the rcu_node tree.  The special
case of all CPUs corresponding to a given leaf rcu_node structure being
offline while there are still elements in that structure's ->blkd_tasks
list is handled using a new ->wait_blkd_tasks field.  In this case,
propagating the offline bits up the tree is deferred until the beginning
of the grace period after all of the tasks have exited their RCU read-side
critical sections and removed themselves from the list, at which point
the ->wait_blkd_tasks flag is cleared.  If one of that leaf rcu_node
structure's CPUs comes back online before the list empties, then the
->wait_blkd_tasks flag is simply cleared.

This of course means that RCU's notion of which CPUs are offline can be
out of date.  This is OK because RCU need only wait on CPUs that were
online at the time that the grace period started.  In addition, RCU's
force-quiescent-state actions will handle the case where a CPU goes
offline after the grace period starts.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2015-03-12 15:19:37 -07:00

506 lines
13 KiB
C
Raw Blame History

/*
* Read-Copy Update tracing for classic implementation
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, you can access it online at
* http://www.gnu.org/licenses/gpl-2.0.html.
*
* Copyright IBM Corporation, 2008
*
* Papers: http://www.rdrop.com/users/paulmck/RCU
*
* For detailed explanation of Read-Copy Update mechanism see -
* Documentation/RCU
*
*/
#include <linux/types.h>
#include <linux/kernel.h>
#include <linux/init.h>
#include <linux/spinlock.h>
#include <linux/smp.h>
#include <linux/rcupdate.h>
#include <linux/interrupt.h>
#include <linux/sched.h>
#include <linux/atomic.h>
#include <linux/bitops.h>
#include <linux/module.h>
#include <linux/completion.h>
#include <linux/moduleparam.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/cpu.h>
#include <linux/mutex.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>
#define RCU_TREE_NONCORE
#include "tree.h"
DECLARE_PER_CPU_SHARED_ALIGNED(unsigned long, rcu_qs_ctr);
static int r_open(struct inode *inode, struct file *file,
const struct seq_operations *op)
{
int ret = seq_open(file, op);
if (!ret) {
struct seq_file *m = (struct seq_file *)file->private_data;
m->private = inode->i_private;
}
return ret;
}
static void *r_start(struct seq_file *m, loff_t *pos)
{
struct rcu_state *rsp = (struct rcu_state *)m->private;
*pos = cpumask_next(*pos - 1, cpu_possible_mask);
if ((*pos) < nr_cpu_ids)
return per_cpu_ptr(rsp->rda, *pos);
return NULL;
}
static void *r_next(struct seq_file *m, void *v, loff_t *pos)
{
(*pos)++;
return r_start(m, pos);
}
static void r_stop(struct seq_file *m, void *v)
{
}
static int show_rcubarrier(struct seq_file *m, void *v)
{
struct rcu_state *rsp = (struct rcu_state *)m->private;
seq_printf(m, "bcc: %d nbd: %lu\n",
atomic_read(&rsp->barrier_cpu_count),
rsp->n_barrier_done);
return 0;
}
static int rcubarrier_open(struct inode *inode, struct file *file)
{
return single_open(file, show_rcubarrier, inode->i_private);
}
static const struct file_operations rcubarrier_fops = {
.owner = THIS_MODULE,
.open = rcubarrier_open,
.read = seq_read,
.llseek = no_llseek,
.release = single_release,
};
#ifdef CONFIG_RCU_BOOST
static char convert_kthread_status(unsigned int kthread_status)
{
if (kthread_status > RCU_KTHREAD_MAX)
return '?';
return "SRWOY"[kthread_status];
}
#endif /* #ifdef CONFIG_RCU_BOOST */
static void print_one_rcu_data(struct seq_file *m, struct rcu_data *rdp)
{
long ql, qll;
if (!rdp->beenonline)
return;
seq_printf(m, "%3d%cc=%ld g=%ld pq=%d/%d qp=%d",
rdp->cpu,
cpu_is_offline(rdp->cpu) ? '!' : ' ',
ulong2long(rdp->completed), ulong2long(rdp->gpnum),
rdp->passed_quiesce,
rdp->rcu_qs_ctr_snap == per_cpu(rcu_qs_ctr, rdp->cpu),
rdp->qs_pending);
seq_printf(m, " dt=%d/%llx/%d df=%lu",
atomic_read(&rdp->dynticks->dynticks),
rdp->dynticks->dynticks_nesting,
rdp->dynticks->dynticks_nmi_nesting,
rdp->dynticks_fqs);
seq_printf(m, " of=%lu", rdp->offline_fqs);
rcu_nocb_q_lengths(rdp, &ql, &qll);
qll += rdp->qlen_lazy;
ql += rdp->qlen;
seq_printf(m, " ql=%ld/%ld qs=%c%c%c%c",
qll, ql,
".N"[rdp->nxttail[RCU_NEXT_READY_TAIL] !=
rdp->nxttail[RCU_NEXT_TAIL]],
".R"[rdp->nxttail[RCU_WAIT_TAIL] !=
rdp->nxttail[RCU_NEXT_READY_TAIL]],
".W"[rdp->nxttail[RCU_DONE_TAIL] !=
rdp->nxttail[RCU_WAIT_TAIL]],
".D"[&rdp->nxtlist != rdp->nxttail[RCU_DONE_TAIL]]);
#ifdef CONFIG_RCU_BOOST
seq_printf(m, " kt=%d/%c ktl=%x",
per_cpu(rcu_cpu_has_work, rdp->cpu),
convert_kthread_status(per_cpu(rcu_cpu_kthread_status,
rdp->cpu)),
per_cpu(rcu_cpu_kthread_loops, rdp->cpu) & 0xffff);
#endif /* #ifdef CONFIG_RCU_BOOST */
seq_printf(m, " b=%ld", rdp->blimit);
seq_printf(m, " ci=%lu nci=%lu co=%lu ca=%lu\n",
rdp->n_cbs_invoked, rdp->n_nocbs_invoked,
rdp->n_cbs_orphaned, rdp->n_cbs_adopted);
}
static int show_rcudata(struct seq_file *m, void *v)
{
print_one_rcu_data(m, (struct rcu_data *)v);
return 0;
}
static const struct seq_operations rcudate_op = {
.start = r_start,
.next = r_next,
.stop = r_stop,
.show = show_rcudata,
};
static int rcudata_open(struct inode *inode, struct file *file)
{
return r_open(inode, file, &rcudate_op);
}
static const struct file_operations rcudata_fops = {
.owner = THIS_MODULE,
.open = rcudata_open,
.read = seq_read,
.llseek = no_llseek,
.release = seq_release,
};
static int show_rcuexp(struct seq_file *m, void *v)
{
struct rcu_state *rsp = (struct rcu_state *)m->private;
seq_printf(m, "s=%lu d=%lu w=%lu tf=%lu wd1=%lu wd2=%lu n=%lu sc=%lu dt=%lu dl=%lu dx=%lu\n",
atomic_long_read(&rsp->expedited_start),
atomic_long_read(&rsp->expedited_done),
atomic_long_read(&rsp->expedited_wrap),
atomic_long_read(&rsp->expedited_tryfail),
atomic_long_read(&rsp->expedited_workdone1),
atomic_long_read(&rsp->expedited_workdone2),
atomic_long_read(&rsp->expedited_normal),
atomic_long_read(&rsp->expedited_stoppedcpus),
atomic_long_read(&rsp->expedited_done_tries),
atomic_long_read(&rsp->expedited_done_lost),
atomic_long_read(&rsp->expedited_done_exit));
return 0;
}
static int rcuexp_open(struct inode *inode, struct file *file)
{
return single_open(file, show_rcuexp, inode->i_private);
}
static const struct file_operations rcuexp_fops = {
.owner = THIS_MODULE,
.open = rcuexp_open,
.read = seq_read,
.llseek = no_llseek,
.release = single_release,
};
#ifdef CONFIG_RCU_BOOST
static void print_one_rcu_node_boost(struct seq_file *m, struct rcu_node *rnp)
{
seq_printf(m, "%d:%d tasks=%c%c%c%c kt=%c ntb=%lu neb=%lu nnb=%lu ",
rnp->grplo, rnp->grphi,
"T."[list_empty(&rnp->blkd_tasks)],
"N."[!rnp->gp_tasks],
"E."[!rnp->exp_tasks],
"B."[!rnp->boost_tasks],
convert_kthread_status(rnp->boost_kthread_status),
rnp->n_tasks_boosted, rnp->n_exp_boosts,
rnp->n_normal_boosts);
seq_printf(m, "j=%04x bt=%04x\n",
(int)(jiffies & 0xffff),
(int)(rnp->boost_time & 0xffff));
seq_printf(m, " balk: nt=%lu egt=%lu bt=%lu nb=%lu ny=%lu nos=%lu\n",
rnp->n_balk_blkd_tasks,
rnp->n_balk_exp_gp_tasks,
rnp->n_balk_boost_tasks,
rnp->n_balk_notblocked,
rnp->n_balk_notyet,
rnp->n_balk_nos);
}
static int show_rcu_node_boost(struct seq_file *m, void *unused)
{
struct rcu_node *rnp;
rcu_for_each_leaf_node(&rcu_preempt_state, rnp)
print_one_rcu_node_boost(m, rnp);
return 0;
}
static int rcu_node_boost_open(struct inode *inode, struct file *file)
{
return single_open(file, show_rcu_node_boost, NULL);
}
static const struct file_operations rcu_node_boost_fops = {
.owner = THIS_MODULE,
.open = rcu_node_boost_open,
.read = seq_read,
.llseek = no_llseek,
.release = single_release,
};
#endif /* #ifdef CONFIG_RCU_BOOST */
static void print_one_rcu_state(struct seq_file *m, struct rcu_state *rsp)
{
unsigned long gpnum;
int level = 0;
struct rcu_node *rnp;
gpnum = rsp->gpnum;
seq_printf(m, "c=%ld g=%ld s=%d jfq=%ld j=%x ",
ulong2long(rsp->completed), ulong2long(gpnum),
rsp->fqs_state,
(long)(rsp->jiffies_force_qs - jiffies),
(int)(jiffies & 0xffff));
seq_printf(m, "nfqs=%lu/nfqsng=%lu(%lu) fqlh=%lu oqlen=%ld/%ld\n",
rsp->n_force_qs, rsp->n_force_qs_ngp,
rsp->n_force_qs - rsp->n_force_qs_ngp,
ACCESS_ONCE(rsp->n_force_qs_lh), rsp->qlen_lazy, rsp->qlen);
for (rnp = &rsp->node[0]; rnp - &rsp->node[0] < rcu_num_nodes; rnp++) {
if (rnp->level != level) {
seq_puts(m, "\n");
level = rnp->level;
}
seq_printf(m, "%lx/%lx->%lx %c%c>%c %d:%d ^%d ",
rnp->qsmask, rnp->qsmaskinit, rnp->qsmaskinitnext,
".G"[rnp->gp_tasks != NULL],
".E"[rnp->exp_tasks != NULL],
".T"[!list_empty(&rnp->blkd_tasks)],
rnp->grplo, rnp->grphi, rnp->grpnum);
}
seq_puts(m, "\n");
}
static int show_rcuhier(struct seq_file *m, void *v)
{
struct rcu_state *rsp = (struct rcu_state *)m->private;
print_one_rcu_state(m, rsp);
return 0;
}
static int rcuhier_open(struct inode *inode, struct file *file)
{
return single_open(file, show_rcuhier, inode->i_private);
}
static const struct file_operations rcuhier_fops = {
.owner = THIS_MODULE,
.open = rcuhier_open,
.read = seq_read,
.llseek = no_llseek,
.release = single_release,
};
static void show_one_rcugp(struct seq_file *m, struct rcu_state *rsp)
{
unsigned long flags;
unsigned long completed;
unsigned long gpnum;
unsigned long gpage;
unsigned long gpmax;
struct rcu_node *rnp = &rsp->node[0];
raw_spin_lock_irqsave(&rnp->lock, flags);
completed = ACCESS_ONCE(rsp->completed);
gpnum = ACCESS_ONCE(rsp->gpnum);
if (completed == gpnum)
gpage = 0;
else
gpage = jiffies - rsp->gp_start;
gpmax = rsp->gp_max;
raw_spin_unlock_irqrestore(&rnp->lock, flags);
seq_printf(m, "completed=%ld gpnum=%ld age=%ld max=%ld\n",
ulong2long(completed), ulong2long(gpnum), gpage, gpmax);
}
static int show_rcugp(struct seq_file *m, void *v)
{
struct rcu_state *rsp = (struct rcu_state *)m->private;
show_one_rcugp(m, rsp);
return 0;
}
static int rcugp_open(struct inode *inode, struct file *file)
{
return single_open(file, show_rcugp, inode->i_private);
}
static const struct file_operations rcugp_fops = {
.owner = THIS_MODULE,
.open = rcugp_open,
.read = seq_read,
.llseek = no_llseek,
.release = single_release,
};
static void print_one_rcu_pending(struct seq_file *m, struct rcu_data *rdp)
{
if (!rdp->beenonline)
return;
seq_printf(m, "%3d%cnp=%ld ",
rdp->cpu,
cpu_is_offline(rdp->cpu) ? '!' : ' ',
rdp->n_rcu_pending);
seq_printf(m, "qsp=%ld rpq=%ld cbr=%ld cng=%ld ",
rdp->n_rp_qs_pending,
rdp->n_rp_report_qs,
rdp->n_rp_cb_ready,
rdp->n_rp_cpu_needs_gp);
seq_printf(m, "gpc=%ld gps=%ld nn=%ld ndw%ld\n",
rdp->n_rp_gp_completed,
rdp->n_rp_gp_started,
rdp->n_rp_nocb_defer_wakeup,
rdp->n_rp_need_nothing);
}
static int show_rcu_pending(struct seq_file *m, void *v)
{
print_one_rcu_pending(m, (struct rcu_data *)v);
return 0;
}
static const struct seq_operations rcu_pending_op = {
.start = r_start,
.next = r_next,
.stop = r_stop,
.show = show_rcu_pending,
};
static int rcu_pending_open(struct inode *inode, struct file *file)
{
return r_open(inode, file, &rcu_pending_op);
}
static const struct file_operations rcu_pending_fops = {
.owner = THIS_MODULE,
.open = rcu_pending_open,
.read = seq_read,
.llseek = no_llseek,
.release = seq_release,
};
static int show_rcutorture(struct seq_file *m, void *unused)
{
seq_printf(m, "rcutorture test sequence: %lu %s\n",
rcutorture_testseq >> 1,
(rcutorture_testseq & 0x1) ? "(test in progress)" : "");
seq_printf(m, "rcutorture update version number: %lu\n",
rcutorture_vernum);
return 0;
}
static int rcutorture_open(struct inode *inode, struct file *file)
{
return single_open(file, show_rcutorture, NULL);
}
static const struct file_operations rcutorture_fops = {
.owner = THIS_MODULE,
.open = rcutorture_open,
.read = seq_read,
.llseek = seq_lseek,
.release = single_release,
};
static struct dentry *rcudir;
static int __init rcutree_trace_init(void)
{
struct rcu_state *rsp;
struct dentry *retval;
struct dentry *rspdir;
rcudir = debugfs_create_dir("rcu", NULL);
if (!rcudir)
goto free_out;
for_each_rcu_flavor(rsp) {
rspdir = debugfs_create_dir(rsp->name, rcudir);
if (!rspdir)
goto free_out;
retval = debugfs_create_file("rcudata", 0444,
rspdir, rsp, &rcudata_fops);
if (!retval)
goto free_out;
retval = debugfs_create_file("rcuexp", 0444,
rspdir, rsp, &rcuexp_fops);
if (!retval)
goto free_out;
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;
}
static void __exit rcutree_trace_cleanup(void)
{
debugfs_remove_recursive(rcudir);
}
module_init(rcutree_trace_init);
module_exit(rcutree_trace_cleanup);
MODULE_AUTHOR("Paul E. McKenney");
MODULE_DESCRIPTION("Read-Copy Update tracing for hierarchical implementation");
MODULE_LICENSE("GPL");
View Git Blame Copy Permalink