summaryrefslogtreecommitdiff
path: root/kernel/rcutiny_plugin.h
blob: bfe992407803505e9f1e69a492dd1947e3e50043 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
/*
 * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition
 * Internal non-public definitions that provide either classic
 * or preemptible semantics.
 *
 * 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, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
 *
 * Copyright (c) 2010 Linaro
 *
 * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
 */

#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/debugfs.h>
#include <linux/seq_file.h>

/* Global control variables for rcupdate callback mechanism. */
struct rcu_ctrlblk {
	struct rcu_head *rcucblist;	/* List of pending callbacks (CBs). */
	struct rcu_head **donetail;	/* ->next pointer of last "done" CB. */
	struct rcu_head **curtail;	/* ->next pointer of last CB. */
	RCU_TRACE(long qlen);		/* Number of pending CBs. */
	RCU_TRACE(unsigned long gp_start); /* Start time for stalls. */
	RCU_TRACE(unsigned long ticks_this_gp); /* Statistic for stalls. */
	RCU_TRACE(unsigned long jiffies_stall); /* Jiffies at next stall. */
	RCU_TRACE(char *name);		/* Name of RCU type. */
};

/* Definition for rcupdate control block. */
static struct rcu_ctrlblk rcu_sched_ctrlblk = {
	.donetail	= &rcu_sched_ctrlblk.rcucblist,
	.curtail	= &rcu_sched_ctrlblk.rcucblist,
	RCU_TRACE(.name = "rcu_sched")
};

static struct rcu_ctrlblk rcu_bh_ctrlblk = {
	.donetail	= &rcu_bh_ctrlblk.rcucblist,
	.curtail	= &rcu_bh_ctrlblk.rcucblist,
	RCU_TRACE(.name = "rcu_bh")
};

#ifdef CONFIG_DEBUG_LOCK_ALLOC
int rcu_scheduler_active __read_mostly;
EXPORT_SYMBOL_GPL(rcu_scheduler_active);
#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

#ifdef CONFIG_RCU_TRACE

static void check_cpu_stall(struct rcu_ctrlblk *rcp)
{
	unsigned long j;
	unsigned long js;

	if (rcu_cpu_stall_suppress)
		return;
	rcp->ticks_this_gp++;
	j = jiffies;
	js = rcp->jiffies_stall;
	if (*rcp->curtail && ULONG_CMP_GE(j, js)) {
		pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n",
		       rcp->name, rcp->ticks_this_gp, rcu_dynticks_nesting,
		       jiffies - rcp->gp_start, rcp->qlen);
		dump_stack();
	}
	if (*rcp->curtail && ULONG_CMP_GE(j, js))
		rcp->jiffies_stall = jiffies +
			3 * rcu_jiffies_till_stall_check() + 3;
	else if (ULONG_CMP_GE(j, js))
		rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
}

static void check_cpu_stall_preempt(void);

#endif /* #ifdef CONFIG_RCU_TRACE */

static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)
{
#ifdef CONFIG_RCU_TRACE
	rcp->ticks_this_gp = 0;
	rcp->gp_start = jiffies;
	rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
#endif /* #ifdef CONFIG_RCU_TRACE */
}

static void check_cpu_stalls(void)
{
	RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk));
	RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk));
	RCU_TRACE(check_cpu_stall_preempt());
}

/* Hold off callback invocation until early_initcall() time. */
static int rcu_scheduler_fully_active __read_mostly;

/*
 * Start up softirq processing of callbacks.
 */
void invoke_rcu_callbacks(void)
{
	if (rcu_scheduler_fully_active)
		raise_softirq(RCU_SOFTIRQ);
}

#ifdef CONFIG_RCU_TRACE

/*
 * There is no callback kthread, so this thread is never it.
 */
static bool rcu_is_callbacks_kthread(void)
{
	return false;
}

#endif /* #ifdef CONFIG_RCU_TRACE */

static int __init rcu_scheduler_really_started(void)
{
	rcu_scheduler_fully_active = 1;
	open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
	raise_softirq(RCU_SOFTIRQ);  /* Invoke any callbacks from early boot. */
	return 0;
}
early_initcall(rcu_scheduler_really_started);

#ifdef CONFIG_DEBUG_LOCK_ALLOC
#include <linux/kernel_stat.h>

/*
 * During boot, we forgive RCU lockdep issues.  After this function is
 * invoked, we start taking RCU lockdep issues seriously.
 */
void __init rcu_scheduler_starting(void)
{
	WARN_ON(nr_context_switches() > 0);
	rcu_scheduler_active = 1;
}

#endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */

#ifdef CONFIG_RCU_TRACE

static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n)
{
	unsigned long flags;

	local_irq_save(flags);
	rcp->qlen -= n;
	local_irq_restore(flags);
}

/*
 * Dump statistics for TINY_RCU, such as they are.
 */
static int show_tiny_stats(struct seq_file *m, void *unused)
{
	seq_printf(m, "rcu_sched: qlen: %ld\n", rcu_sched_ctrlblk.qlen);
	seq_printf(m, "rcu_bh: qlen: %ld\n", rcu_bh_ctrlblk.qlen);
	return 0;
}

static int show_tiny_stats_open(struct inode *inode, struct file *file)
{
	return single_open(file, show_tiny_stats, NULL);
}

static const struct file_operations show_tiny_stats_fops = {
	.owner = THIS_MODULE,
	.open = show_tiny_stats_open,
	.read = seq_read,
	.llseek = seq_lseek,
	.release = single_release,
};

static struct dentry *rcudir;

static int __init rcutiny_trace_init(void)
{
	struct dentry *retval;

	rcudir = debugfs_create_dir("rcu", NULL);
	if (!rcudir)
		goto free_out;
	retval = debugfs_create_file("rcudata", 0444, rcudir,
				     NULL, &show_tiny_stats_fops);
	if (!retval)
		goto free_out;
	return 0;
free_out:
	debugfs_remove_recursive(rcudir);
	return 1;
}

static void __exit rcutiny_trace_cleanup(void)
{
	debugfs_remove_recursive(rcudir);
}

module_init(rcutiny_trace_init);
module_exit(rcutiny_trace_cleanup);

MODULE_AUTHOR("Paul E. McKenney");
MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation");
MODULE_LICENSE("GPL");

static void check_cpu_stall_preempt(void)
{
}

#endif /* #ifdef CONFIG_RCU_TRACE */