2 * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition
3 * Internal non-public definitions that provide either classic
4 * or preemptible semantics.
6 * This program is free software; you can redistribute it and/or modify
7 * it under the terms of the GNU General Public License as published by
8 * the Free Software Foundation; either version 2 of the License, or
9 * (at your option) any later version.
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
16 * You should have received a copy of the GNU General Public License
17 * along with this program; if not, write to the Free Software
18 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
20 * Copyright (c) 2010 Linaro
22 * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
25 #include <linux/kthread.h>
26 #include <linux/module.h>
27 #include <linux/debugfs.h>
28 #include <linux/seq_file.h>
30 /* Global control variables for rcupdate callback mechanism. */
32 struct rcu_head *rcucblist; /* List of pending callbacks (CBs). */
33 struct rcu_head **donetail; /* ->next pointer of last "done" CB. */
34 struct rcu_head **curtail; /* ->next pointer of last CB. */
35 RCU_TRACE(long qlen); /* Number of pending CBs. */
36 RCU_TRACE(unsigned long gp_start); /* Start time for stalls. */
37 RCU_TRACE(unsigned long ticks_this_gp); /* Statistic for stalls. */
38 RCU_TRACE(unsigned long jiffies_stall); /* Jiffies at next stall. */
39 RCU_TRACE(char *name); /* Name of RCU type. */
42 /* Definition for rcupdate control block. */
43 static struct rcu_ctrlblk rcu_sched_ctrlblk = {
44 .donetail = &rcu_sched_ctrlblk.rcucblist,
45 .curtail = &rcu_sched_ctrlblk.rcucblist,
46 RCU_TRACE(.name = "rcu_sched")
49 static struct rcu_ctrlblk rcu_bh_ctrlblk = {
50 .donetail = &rcu_bh_ctrlblk.rcucblist,
51 .curtail = &rcu_bh_ctrlblk.rcucblist,
52 RCU_TRACE(.name = "rcu_bh")
55 #ifdef CONFIG_DEBUG_LOCK_ALLOC
56 int rcu_scheduler_active __read_mostly;
57 EXPORT_SYMBOL_GPL(rcu_scheduler_active);
58 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
60 #ifdef CONFIG_RCU_TRACE
62 static void check_cpu_stall(struct rcu_ctrlblk *rcp)
67 if (rcu_cpu_stall_suppress)
71 js = rcp->jiffies_stall;
72 if (*rcp->curtail && ULONG_CMP_GE(j, js)) {
73 pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n",
74 rcp->name, rcp->ticks_this_gp, rcu_dynticks_nesting,
75 jiffies - rcp->gp_start, rcp->qlen);
78 if (*rcp->curtail && ULONG_CMP_GE(j, js))
79 rcp->jiffies_stall = jiffies +
80 3 * rcu_jiffies_till_stall_check() + 3;
81 else if (ULONG_CMP_GE(j, js))
82 rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
85 static void check_cpu_stall_preempt(void);
87 #endif /* #ifdef CONFIG_RCU_TRACE */
89 static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp)
91 #ifdef CONFIG_RCU_TRACE
92 rcp->ticks_this_gp = 0;
93 rcp->gp_start = jiffies;
94 rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check();
95 #endif /* #ifdef CONFIG_RCU_TRACE */
98 static void check_cpu_stalls(void)
100 RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk));
101 RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk));
102 RCU_TRACE(check_cpu_stall_preempt());
106 * Because preemptible RCU does not exist, it never has any callbacks
109 static void rcu_preempt_remove_callbacks(struct rcu_ctrlblk *rcp)
114 * Because preemptible RCU does not exist, it never has any callbacks
117 static void rcu_preempt_process_callbacks(void)
121 /* Hold off callback invocation until early_initcall() time. */
122 static int rcu_scheduler_fully_active __read_mostly;
125 * Start up softirq processing of callbacks.
127 void invoke_rcu_callbacks(void)
129 if (rcu_scheduler_fully_active)
130 raise_softirq(RCU_SOFTIRQ);
133 #ifdef CONFIG_RCU_TRACE
136 * There is no callback kthread, so this thread is never it.
138 static bool rcu_is_callbacks_kthread(void)
143 #endif /* #ifdef CONFIG_RCU_TRACE */
145 static int __init rcu_scheduler_really_started(void)
147 rcu_scheduler_fully_active = 1;
148 open_softirq(RCU_SOFTIRQ, rcu_process_callbacks);
149 raise_softirq(RCU_SOFTIRQ); /* Invoke any callbacks from early boot. */
152 early_initcall(rcu_scheduler_really_started);
154 #ifdef CONFIG_DEBUG_LOCK_ALLOC
155 #include <linux/kernel_stat.h>
158 * During boot, we forgive RCU lockdep issues. After this function is
159 * invoked, we start taking RCU lockdep issues seriously.
161 void __init rcu_scheduler_starting(void)
163 WARN_ON(nr_context_switches() > 0);
164 rcu_scheduler_active = 1;
167 #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
169 #ifdef CONFIG_RCU_TRACE
171 static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n)
175 local_irq_save(flags);
177 local_irq_restore(flags);
181 * Dump statistics for TINY_RCU, such as they are.
183 static int show_tiny_stats(struct seq_file *m, void *unused)
185 seq_printf(m, "rcu_sched: qlen: %ld\n", rcu_sched_ctrlblk.qlen);
186 seq_printf(m, "rcu_bh: qlen: %ld\n", rcu_bh_ctrlblk.qlen);
190 static int show_tiny_stats_open(struct inode *inode, struct file *file)
192 return single_open(file, show_tiny_stats, NULL);
195 static const struct file_operations show_tiny_stats_fops = {
196 .owner = THIS_MODULE,
197 .open = show_tiny_stats_open,
200 .release = single_release,
203 static struct dentry *rcudir;
205 static int __init rcutiny_trace_init(void)
207 struct dentry *retval;
209 rcudir = debugfs_create_dir("rcu", NULL);
212 retval = debugfs_create_file("rcudata", 0444, rcudir,
213 NULL, &show_tiny_stats_fops);
218 debugfs_remove_recursive(rcudir);
222 static void __exit rcutiny_trace_cleanup(void)
224 debugfs_remove_recursive(rcudir);
227 module_init(rcutiny_trace_init);
228 module_exit(rcutiny_trace_cleanup);
230 MODULE_AUTHOR("Paul E. McKenney");
231 MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation");
232 MODULE_LICENSE("GPL");
234 static void check_cpu_stall_preempt(void)
238 #endif /* #ifdef CONFIG_RCU_TRACE */