Commit | Line | Data |
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bbad9379 | 1 | /* |
a57eb940 | 2 | * Read-Copy Update mechanism for mutual exclusion, the Bloatwatch edition |
bbad9379 | 3 | * Internal non-public definitions that provide either classic |
a57eb940 | 4 | * or preemptible semantics. |
bbad9379 PM |
5 | * |
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. | |
10 | * | |
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. | |
15 | * | |
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. | |
19 | * | |
a57eb940 | 20 | * Copyright (c) 2010 Linaro |
bbad9379 PM |
21 | * |
22 | * Author: Paul E. McKenney <paulmck@linux.vnet.ibm.com> | |
23 | */ | |
24 | ||
b2c0710c | 25 | #include <linux/kthread.h> |
bdfa97bf | 26 | #include <linux/module.h> |
9e571a82 PM |
27 | #include <linux/debugfs.h> |
28 | #include <linux/seq_file.h> | |
29 | ||
24278d14 PM |
30 | /* Global control variables for rcupdate callback mechanism. */ |
31 | struct rcu_ctrlblk { | |
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. */ | |
9e571a82 | 35 | RCU_TRACE(long qlen); /* Number of pending CBs. */ |
6bfc09e2 PM |
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. */ | |
e66c33d5 | 39 | RCU_TRACE(const char *name); /* Name of RCU type. */ |
24278d14 PM |
40 | }; |
41 | ||
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, | |
e99033c5 | 46 | RCU_TRACE(.name = "rcu_sched") |
24278d14 PM |
47 | }; |
48 | ||
49 | static struct rcu_ctrlblk rcu_bh_ctrlblk = { | |
50 | .donetail = &rcu_bh_ctrlblk.rcucblist, | |
51 | .curtail = &rcu_bh_ctrlblk.rcucblist, | |
e99033c5 | 52 | RCU_TRACE(.name = "rcu_bh") |
24278d14 PM |
53 | }; |
54 | ||
55 | #ifdef CONFIG_DEBUG_LOCK_ALLOC | |
318bdcd9 PM |
56 | #include <linux/kernel_stat.h> |
57 | ||
24278d14 PM |
58 | int rcu_scheduler_active __read_mostly; |
59 | EXPORT_SYMBOL_GPL(rcu_scheduler_active); | |
bbad9379 PM |
60 | |
61 | /* | |
62 | * During boot, we forgive RCU lockdep issues. After this function is | |
63 | * invoked, we start taking RCU lockdep issues seriously. | |
64 | */ | |
b2c0710c | 65 | void __init rcu_scheduler_starting(void) |
bbad9379 PM |
66 | { |
67 | WARN_ON(nr_context_switches() > 0); | |
68 | rcu_scheduler_active = 1; | |
69 | } | |
70 | ||
71 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
24278d14 | 72 | |
9e571a82 PM |
73 | #ifdef CONFIG_RCU_TRACE |
74 | ||
9e571a82 PM |
75 | static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n) |
76 | { | |
77 | unsigned long flags; | |
78 | ||
7a11e205 | 79 | local_irq_save(flags); |
9e571a82 | 80 | rcp->qlen -= n; |
7a11e205 | 81 | local_irq_restore(flags); |
9e571a82 PM |
82 | } |
83 | ||
84 | /* | |
85 | * Dump statistics for TINY_RCU, such as they are. | |
86 | */ | |
87 | static int show_tiny_stats(struct seq_file *m, void *unused) | |
88 | { | |
9e571a82 PM |
89 | seq_printf(m, "rcu_sched: qlen: %ld\n", rcu_sched_ctrlblk.qlen); |
90 | seq_printf(m, "rcu_bh: qlen: %ld\n", rcu_bh_ctrlblk.qlen); | |
91 | return 0; | |
92 | } | |
93 | ||
94 | static int show_tiny_stats_open(struct inode *inode, struct file *file) | |
95 | { | |
96 | return single_open(file, show_tiny_stats, NULL); | |
97 | } | |
98 | ||
99 | static const struct file_operations show_tiny_stats_fops = { | |
100 | .owner = THIS_MODULE, | |
101 | .open = show_tiny_stats_open, | |
102 | .read = seq_read, | |
103 | .llseek = seq_lseek, | |
104 | .release = single_release, | |
105 | }; | |
106 | ||
107 | static struct dentry *rcudir; | |
108 | ||
109 | static int __init rcutiny_trace_init(void) | |
110 | { | |
111 | struct dentry *retval; | |
112 | ||
113 | rcudir = debugfs_create_dir("rcu", NULL); | |
114 | if (!rcudir) | |
115 | goto free_out; | |
116 | retval = debugfs_create_file("rcudata", 0444, rcudir, | |
117 | NULL, &show_tiny_stats_fops); | |
118 | if (!retval) | |
119 | goto free_out; | |
120 | return 0; | |
121 | free_out: | |
122 | debugfs_remove_recursive(rcudir); | |
123 | return 1; | |
124 | } | |
125 | ||
126 | static void __exit rcutiny_trace_cleanup(void) | |
127 | { | |
128 | debugfs_remove_recursive(rcudir); | |
129 | } | |
130 | ||
131 | module_init(rcutiny_trace_init); | |
132 | module_exit(rcutiny_trace_cleanup); | |
133 | ||
134 | MODULE_AUTHOR("Paul E. McKenney"); | |
135 | MODULE_DESCRIPTION("Read-Copy Update tracing for tiny implementation"); | |
136 | MODULE_LICENSE("GPL"); | |
137 | ||
318bdcd9 PM |
138 | static void check_cpu_stall(struct rcu_ctrlblk *rcp) |
139 | { | |
140 | unsigned long j; | |
141 | unsigned long js; | |
142 | ||
143 | if (rcu_cpu_stall_suppress) | |
144 | return; | |
145 | rcp->ticks_this_gp++; | |
146 | j = jiffies; | |
147 | js = rcp->jiffies_stall; | |
148 | if (*rcp->curtail && ULONG_CMP_GE(j, js)) { | |
149 | pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n", | |
150 | rcp->name, rcp->ticks_this_gp, rcu_dynticks_nesting, | |
151 | jiffies - rcp->gp_start, rcp->qlen); | |
152 | dump_stack(); | |
153 | } | |
154 | if (*rcp->curtail && ULONG_CMP_GE(j, js)) | |
155 | rcp->jiffies_stall = jiffies + | |
156 | 3 * rcu_jiffies_till_stall_check() + 3; | |
157 | else if (ULONG_CMP_GE(j, js)) | |
158 | rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check(); | |
159 | } | |
160 | ||
318bdcd9 PM |
161 | static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp) |
162 | { | |
318bdcd9 PM |
163 | rcp->ticks_this_gp = 0; |
164 | rcp->gp_start = jiffies; | |
165 | rcp->jiffies_stall = jiffies + rcu_jiffies_till_stall_check(); | |
318bdcd9 PM |
166 | } |
167 | ||
168 | static void check_cpu_stalls(void) | |
169 | { | |
170 | RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk)); | |
171 | RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk)); | |
172 | } | |
14961444 PM |
173 | |
174 | #endif /* #ifdef CONFIG_RCU_TRACE */ |