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 | |
87de1cfd PM |
17 | * along with this program; if not, you can access it online at |
18 | * http://www.gnu.org/licenses/gpl-2.0.html. | |
bbad9379 | 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> |
9fc9204e | 26 | #include <linux/init.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 | |
52d7e48b PM |
63 | * invoked, we start taking RCU lockdep issues seriously. Note that unlike |
64 | * Tree RCU, Tiny RCU transitions directly from RCU_SCHEDULER_INACTIVE | |
65 | * to RCU_SCHEDULER_RUNNING, skipping the RCU_SCHEDULER_INIT stage. | |
66 | * The reason for this is that Tiny RCU does not need kthreads, so does | |
67 | * not have to care about the fact that the scheduler is half-initialized | |
68 | * at a certain phase of the boot process. | |
bbad9379 | 69 | */ |
b2c0710c | 70 | void __init rcu_scheduler_starting(void) |
bbad9379 PM |
71 | { |
72 | WARN_ON(nr_context_switches() > 0); | |
52d7e48b | 73 | rcu_scheduler_active = RCU_SCHEDULER_RUNNING; |
bbad9379 PM |
74 | } |
75 | ||
76 | #endif /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */ | |
24278d14 | 77 | |
9e571a82 PM |
78 | #ifdef CONFIG_RCU_TRACE |
79 | ||
9e571a82 PM |
80 | static void rcu_trace_sub_qlen(struct rcu_ctrlblk *rcp, int n) |
81 | { | |
82 | unsigned long flags; | |
83 | ||
7a11e205 | 84 | local_irq_save(flags); |
9e571a82 | 85 | rcp->qlen -= n; |
7a11e205 | 86 | local_irq_restore(flags); |
9e571a82 PM |
87 | } |
88 | ||
89 | /* | |
90 | * Dump statistics for TINY_RCU, such as they are. | |
91 | */ | |
92 | static int show_tiny_stats(struct seq_file *m, void *unused) | |
93 | { | |
9e571a82 PM |
94 | seq_printf(m, "rcu_sched: qlen: %ld\n", rcu_sched_ctrlblk.qlen); |
95 | seq_printf(m, "rcu_bh: qlen: %ld\n", rcu_bh_ctrlblk.qlen); | |
96 | return 0; | |
97 | } | |
98 | ||
99 | static int show_tiny_stats_open(struct inode *inode, struct file *file) | |
100 | { | |
101 | return single_open(file, show_tiny_stats, NULL); | |
102 | } | |
103 | ||
104 | static const struct file_operations show_tiny_stats_fops = { | |
105 | .owner = THIS_MODULE, | |
106 | .open = show_tiny_stats_open, | |
107 | .read = seq_read, | |
108 | .llseek = seq_lseek, | |
109 | .release = single_release, | |
110 | }; | |
111 | ||
112 | static struct dentry *rcudir; | |
113 | ||
114 | static int __init rcutiny_trace_init(void) | |
115 | { | |
116 | struct dentry *retval; | |
117 | ||
118 | rcudir = debugfs_create_dir("rcu", NULL); | |
119 | if (!rcudir) | |
120 | goto free_out; | |
121 | retval = debugfs_create_file("rcudata", 0444, rcudir, | |
122 | NULL, &show_tiny_stats_fops); | |
123 | if (!retval) | |
124 | goto free_out; | |
125 | return 0; | |
126 | free_out: | |
127 | debugfs_remove_recursive(rcudir); | |
128 | return 1; | |
129 | } | |
9fc9204e | 130 | device_initcall(rcutiny_trace_init); |
9e571a82 | 131 | |
318bdcd9 PM |
132 | static void check_cpu_stall(struct rcu_ctrlblk *rcp) |
133 | { | |
134 | unsigned long j; | |
135 | unsigned long js; | |
136 | ||
137 | if (rcu_cpu_stall_suppress) | |
138 | return; | |
139 | rcp->ticks_this_gp++; | |
140 | j = jiffies; | |
7d0ae808 | 141 | js = READ_ONCE(rcp->jiffies_stall); |
ec1fe396 | 142 | if (rcp->rcucblist && ULONG_CMP_GE(j, js)) { |
318bdcd9 | 143 | pr_err("INFO: %s stall on CPU (%lu ticks this GP) idle=%llx (t=%lu jiffies q=%ld)\n", |
5f6130fa | 144 | rcp->name, rcp->ticks_this_gp, DYNTICK_TASK_EXIT_IDLE, |
318bdcd9 PM |
145 | jiffies - rcp->gp_start, rcp->qlen); |
146 | dump_stack(); | |
7d0ae808 PM |
147 | WRITE_ONCE(rcp->jiffies_stall, |
148 | jiffies + 3 * rcu_jiffies_till_stall_check() + 3); | |
ec1fe396 | 149 | } else if (ULONG_CMP_GE(j, js)) { |
7d0ae808 PM |
150 | WRITE_ONCE(rcp->jiffies_stall, |
151 | jiffies + rcu_jiffies_till_stall_check()); | |
ec1fe396 | 152 | } |
318bdcd9 PM |
153 | } |
154 | ||
318bdcd9 PM |
155 | static void reset_cpu_stall_ticks(struct rcu_ctrlblk *rcp) |
156 | { | |
318bdcd9 PM |
157 | rcp->ticks_this_gp = 0; |
158 | rcp->gp_start = jiffies; | |
7d0ae808 PM |
159 | WRITE_ONCE(rcp->jiffies_stall, |
160 | jiffies + rcu_jiffies_till_stall_check()); | |
318bdcd9 PM |
161 | } |
162 | ||
163 | static void check_cpu_stalls(void) | |
164 | { | |
165 | RCU_TRACE(check_cpu_stall(&rcu_bh_ctrlblk)); | |
166 | RCU_TRACE(check_cpu_stall(&rcu_sched_ctrlblk)); | |
167 | } | |
14961444 PM |
168 | |
169 | #endif /* #ifdef CONFIG_RCU_TRACE */ |