Root/kernel/trace/trace_workqueue.c

1/*
2 * Workqueue statistical tracer.
3 *
4 * Copyright (C) 2008 Frederic Weisbecker <fweisbec@gmail.com>
5 *
6 */
7
8
9#include <trace/events/workqueue.h>
10#include <linux/list.h>
11#include <linux/percpu.h>
12#include <linux/slab.h>
13#include <linux/kref.h>
14#include "trace_stat.h"
15#include "trace.h"
16
17
18/* A cpu workqueue thread */
19struct cpu_workqueue_stats {
20    struct list_head list;
21    struct kref kref;
22    int cpu;
23    pid_t pid;
24/* Can be inserted from interrupt or user context, need to be atomic */
25    atomic_t inserted;
26/*
27 * Don't need to be atomic, works are serialized in a single workqueue thread
28 * on a single CPU.
29 */
30    unsigned int executed;
31};
32
33/* List of workqueue threads on one cpu */
34struct workqueue_global_stats {
35    struct list_head list;
36    spinlock_t lock;
37};
38
39/* Don't need a global lock because allocated before the workqueues, and
40 * never freed.
41 */
42static DEFINE_PER_CPU(struct workqueue_global_stats, all_workqueue_stat);
43#define workqueue_cpu_stat(cpu) (&per_cpu(all_workqueue_stat, cpu))
44
45static void cpu_workqueue_stat_free(struct kref *kref)
46{
47    kfree(container_of(kref, struct cpu_workqueue_stats, kref));
48}
49
50/* Insertion of a work */
51static void
52probe_workqueue_insertion(void *ignore,
53              struct task_struct *wq_thread,
54              struct work_struct *work)
55{
56    int cpu = cpumask_first(&wq_thread->cpus_allowed);
57    struct cpu_workqueue_stats *node;
58    unsigned long flags;
59
60    spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
61    list_for_each_entry(node, &workqueue_cpu_stat(cpu)->list, list) {
62        if (node->pid == wq_thread->pid) {
63            atomic_inc(&node->inserted);
64            goto found;
65        }
66    }
67    pr_debug("trace_workqueue: entry not found\n");
68found:
69    spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
70}
71
72/* Execution of a work */
73static void
74probe_workqueue_execution(void *ignore,
75              struct task_struct *wq_thread,
76              struct work_struct *work)
77{
78    int cpu = cpumask_first(&wq_thread->cpus_allowed);
79    struct cpu_workqueue_stats *node;
80    unsigned long flags;
81
82    spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
83    list_for_each_entry(node, &workqueue_cpu_stat(cpu)->list, list) {
84        if (node->pid == wq_thread->pid) {
85            node->executed++;
86            goto found;
87        }
88    }
89    pr_debug("trace_workqueue: entry not found\n");
90found:
91    spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
92}
93
94/* Creation of a cpu workqueue thread */
95static void probe_workqueue_creation(void *ignore,
96                     struct task_struct *wq_thread, int cpu)
97{
98    struct cpu_workqueue_stats *cws;
99    unsigned long flags;
100
101    WARN_ON(cpu < 0);
102
103    /* Workqueues are sometimes created in atomic context */
104    cws = kzalloc(sizeof(struct cpu_workqueue_stats), GFP_ATOMIC);
105    if (!cws) {
106        pr_warning("trace_workqueue: not enough memory\n");
107        return;
108    }
109    INIT_LIST_HEAD(&cws->list);
110    kref_init(&cws->kref);
111    cws->cpu = cpu;
112    cws->pid = wq_thread->pid;
113
114    spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
115    list_add_tail(&cws->list, &workqueue_cpu_stat(cpu)->list);
116    spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
117}
118
119/* Destruction of a cpu workqueue thread */
120static void
121probe_workqueue_destruction(void *ignore, struct task_struct *wq_thread)
122{
123    /* Workqueue only execute on one cpu */
124    int cpu = cpumask_first(&wq_thread->cpus_allowed);
125    struct cpu_workqueue_stats *node, *next;
126    unsigned long flags;
127
128    spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
129    list_for_each_entry_safe(node, next, &workqueue_cpu_stat(cpu)->list,
130                            list) {
131        if (node->pid == wq_thread->pid) {
132            list_del(&node->list);
133            kref_put(&node->kref, cpu_workqueue_stat_free);
134            goto found;
135        }
136    }
137
138    pr_debug("trace_workqueue: don't find workqueue to destroy\n");
139found:
140    spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
141
142}
143
144static struct cpu_workqueue_stats *workqueue_stat_start_cpu(int cpu)
145{
146    unsigned long flags;
147    struct cpu_workqueue_stats *ret = NULL;
148
149
150    spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
151
152    if (!list_empty(&workqueue_cpu_stat(cpu)->list)) {
153        ret = list_entry(workqueue_cpu_stat(cpu)->list.next,
154                 struct cpu_workqueue_stats, list);
155        kref_get(&ret->kref);
156    }
157
158    spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
159
160    return ret;
161}
162
163static void *workqueue_stat_start(struct tracer_stat *trace)
164{
165    int cpu;
166    void *ret = NULL;
167
168    for_each_possible_cpu(cpu) {
169        ret = workqueue_stat_start_cpu(cpu);
170        if (ret)
171            return ret;
172    }
173    return NULL;
174}
175
176static void *workqueue_stat_next(void *prev, int idx)
177{
178    struct cpu_workqueue_stats *prev_cws = prev;
179    struct cpu_workqueue_stats *ret;
180    int cpu = prev_cws->cpu;
181    unsigned long flags;
182
183    spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
184    if (list_is_last(&prev_cws->list, &workqueue_cpu_stat(cpu)->list)) {
185        spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
186        do {
187            cpu = cpumask_next(cpu, cpu_possible_mask);
188            if (cpu >= nr_cpu_ids)
189                return NULL;
190        } while (!(ret = workqueue_stat_start_cpu(cpu)));
191        return ret;
192    } else {
193        ret = list_entry(prev_cws->list.next,
194                 struct cpu_workqueue_stats, list);
195        kref_get(&ret->kref);
196    }
197    spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
198
199    return ret;
200}
201
202static int workqueue_stat_show(struct seq_file *s, void *p)
203{
204    struct cpu_workqueue_stats *cws = p;
205    struct pid *pid;
206    struct task_struct *tsk;
207
208    pid = find_get_pid(cws->pid);
209    if (pid) {
210        tsk = get_pid_task(pid, PIDTYPE_PID);
211        if (tsk) {
212            seq_printf(s, "%3d %6d %6u %s\n", cws->cpu,
213                   atomic_read(&cws->inserted), cws->executed,
214                   tsk->comm);
215            put_task_struct(tsk);
216        }
217        put_pid(pid);
218    }
219
220    return 0;
221}
222
223static void workqueue_stat_release(void *stat)
224{
225    struct cpu_workqueue_stats *node = stat;
226
227    kref_put(&node->kref, cpu_workqueue_stat_free);
228}
229
230static int workqueue_stat_headers(struct seq_file *s)
231{
232    seq_printf(s, "# CPU INSERTED EXECUTED NAME\n");
233    seq_printf(s, "# | | | |\n");
234    return 0;
235}
236
237struct tracer_stat workqueue_stats __read_mostly = {
238    .name = "workqueues",
239    .stat_start = workqueue_stat_start,
240    .stat_next = workqueue_stat_next,
241    .stat_show = workqueue_stat_show,
242    .stat_release = workqueue_stat_release,
243    .stat_headers = workqueue_stat_headers
244};
245
246
247int __init stat_workqueue_init(void)
248{
249    if (register_stat_tracer(&workqueue_stats)) {
250        pr_warning("Unable to register workqueue stat tracer\n");
251        return 1;
252    }
253
254    return 0;
255}
256fs_initcall(stat_workqueue_init);
257
258/*
259 * Workqueues are created very early, just after pre-smp initcalls.
260 * So we must register our tracepoints at this stage.
261 */
262int __init trace_workqueue_early_init(void)
263{
264    int ret, cpu;
265
266    for_each_possible_cpu(cpu) {
267        spin_lock_init(&workqueue_cpu_stat(cpu)->lock);
268        INIT_LIST_HEAD(&workqueue_cpu_stat(cpu)->list);
269    }
270
271    ret = register_trace_workqueue_insertion(probe_workqueue_insertion, NULL);
272    if (ret)
273        goto out;
274
275    ret = register_trace_workqueue_execution(probe_workqueue_execution, NULL);
276    if (ret)
277        goto no_insertion;
278
279    ret = register_trace_workqueue_creation(probe_workqueue_creation, NULL);
280    if (ret)
281        goto no_execution;
282
283    ret = register_trace_workqueue_destruction(probe_workqueue_destruction, NULL);
284    if (ret)
285        goto no_creation;
286
287    return 0;
288
289no_creation:
290    unregister_trace_workqueue_creation(probe_workqueue_creation, NULL);
291no_execution:
292    unregister_trace_workqueue_execution(probe_workqueue_execution, NULL);
293no_insertion:
294    unregister_trace_workqueue_insertion(probe_workqueue_insertion, NULL);
295out:
296    pr_warning("trace_workqueue: unable to trace workqueues\n");
297
298    return 1;
299}
300early_initcall(trace_workqueue_early_init);
301

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