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