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 */
  19 struct 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 */
  34 struct 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  */
  42 static DEFINE_PER_CPU(struct workqueue_global_stats, all_workqueue_stat);
  43 #define workqueue_cpu_stat(cpu) (&per_cpu(all_workqueue_stat, cpu))
  44
  45 static 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 */
  51 static void
  52 probe_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");
  68 found:
  69         spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
  70 }
  71
  72 /* Execution of a work */
  73 static void
  74 probe_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");
  90 found:
  91         spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
  92 }
  93
  94 /* Creation of a cpu workqueue thread */
  95 static 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 */
 120 static void
 121 probe_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");
 139 found:
 140         spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
 141
 142 }
 143
 144 static 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
 163 static 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
 176 static 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
 202 static 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
 223 static 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
 230 static 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
 237 struct 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
 247 int __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 }
 256 fs_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  */
 262 int __init trace_workqueue_early_init(void)
 263 {
 264         int ret, cpu;
 265
 266         ret = register_trace_workqueue_insertion(probe_workqueue_insertion, NULL);
 267         if (ret)
 268                 goto out;
 269
 270         ret = register_trace_workqueue_execution(probe_workqueue_execution, NULL);
 271         if (ret)
 272                 goto no_insertion;
 273
 274         ret = register_trace_workqueue_creation(probe_workqueue_creation, NULL);
 275         if (ret)
 276                 goto no_execution;
 277
 278         ret = register_trace_workqueue_destruction(probe_workqueue_destruction, NULL);
 279         if (ret)
 280                 goto no_creation;
 281
 282         for_each_possible_cpu(cpu) {
 283                 spin_lock_init(&workqueue_cpu_stat(cpu)->lock);
 284                 INIT_LIST_HEAD(&workqueue_cpu_stat(cpu)->list);
 285         }
 286
 287         return 0;
 288
 289 no_creation:
 290         unregister_trace_workqueue_creation(probe_workqueue_creation, NULL);
 291 no_execution:
 292         unregister_trace_workqueue_execution(probe_workqueue_execution, NULL);
 293 no_insertion:
 294         unregister_trace_workqueue_insertion(probe_workqueue_insertion, NULL);
 295 out:
 296         pr_warning("trace_workqueue: unable to trace workqueues\n");
 297
 298         return 1;
 299 }
 300 early_initcall(trace_workqueue_early_init);