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(struct task_struct *wq_thread,
  53                           struct work_struct *work)
  54 {
  55         int cpu = cpumask_first(&wq_thread->cpus_allowed);
  56         struct cpu_workqueue_stats *node;
  57         unsigned long flags;
  58
  59         spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
  60         list_for_each_entry(node, &workqueue_cpu_stat(cpu)->list, list) {
  61                 if (node->pid == wq_thread->pid) {
  62                         atomic_inc(&node->inserted);
  63                         goto found;
  64                 }
  65         }
  66         pr_debug("trace_workqueue: entry not found\n");
  67 found:
  68         spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
  69 }
  70
  71 /* Execution of a work */
  72 static void
  73 probe_workqueue_execution(struct task_struct *wq_thread,
  74                           struct work_struct *work)
  75 {
  76         int cpu = cpumask_first(&wq_thread->cpus_allowed);
  77         struct cpu_workqueue_stats *node;
  78         unsigned long flags;
  79
  80         spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
  81         list_for_each_entry(node, &workqueue_cpu_stat(cpu)->list, list) {
  82                 if (node->pid == wq_thread->pid) {
  83                         node->executed++;
  84                         goto found;
  85                 }
  86         }
  87         pr_debug("trace_workqueue: entry not found\n");
  88 found:
  89         spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
  90 }
  91
  92 /* Creation of a cpu workqueue thread */
  93 static void probe_workqueue_creation(struct task_struct *wq_thread, int cpu)
  94 {
  95         struct cpu_workqueue_stats *cws;
  96         unsigned long flags;
  97
  98         WARN_ON(cpu < 0);
  99
 100         /* Workqueues are sometimes created in atomic context */
 101         cws = kzalloc(sizeof(struct cpu_workqueue_stats), GFP_ATOMIC);
 102         if (!cws) {
 103                 pr_warning("trace_workqueue: not enough memory\n");
 104                 return;
 105         }
 106         INIT_LIST_HEAD(&cws->list);
 107         kref_init(&cws->kref);
 108         cws->cpu = cpu;
 109         cws->pid = wq_thread->pid;
 110
 111         spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
 112         list_add_tail(&cws->list, &workqueue_cpu_stat(cpu)->list);
 113         spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
 114 }
 115
 116 /* Destruction of a cpu workqueue thread */
 117 static void probe_workqueue_destruction(struct task_struct *wq_thread)
 118 {
 119         /* Workqueue only execute on one cpu */
 120         int cpu = cpumask_first(&wq_thread->cpus_allowed);
 121         struct cpu_workqueue_stats *node, *next;
 122         unsigned long flags;
 123
 124         spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
 125         list_for_each_entry_safe(node, next, &workqueue_cpu_stat(cpu)->list,
 126                                                         list) {
 127                 if (node->pid == wq_thread->pid) {
 128                         list_del(&node->list);
 129                         kref_put(&node->kref, cpu_workqueue_stat_free);
 130                         goto found;
 131                 }
 132         }
 133
 134         pr_debug("trace_workqueue: don't find workqueue to destroy\n");
 135 found:
 136         spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
 137
 138 }
 139
 140 static struct cpu_workqueue_stats *workqueue_stat_start_cpu(int cpu)
 141 {
 142         unsigned long flags;
 143         struct cpu_workqueue_stats *ret = NULL;
 144
 145
 146         spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
 147
 148         if (!list_empty(&workqueue_cpu_stat(cpu)->list)) {
 149                 ret = list_entry(workqueue_cpu_stat(cpu)->list.next,
 150                                  struct cpu_workqueue_stats, list);
 151                 kref_get(&ret->kref);
 152         }
 153
 154         spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
 155
 156         return ret;
 157 }
 158
 159 static void *workqueue_stat_start(struct tracer_stat *trace)
 160 {
 161         int cpu;
 162         void *ret = NULL;
 163
 164         for_each_possible_cpu(cpu) {
 165                 ret = workqueue_stat_start_cpu(cpu);
 166                 if (ret)
 167                         return ret;
 168         }
 169         return NULL;
 170 }
 171
 172 static void *workqueue_stat_next(void *prev, int idx)
 173 {
 174         struct cpu_workqueue_stats *prev_cws = prev;
 175         struct cpu_workqueue_stats *ret;
 176         int cpu = prev_cws->cpu;
 177         unsigned long flags;
 178
 179         spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
 180         if (list_is_last(&prev_cws->list, &workqueue_cpu_stat(cpu)->list)) {
 181                 spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
 182                 do {
 183                         cpu = cpumask_next(cpu, cpu_possible_mask);
 184                         if (cpu >= nr_cpu_ids)
 185                                 return NULL;
 186                 } while (!(ret = workqueue_stat_start_cpu(cpu)));
 187                 return ret;
 188         } else {
 189                 ret = list_entry(prev_cws->list.next,
 190                                  struct cpu_workqueue_stats, list);
 191                 kref_get(&ret->kref);
 192         }
 193         spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
 194
 195         return ret;
 196 }
 197
 198 static int workqueue_stat_show(struct seq_file *s, void *p)
 199 {
 200         struct cpu_workqueue_stats *cws = p;
 201         struct pid *pid;
 202         struct task_struct *tsk;
 203
 204         pid = find_get_pid(cws->pid);
 205         if (pid) {
 206                 tsk = get_pid_task(pid, PIDTYPE_PID);
 207                 if (tsk) {
 208                         seq_printf(s, "%3d %6d     %6u       %s\n", cws->cpu,
 209                                    atomic_read(&cws->inserted), cws->executed,
 210                                    tsk->comm);
 211                         put_task_struct(tsk);
 212                 }
 213                 put_pid(pid);
 214         }
 215
 216         return 0;
 217 }
 218
 219 static void workqueue_stat_release(void *stat)
 220 {
 221         struct cpu_workqueue_stats *node = stat;
 222
 223         kref_put(&node->kref, cpu_workqueue_stat_free);
 224 }
 225
 226 static int workqueue_stat_headers(struct seq_file *s)
 227 {
 228         seq_printf(s, "# CPU  INSERTED  EXECUTED   NAME\n");
 229         seq_printf(s, "# |      |         |          |\n");
 230         return 0;
 231 }
 232
 233 struct tracer_stat workqueue_stats __read_mostly = {
 234         .name = "workqueues",
 235         .stat_start = workqueue_stat_start,
 236         .stat_next = workqueue_stat_next,
 237         .stat_show = workqueue_stat_show,
 238         .stat_release = workqueue_stat_release,
 239         .stat_headers = workqueue_stat_headers
 240 };
 241
 242
 243 int __init stat_workqueue_init(void)
 244 {
 245         if (register_stat_tracer(&workqueue_stats)) {
 246                 pr_warning("Unable to register workqueue stat tracer\n");
 247                 return 1;
 248         }
 249
 250         return 0;
 251 }
 252 fs_initcall(stat_workqueue_init);
 253
 254 /*
 255  * Workqueues are created very early, just after pre-smp initcalls.
 256  * So we must register our tracepoints at this stage.
 257  */
 258 int __init trace_workqueue_early_init(void)
 259 {
 260         int ret, cpu;
 261
 262         ret = register_trace_workqueue_insertion(probe_workqueue_insertion);
 263         if (ret)
 264                 goto out;
 265
 266         ret = register_trace_workqueue_execution(probe_workqueue_execution);
 267         if (ret)
 268                 goto no_insertion;
 269
 270         ret = register_trace_workqueue_creation(probe_workqueue_creation);
 271         if (ret)
 272                 goto no_execution;
 273
 274         ret = register_trace_workqueue_destruction(probe_workqueue_destruction);
 275         if (ret)
 276                 goto no_creation;
 277
 278         for_each_possible_cpu(cpu) {
 279                 spin_lock_init(&workqueue_cpu_stat(cpu)->lock);
 280                 INIT_LIST_HEAD(&workqueue_cpu_stat(cpu)->list);
 281         }
 282
 283         return 0;
 284
 285 no_creation:
 286         unregister_trace_workqueue_creation(probe_workqueue_creation);
 287 no_execution:
 288         unregister_trace_workqueue_execution(probe_workqueue_execution);
 289 no_insertion:
 290         unregister_trace_workqueue_insertion(probe_workqueue_insertion);
 291 out:
 292         pr_warning("trace_workqueue: unable to trace workqueues\n");
 293
 294         return 1;
 295 }
 296 early_initcall(trace_workqueue_early_init);