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/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, *next;
  51         unsigned long flags;
  52
  53         spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
  54         list_for_each_entry_safe(node, next, &workqueue_cpu_stat(cpu)->list,
  55                                                         list) {
  56                 if (node->pid == wq_thread->pid) {
  57                         atomic_inc(&node->inserted);
  58                         goto found;
  59                 }
  60         }
  61         pr_debug("trace_workqueue: entry not found\n");
  62 found:
  63         spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
  64 }
  65
  66 /* Execution of a work */
  67 static void
  68 probe_workqueue_execution(struct task_struct *wq_thread,
  69                           struct work_struct *work)
  70 {
  71         int cpu = cpumask_first(&wq_thread->cpus_allowed);
  72         struct cpu_workqueue_stats *node, *next;
  73         unsigned long flags;
  74
  75         spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
  76         list_for_each_entry_safe(node, next, &workqueue_cpu_stat(cpu)->list,
  77                                                         list) {
  78                 if (node->pid == wq_thread->pid) {
  79                         node->executed++;
  80                         goto found;
  81                 }
  82         }
  83         pr_debug("trace_workqueue: entry not found\n");
  84 found:
  85         spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
  86 }
  87
  88 /* Creation of a cpu workqueue thread */
  89 static void probe_workqueue_creation(struct task_struct *wq_thread, int cpu)
  90 {
  91         struct cpu_workqueue_stats *cws;
  92         unsigned long flags;
  93
  94         WARN_ON(cpu < 0);
  95
  96         /* Workqueues are sometimes created in atomic context */
  97         cws = kzalloc(sizeof(struct cpu_workqueue_stats), GFP_ATOMIC);
  98         if (!cws) {
  99                 pr_warning("trace_workqueue: not enough memory\n");
 100                 return;
 101         }
 102         INIT_LIST_HEAD(&cws->list);
 103         cws->cpu = cpu;
 104
 105         cws->pid = wq_thread->pid;
 106
 107         spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
 108         if (list_empty(&workqueue_cpu_stat(cpu)->list))
 109                 cws->first_entry = true;
 110         list_add_tail(&cws->list, &workqueue_cpu_stat(cpu)->list);
 111         spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
 112 }
 113
 114 /* Destruction of a cpu workqueue thread */
 115 static void probe_workqueue_destruction(struct task_struct *wq_thread)
 116 {
 117         /* Workqueue only execute on one cpu */
 118         int cpu = cpumask_first(&wq_thread->cpus_allowed);
 119         struct cpu_workqueue_stats *node, *next;
 120         unsigned long flags;
 121
 122         spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
 123         list_for_each_entry_safe(node, next, &workqueue_cpu_stat(cpu)->list,
 124                                                         list) {
 125                 if (node->pid == wq_thread->pid) {
 126                         list_del(&node->list);
 127                         kfree(node);
 128                         goto found;
 129                 }
 130         }
 131
 132         pr_debug("trace_workqueue: don't find workqueue to destroy\n");
 133 found:
 134         spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
 135
 136 }
 137
 138 static struct cpu_workqueue_stats *workqueue_stat_start_cpu(int cpu)
 139 {
 140         unsigned long flags;
 141         struct cpu_workqueue_stats *ret = NULL;
 142
 143
 144         spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
 145
 146         if (!list_empty(&workqueue_cpu_stat(cpu)->list))
 147                 ret = list_entry(workqueue_cpu_stat(cpu)->list.next,
 148                                  struct cpu_workqueue_stats, list);
 149
 150         spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
 151
 152         return ret;
 153 }
 154
 155 static void *workqueue_stat_start(void)
 156 {
 157         int cpu;
 158         void *ret = NULL;
 159
 160         for_each_possible_cpu(cpu) {
 161                 ret = workqueue_stat_start_cpu(cpu);
 162                 if (ret)
 163                         return ret;
 164         }
 165         return NULL;
 166 }
 167
 168 static void *workqueue_stat_next(void *prev, int idx)
 169 {
 170         struct cpu_workqueue_stats *prev_cws = prev;
 171         int cpu = prev_cws->cpu;
 172         unsigned long flags;
 173         void *ret = NULL;
 174
 175         spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
 176         if (list_is_last(&prev_cws->list, &workqueue_cpu_stat(cpu)->list)) {
 177                 spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
 178                 do {
 179                         cpu = cpumask_next(cpu, cpu_possible_mask);
 180                         if (cpu >= nr_cpu_ids)
 181                                 return NULL;
 182                 } while (!(ret = workqueue_stat_start_cpu(cpu)));
 183                 return ret;
 184         }
 185         spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
 186
 187         return list_entry(prev_cws->list.next, struct cpu_workqueue_stats,
 188                           list);
 189 }
 190
 191 static int workqueue_stat_show(struct seq_file *s, void *p)
 192 {
 193         struct cpu_workqueue_stats *cws = p;
 194         unsigned long flags;
 195         int cpu = cws->cpu;
 196         struct task_struct *tsk = find_task_by_vpid(cws->pid);
 197
 198         seq_printf(s, "%3d %6d     %6u       %s\n", cws->cpu,
 199                    atomic_read(&cws->inserted),
 200                    cws->executed,
 201                    tsk ? tsk->comm : "<...>");
 202
 203         spin_lock_irqsave(&workqueue_cpu_stat(cpu)->lock, flags);
 204         if (&cws->list == workqueue_cpu_stat(cpu)->list.next)
 205                 seq_printf(s, "\n");
 206         spin_unlock_irqrestore(&workqueue_cpu_stat(cpu)->lock, flags);
 207
 208         return 0;
 209 }
 210
 211 static int workqueue_stat_headers(struct seq_file *s)
 212 {
 213         seq_printf(s, "# CPU  INSERTED  EXECUTED   NAME\n");
 214         seq_printf(s, "# |      |         |          |\n\n");
 215         return 0;
 216 }
 217
 218 struct tracer_stat workqueue_stats __read_mostly = {
 219         .name = "workqueues",
 220         .stat_start = workqueue_stat_start,
 221         .stat_next = workqueue_stat_next,
 222         .stat_show = workqueue_stat_show,
 223         .stat_headers = workqueue_stat_headers
 224 };
 225
 226
 227 int __init stat_workqueue_init(void)
 228 {
 229         if (register_stat_tracer(&workqueue_stats)) {
 230                 pr_warning("Unable to register workqueue stat tracer\n");
 231                 return 1;
 232         }
 233
 234         return 0;
 235 }
 236 fs_initcall(stat_workqueue_init);
 237
 238 /*
 239  * Workqueues are created very early, just after pre-smp initcalls.
 240  * So we must register our tracepoints at this stage.
 241  */
 242 int __init trace_workqueue_early_init(void)
 243 {
 244         int ret, cpu;
 245
 246         ret = register_trace_workqueue_insertion(probe_workqueue_insertion);
 247         if (ret)
 248                 goto out;
 249
 250         ret = register_trace_workqueue_execution(probe_workqueue_execution);
 251         if (ret)
 252                 goto no_insertion;
 253
 254         ret = register_trace_workqueue_creation(probe_workqueue_creation);
 255         if (ret)
 256                 goto no_execution;
 257
 258         ret = register_trace_workqueue_destruction(probe_workqueue_destruction);
 259         if (ret)
 260                 goto no_creation;
 261
 262         for_each_possible_cpu(cpu) {
 263                 spin_lock_init(&workqueue_cpu_stat(cpu)->lock);
 264                 INIT_LIST_HEAD(&workqueue_cpu_stat(cpu)->list);
 265         }
 266
 267         return 0;
 268
 269 no_creation:
 270         unregister_trace_workqueue_creation(probe_workqueue_creation);
 271 no_execution:
 272         unregister_trace_workqueue_execution(probe_workqueue_execution);
 273 no_insertion:
 274         unregister_trace_workqueue_insertion(probe_workqueue_insertion);
 275 out:
 276         pr_warning("trace_workqueue: unable to trace workqueues\n");
 277
 278         return 1;
 279 }
 280 early_initcall(trace_workqueue_early_init);