simpletrace.c

   1 /*
   2  * Simple trace backend
   3  *
   4  * Copyright IBM, Corp. 2010
   5  *
   6  * This work is licensed under the terms of the GNU GPL, version 2.  See
   7  * the COPYING file in the top-level directory.
   8  *
   9  */
  10
  11 #include <stdlib.h>
  12 #include <stdint.h>
  13 #include <stdio.h>
  14 #include <time.h>
  15 #include <signal.h>
  16 #include <pthread.h>
  17 #include "qemu-timer.h"
  18 #include "trace.h"
  19
  20 /** Trace file header event ID */
  21 #define HEADER_EVENT_ID (~(uint64_t)0) /* avoids conflicting with TraceEventIDs */
  22
  23 /** Trace file magic number */
  24 #define HEADER_MAGIC 0xf2b177cb0aa429b4ULL
  25
  26 /** Trace file version number, bump if format changes */
  27 #define HEADER_VERSION 0
  28
  29 /** Records were dropped event ID */
  30 #define DROPPED_EVENT_ID (~(uint64_t)0 - 1)
  31
  32 /** Trace record is valid */
  33 #define TRACE_RECORD_VALID ((uint64_t)1 << 63)
  34
  35 /** Trace buffer entry */
  36 typedef struct {
  37     uint64_t event;
  38     uint64_t timestamp_ns;
  39     uint64_t x1;
  40     uint64_t x2;
  41     uint64_t x3;
  42     uint64_t x4;
  43     uint64_t x5;
  44     uint64_t x6;
  45 } TraceRecord;
  46
  47 enum {
  48     TRACE_BUF_LEN = 4096,
  49     TRACE_BUF_FLUSH_THRESHOLD = TRACE_BUF_LEN / 4,
  50 };
  51
  52 /*
  53  * Trace records are written out by a dedicated thread.  The thread waits for
  54  * records to become available, writes them out, and then waits again.
  55  */
  56 static pthread_mutex_t trace_lock = PTHREAD_MUTEX_INITIALIZER;
  57 static pthread_cond_t trace_available_cond = PTHREAD_COND_INITIALIZER;
  58 static pthread_cond_t trace_empty_cond = PTHREAD_COND_INITIALIZER;
  59 static bool trace_available;
  60 static bool trace_writeout_enabled;
  61
  62 static TraceRecord trace_buf[TRACE_BUF_LEN];
  63 static unsigned int trace_idx;
  64 static FILE *trace_fp;
  65 static char *trace_file_name = NULL;
  66
  67 /**
  68  * Read a trace record from the trace buffer
  69  *
  70  * @idx         Trace buffer index
  71  * @record      Trace record to fill
  72  *
  73  * Returns false if the record is not valid.
  74  */
  75 static bool get_trace_record(unsigned int idx, TraceRecord *record)
  76 {
  77     if (!(trace_buf[idx].event & TRACE_RECORD_VALID)) {
  78         return false;
  79     }
  80
  81     __sync_synchronize(); /* read memory barrier before accessing record */
  82
  83     *record = trace_buf[idx];
  84     record->event &= ~TRACE_RECORD_VALID;
  85     return true;
  86 }
  87
  88 /**
  89  * Kick writeout thread
  90  *
  91  * @wait        Whether to wait for writeout thread to complete
  92  */
  93 static void flush_trace_file(bool wait)
  94 {
  95     pthread_mutex_lock(&trace_lock);
  96     trace_available = true;
  97     pthread_cond_signal(&trace_available_cond);
  98
  99     if (wait) {
 100         pthread_cond_wait(&trace_empty_cond, &trace_lock);
 101     }
 102
 103     pthread_mutex_unlock(&trace_lock);
 104 }
 105
 106 static void wait_for_trace_records_available(void)
 107 {
 108     pthread_mutex_lock(&trace_lock);
 109     while (!(trace_available && trace_writeout_enabled)) {
 110         pthread_cond_signal(&trace_empty_cond);
 111         pthread_cond_wait(&trace_available_cond, &trace_lock);
 112     }
 113     trace_available = false;
 114     pthread_mutex_unlock(&trace_lock);
 115 }
 116
 117 static void *writeout_thread(void *opaque)
 118 {
 119     TraceRecord record;
 120     unsigned int writeout_idx = 0;
 121     unsigned int num_available, idx;
 122     size_t unused;
 123
 124     for (;;) {
 125         wait_for_trace_records_available();
 126
 127         num_available = trace_idx - writeout_idx;
 128         if (num_available > TRACE_BUF_LEN) {
 129             record = (TraceRecord){
 130                 .event = DROPPED_EVENT_ID,
 131                 .x1 = num_available,
 132             };
 133             unused = fwrite(&record, sizeof(record), 1, trace_fp);
 134             writeout_idx += num_available;
 135         }
 136
 137         idx = writeout_idx % TRACE_BUF_LEN;
 138         while (get_trace_record(idx, &record)) {
 139             trace_buf[idx].event = 0; /* clear valid bit */
 140             unused = fwrite(&record, sizeof(record), 1, trace_fp);
 141             idx = ++writeout_idx % TRACE_BUF_LEN;
 142         }
 143
 144         fflush(trace_fp);
 145     }
 146     return NULL;
 147 }
 148
 149 static void trace(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3,
 150                   uint64_t x4, uint64_t x5, uint64_t x6)
 151 {
 152     unsigned int idx;
 153     uint64_t timestamp;
 154
 155     if (!trace_list[event].state) {
 156         return;
 157     }
 158
 159     timestamp = get_clock();
 160
 161     idx = __sync_fetch_and_add(&trace_idx, 1) % TRACE_BUF_LEN;
 162     trace_buf[idx] = (TraceRecord){
 163         .event = event,
 164         .timestamp_ns = timestamp,
 165         .x1 = x1,
 166         .x2 = x2,
 167         .x3 = x3,
 168         .x4 = x4,
 169         .x5 = x5,
 170         .x6 = x6,
 171     };
 172     __sync_synchronize(); /* write barrier before marking as valid */
 173     trace_buf[idx].event |= TRACE_RECORD_VALID;
 174
 175     if ((idx + 1) % TRACE_BUF_FLUSH_THRESHOLD == 0) {
 176         flush_trace_file(false);
 177     }
 178 }
 179
 180 void trace0(TraceEventID event)
 181 {
 182     trace(event, 0, 0, 0, 0, 0, 0);
 183 }
 184
 185 void trace1(TraceEventID event, uint64_t x1)
 186 {
 187     trace(event, x1, 0, 0, 0, 0, 0);
 188 }
 189
 190 void trace2(TraceEventID event, uint64_t x1, uint64_t x2)
 191 {
 192     trace(event, x1, x2, 0, 0, 0, 0);
 193 }
 194
 195 void trace3(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3)
 196 {
 197     trace(event, x1, x2, x3, 0, 0, 0);
 198 }
 199
 200 void trace4(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4)
 201 {
 202     trace(event, x1, x2, x3, x4, 0, 0);
 203 }
 204
 205 void trace5(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5)
 206 {
 207     trace(event, x1, x2, x3, x4, x5, 0);
 208 }
 209
 210 void trace6(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5, uint64_t x6)
 211 {
 212     trace(event, x1, x2, x3, x4, x5, x6);
 213 }
 214
 215 void st_set_trace_file_enabled(bool enable)
 216 {
 217     if (enable == !!trace_fp) {
 218         return; /* no change */
 219     }
 220
 221     /* Halt trace writeout */
 222     flush_trace_file(true);
 223     trace_writeout_enabled = false;
 224     flush_trace_file(true);
 225
 226     if (enable) {
 227         static const TraceRecord header = {
 228             .event = HEADER_EVENT_ID,
 229             .timestamp_ns = HEADER_MAGIC,
 230             .x1 = HEADER_VERSION,
 231         };
 232
 233         trace_fp = fopen(trace_file_name, "w");
 234         if (!trace_fp) {
 235             return;
 236         }
 237
 238         if (fwrite(&header, sizeof header, 1, trace_fp) != 1) {
 239             fclose(trace_fp);
 240             trace_fp = NULL;
 241             return;
 242         }
 243
 244         /* Resume trace writeout */
 245         trace_writeout_enabled = true;
 246         flush_trace_file(false);
 247     } else {
 248         fclose(trace_fp);
 249         trace_fp = NULL;
 250     }
 251 }
 252
 253 /**
 254  * Set the name of a trace file
 255  *
 256  * @file        The trace file name or NULL for the default name-<pid> set at
 257  *              config time
 258  */
 259 bool st_set_trace_file(const char *file)
 260 {
 261     st_set_trace_file_enabled(false);
 262
 263     free(trace_file_name);
 264
 265     if (!file) {
 266         if (asprintf(&trace_file_name, CONFIG_TRACE_FILE, getpid()) < 0) {
 267             trace_file_name = NULL;
 268             return false;
 269         }
 270     } else {
 271         if (asprintf(&trace_file_name, "%s", file) < 0) {
 272             trace_file_name = NULL;
 273             return false;
 274         }
 275     }
 276
 277     st_set_trace_file_enabled(true);
 278     return true;
 279 }
 280
 281 void st_print_trace_file_status(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
 282 {
 283     stream_printf(stream, "Trace file \"%s\" %s.\n",
 284                   trace_file_name, trace_fp ? "on" : "off");
 285 }
 286
 287 void st_print_trace(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
 288 {
 289     unsigned int i;
 290
 291     for (i = 0; i < TRACE_BUF_LEN; i++) {
 292         TraceRecord record;
 293
 294         if (!get_trace_record(i, &record)) {
 295             continue;
 296         }
 297         stream_printf(stream, "Event %" PRIu64 " : %" PRIx64 " %" PRIx64
 298                       " %" PRIx64 " %" PRIx64 " %" PRIx64 " %" PRIx64 "\n",
 299                       record.event, record.x1, record.x2,
 300                       record.x3, record.x4, record.x5,
 301                       record.x6);
 302     }
 303 }
 304
 305 void st_print_trace_events(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
 306 {
 307     unsigned int i;
 308
 309     for (i = 0; i < NR_TRACE_EVENTS; i++) {
 310         stream_printf(stream, "%s [Event ID %u] : state %u\n",
 311                       trace_list[i].tp_name, i, trace_list[i].state);
 312     }
 313 }
 314
 315 bool st_change_trace_event_state(const char *name, bool enabled)
 316 {
 317     unsigned int i;
 318
 319     for (i = 0; i < NR_TRACE_EVENTS; i++) {
 320         if (!strcmp(trace_list[i].tp_name, name)) {
 321             trace_list[i].state = enabled;
 322             return true;
 323         }
 324     }
 325     return false;
 326 }
 327
 328 void st_flush_trace_buffer(void)
 329 {
 330     flush_trace_file(true);
 331 }
 332
 333 bool st_init(const char *file)
 334 {
 335     pthread_t thread;
 336     pthread_attr_t attr;
 337     sigset_t set, oldset;
 338     int ret;
 339
 340     pthread_attr_init(&attr);
 341     pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
 342
 343     sigfillset(&set);
 344     pthread_sigmask(SIG_SETMASK, &set, &oldset);
 345     ret = pthread_create(&thread, &attr, writeout_thread, NULL);
 346     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 347
 348     if (ret != 0) {
 349         return false;
 350     }
 351
 352     atexit(st_flush_trace_buffer);
 353     st_set_trace_file(file);
 354     return true;
 355 }