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 "qerror.h"
  18 #include "qemu-timer.h"
  19 #include "trace.h"
  20
  21 /** Trace file header event ID */
  22 #define HEADER_EVENT_ID (~(uint64_t)0) /* avoids conflicting with TraceEventIDs */
  23
  24 /** Trace file magic number */
  25 #define HEADER_MAGIC 0xf2b177cb0aa429b4ULL
  26
  27 /** Trace file version number, bump if format changes */
  28 #define HEADER_VERSION 0
  29
  30 /** Records were dropped event ID */
  31 #define DROPPED_EVENT_ID (~(uint64_t)0 - 1)
  32
  33 /** Trace record is valid */
  34 #define TRACE_RECORD_VALID ((uint64_t)1 << 63)
  35
  36 /** Trace buffer entry */
  37 typedef struct {
  38     uint64_t event;
  39     uint64_t timestamp_ns;
  40     uint64_t x1;
  41     uint64_t x2;
  42     uint64_t x3;
  43     uint64_t x4;
  44     uint64_t x5;
  45     uint64_t x6;
  46 } TraceRecord;
  47
  48 enum {
  49     TRACE_BUF_LEN = 4096,
  50     TRACE_BUF_FLUSH_THRESHOLD = TRACE_BUF_LEN / 4,
  51 };
  52
  53 /*
  54  * Trace records are written out by a dedicated thread.  The thread waits for
  55  * records to become available, writes them out, and then waits again.
  56  */
  57 static pthread_mutex_t trace_lock = PTHREAD_MUTEX_INITIALIZER;
  58 static pthread_cond_t trace_available_cond = PTHREAD_COND_INITIALIZER;
  59 static pthread_cond_t trace_empty_cond = PTHREAD_COND_INITIALIZER;
  60 static bool trace_available;
  61 static bool trace_writeout_enabled;
  62
  63 static TraceRecord trace_buf[TRACE_BUF_LEN];
  64 static unsigned int trace_idx;
  65 static FILE *trace_fp;
  66 static char *trace_file_name = NULL;
  67
  68 /**
  69  * Read a trace record from the trace buffer
  70  *
  71  * @idx         Trace buffer index
  72  * @record      Trace record to fill
  73  *
  74  * Returns false if the record is not valid.
  75  */
  76 static bool get_trace_record(unsigned int idx, TraceRecord *record)
  77 {
  78     if (!(trace_buf[idx].event & TRACE_RECORD_VALID)) {
  79         return false;
  80     }
  81
  82     __sync_synchronize(); /* read memory barrier before accessing record */
  83
  84     *record = trace_buf[idx];
  85     record->event &= ~TRACE_RECORD_VALID;
  86     return true;
  87 }
  88
  89 /**
  90  * Kick writeout thread
  91  *
  92  * @wait        Whether to wait for writeout thread to complete
  93  */
  94 static void flush_trace_file(bool wait)
  95 {
  96     pthread_mutex_lock(&trace_lock);
  97     trace_available = true;
  98     pthread_cond_signal(&trace_available_cond);
  99
 100     if (wait) {
 101         pthread_cond_wait(&trace_empty_cond, &trace_lock);
 102     }
 103
 104     pthread_mutex_unlock(&trace_lock);
 105 }
 106
 107 static void wait_for_trace_records_available(void)
 108 {
 109     pthread_mutex_lock(&trace_lock);
 110     while (!(trace_available && trace_writeout_enabled)) {
 111         pthread_cond_signal(&trace_empty_cond);
 112         pthread_cond_wait(&trace_available_cond, &trace_lock);
 113     }
 114     trace_available = false;
 115     pthread_mutex_unlock(&trace_lock);
 116 }
 117
 118 static void *writeout_thread(void *opaque)
 119 {
 120     TraceRecord record;
 121     unsigned int writeout_idx = 0;
 122     unsigned int num_available, idx;
 123     size_t unused;
 124
 125     for (;;) {
 126         wait_for_trace_records_available();
 127
 128         num_available = trace_idx - writeout_idx;
 129         if (num_available > TRACE_BUF_LEN) {
 130             record = (TraceRecord){
 131                 .event = DROPPED_EVENT_ID,
 132                 .x1 = num_available,
 133             };
 134             unused = fwrite(&record, sizeof(record), 1, trace_fp);
 135             writeout_idx += num_available;
 136         }
 137
 138         idx = writeout_idx % TRACE_BUF_LEN;
 139         while (get_trace_record(idx, &record)) {
 140             trace_buf[idx].event = 0; /* clear valid bit */
 141             unused = fwrite(&record, sizeof(record), 1, trace_fp);
 142             idx = ++writeout_idx % TRACE_BUF_LEN;
 143         }
 144
 145         fflush(trace_fp);
 146     }
 147     return NULL;
 148 }
 149
 150 static void trace(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3,
 151                   uint64_t x4, uint64_t x5, uint64_t x6)
 152 {
 153     unsigned int idx;
 154     uint64_t timestamp;
 155
 156     if (!trace_list[event].state) {
 157         return;
 158     }
 159
 160     timestamp = get_clock();
 161
 162     idx = __sync_fetch_and_add(&trace_idx, 1) % TRACE_BUF_LEN;
 163     trace_buf[idx] = (TraceRecord){
 164         .event = event,
 165         .timestamp_ns = timestamp,
 166         .x1 = x1,
 167         .x2 = x2,
 168         .x3 = x3,
 169         .x4 = x4,
 170         .x5 = x5,
 171         .x6 = x6,
 172     };
 173     __sync_synchronize(); /* write barrier before marking as valid */
 174     trace_buf[idx].event |= TRACE_RECORD_VALID;
 175
 176     if ((idx + 1) % TRACE_BUF_FLUSH_THRESHOLD == 0) {
 177         flush_trace_file(false);
 178     }
 179 }
 180
 181 void trace0(TraceEventID event)
 182 {
 183     trace(event, 0, 0, 0, 0, 0, 0);
 184 }
 185
 186 void trace1(TraceEventID event, uint64_t x1)
 187 {
 188     trace(event, x1, 0, 0, 0, 0, 0);
 189 }
 190
 191 void trace2(TraceEventID event, uint64_t x1, uint64_t x2)
 192 {
 193     trace(event, x1, x2, 0, 0, 0, 0);
 194 }
 195
 196 void trace3(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3)
 197 {
 198     trace(event, x1, x2, x3, 0, 0, 0);
 199 }
 200
 201 void trace4(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4)
 202 {
 203     trace(event, x1, x2, x3, x4, 0, 0);
 204 }
 205
 206 void trace5(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5)
 207 {
 208     trace(event, x1, x2, x3, x4, x5, 0);
 209 }
 210
 211 void trace6(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5, uint64_t x6)
 212 {
 213     trace(event, x1, x2, x3, x4, x5, x6);
 214 }
 215
 216 void st_set_trace_file_enabled(bool enable)
 217 {
 218     if (enable == !!trace_fp) {
 219         return; /* no change */
 220     }
 221
 222     /* Halt trace writeout */
 223     flush_trace_file(true);
 224     trace_writeout_enabled = false;
 225     flush_trace_file(true);
 226
 227     if (enable) {
 228         static const TraceRecord header = {
 229             .event = HEADER_EVENT_ID,
 230             .timestamp_ns = HEADER_MAGIC,
 231             .x1 = HEADER_VERSION,
 232         };
 233
 234         trace_fp = fopen(trace_file_name, "w");
 235         if (!trace_fp) {
 236             return;
 237         }
 238
 239         if (fwrite(&header, sizeof header, 1, trace_fp) != 1) {
 240             fclose(trace_fp);
 241             trace_fp = NULL;
 242             return;
 243         }
 244
 245         /* Resume trace writeout */
 246         trace_writeout_enabled = true;
 247         flush_trace_file(false);
 248     } else {
 249         fclose(trace_fp);
 250         trace_fp = NULL;
 251     }
 252 }
 253
 254 /**
 255  * Set the name of a trace file
 256  *
 257  * @file        The trace file name or NULL for the default name-<pid> set at
 258  *              config time
 259  */
 260 bool st_set_trace_file(const char *file)
 261 {
 262     st_set_trace_file_enabled(false);
 263
 264     free(trace_file_name);
 265
 266     if (!file) {
 267         if (asprintf(&trace_file_name, CONFIG_TRACE_FILE, getpid()) < 0) {
 268             trace_file_name = NULL;
 269             return false;
 270         }
 271     } else {
 272         if (asprintf(&trace_file_name, "%s", file) < 0) {
 273             trace_file_name = NULL;
 274             return false;
 275         }
 276     }
 277
 278     st_set_trace_file_enabled(true);
 279     return true;
 280 }
 281
 282 void st_print_trace_file_status(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
 283 {
 284     stream_printf(stream, "Trace file \"%s\" %s.\n",
 285                   trace_file_name, trace_fp ? "on" : "off");
 286 }
 287
 288 void st_print_trace(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
 289 {
 290     unsigned int i;
 291
 292     for (i = 0; i < TRACE_BUF_LEN; i++) {
 293         TraceRecord record;
 294
 295         if (!get_trace_record(i, &record)) {
 296             continue;
 297         }
 298         stream_printf(stream, "Event %" PRIu64 " : %" PRIx64 " %" PRIx64
 299                       " %" PRIx64 " %" PRIx64 " %" PRIx64 " %" PRIx64 "\n",
 300                       record.event, record.x1, record.x2,
 301                       record.x3, record.x4, record.x5,
 302                       record.x6);
 303     }
 304 }
 305
 306 void st_print_trace_events(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
 307 {
 308     unsigned int i;
 309
 310     for (i = 0; i < NR_TRACE_EVENTS; i++) {
 311         stream_printf(stream, "%s [Event ID %u] : state %u\n",
 312                       trace_list[i].tp_name, i, trace_list[i].state);
 313     }
 314 }
 315
 316 bool st_change_trace_event_state(const char *name, bool enabled)
 317 {
 318     unsigned int i;
 319
 320     for (i = 0; i < NR_TRACE_EVENTS; i++) {
 321         if (!strcmp(trace_list[i].tp_name, name)) {
 322             trace_list[i].state = enabled;
 323             return true;
 324         }
 325     }
 326     return false;
 327 }
 328
 329 void st_flush_trace_buffer(void)
 330 {
 331     flush_trace_file(true);
 332 }
 333
 334 void st_init(const char *file)
 335 {
 336     pthread_t thread;
 337     pthread_attr_t attr;
 338     sigset_t set, oldset;
 339     int ret;
 340
 341     pthread_attr_init(&attr);
 342     pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
 343
 344     sigfillset(&set);
 345     pthread_sigmask(SIG_SETMASK, &set, &oldset);
 346     ret = pthread_create(&thread, &attr, writeout_thread, NULL);
 347     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
 348
 349     if (ret != 0) {
 350         error_report("warning: unable to create trace file thread\n");
 351         return;
 352     }
 353
 354     atexit(st_flush_trace_buffer);
 355     st_set_trace_file(file);
 356 }