#include <stdint.h>
#include <stdio.h>
#include <time.h>
+#include <signal.h>
+#include <pthread.h>
+#include "qemu-timer.h"
#include "trace.h"
/** Trace file header event ID */
/** Trace file version number, bump if format changes */
#define HEADER_VERSION 0
+/** Records were dropped event ID */
+#define DROPPED_EVENT_ID (~(uint64_t)0 - 1)
+
+/** Trace record is valid */
+#define TRACE_RECORD_VALID ((uint64_t)1 << 63)
+
/** Trace buffer entry */
typedef struct {
uint64_t event;
} TraceRecord;
enum {
- TRACE_BUF_LEN = 64 * 1024 / sizeof(TraceRecord),
+ TRACE_BUF_LEN = 4096,
+ TRACE_BUF_FLUSH_THRESHOLD = TRACE_BUF_LEN / 4,
};
+/*
+ * Trace records are written out by a dedicated thread. The thread waits for
+ * records to become available, writes them out, and then waits again.
+ */
+static pthread_mutex_t trace_lock = PTHREAD_MUTEX_INITIALIZER;
+static pthread_cond_t trace_available_cond = PTHREAD_COND_INITIALIZER;
+static pthread_cond_t trace_empty_cond = PTHREAD_COND_INITIALIZER;
+static bool trace_available;
+static bool trace_writeout_enabled;
+
static TraceRecord trace_buf[TRACE_BUF_LEN];
static unsigned int trace_idx;
static FILE *trace_fp;
static char *trace_file_name = NULL;
-static bool trace_file_enabled = false;
-
-void st_print_trace_file_status(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
-{
- stream_printf(stream, "Trace file \"%s\" %s.\n",
- trace_file_name, trace_file_enabled ? "on" : "off");
-}
-
-static bool write_header(FILE *fp)
-{
- static const TraceRecord header = {
- .event = HEADER_EVENT_ID,
- .timestamp_ns = HEADER_MAGIC,
- .x1 = HEADER_VERSION,
- };
-
- return fwrite(&header, sizeof header, 1, fp) == 1;
-}
/**
- * set_trace_file : To set the name of a trace file.
- * @file : pointer to the name to be set.
- * If NULL, set to the default name-<pid> set at config time.
+ * Read a trace record from the trace buffer
+ *
+ * @idx Trace buffer index
+ * @record Trace record to fill
+ *
+ * Returns false if the record is not valid.
*/
-bool st_set_trace_file(const char *file)
+static bool get_trace_record(unsigned int idx, TraceRecord *record)
{
- st_set_trace_file_enabled(false);
-
- free(trace_file_name);
-
- if (!file) {
- if (asprintf(&trace_file_name, CONFIG_TRACE_FILE, getpid()) < 0) {
- trace_file_name = NULL;
- return false;
- }
- } else {
- if (asprintf(&trace_file_name, "%s", file) < 0) {
- trace_file_name = NULL;
- return false;
- }
+ if (!(trace_buf[idx].event & TRACE_RECORD_VALID)) {
+ return false;
}
- st_set_trace_file_enabled(true);
+ __sync_synchronize(); /* read memory barrier before accessing record */
+
+ *record = trace_buf[idx];
+ record->event &= ~TRACE_RECORD_VALID;
return true;
}
-static void flush_trace_file(void)
+/**
+ * Kick writeout thread
+ *
+ * @wait Whether to wait for writeout thread to complete
+ */
+static void flush_trace_file(bool wait)
{
- /* If the trace file is not open yet, open it now */
- if (!trace_fp) {
- trace_fp = fopen(trace_file_name, "w");
- if (!trace_fp) {
- /* Avoid repeatedly trying to open file on failure */
- trace_file_enabled = false;
- return;
- }
- write_header(trace_fp);
- }
+ pthread_mutex_lock(&trace_lock);
+ trace_available = true;
+ pthread_cond_signal(&trace_available_cond);
- if (trace_fp) {
- size_t unused; /* for when fwrite(3) is declared warn_unused_result */
- unused = fwrite(trace_buf, trace_idx * sizeof(trace_buf[0]), 1, trace_fp);
+ if (wait) {
+ pthread_cond_wait(&trace_empty_cond, &trace_lock);
}
+
+ pthread_mutex_unlock(&trace_lock);
}
-void st_flush_trace_buffer(void)
+static void wait_for_trace_records_available(void)
{
- if (trace_file_enabled) {
- flush_trace_file();
+ pthread_mutex_lock(&trace_lock);
+ while (!(trace_available && trace_writeout_enabled)) {
+ pthread_cond_signal(&trace_empty_cond);
+ pthread_cond_wait(&trace_available_cond, &trace_lock);
}
-
- /* Discard written trace records */
- trace_idx = 0;
+ trace_available = false;
+ pthread_mutex_unlock(&trace_lock);
}
-void st_set_trace_file_enabled(bool enable)
+static void *writeout_thread(void *opaque)
{
- if (enable == trace_file_enabled) {
- return; /* no change */
- }
+ TraceRecord record;
+ unsigned int writeout_idx = 0;
+ unsigned int num_available, idx;
+ size_t unused __attribute__ ((unused));
+
+ for (;;) {
+ wait_for_trace_records_available();
+
+ num_available = trace_idx - writeout_idx;
+ if (num_available > TRACE_BUF_LEN) {
+ record = (TraceRecord){
+ .event = DROPPED_EVENT_ID,
+ .x1 = num_available,
+ };
+ unused = fwrite(&record, sizeof(record), 1, trace_fp);
+ writeout_idx += num_available;
+ }
- /* Flush/discard trace buffer */
- st_flush_trace_buffer();
+ idx = writeout_idx % TRACE_BUF_LEN;
+ while (get_trace_record(idx, &record)) {
+ trace_buf[idx].event = 0; /* clear valid bit */
+ unused = fwrite(&record, sizeof(record), 1, trace_fp);
+ idx = ++writeout_idx % TRACE_BUF_LEN;
+ }
- /* To disable, close trace file */
- if (!enable) {
- fclose(trace_fp);
- trace_fp = NULL;
+ fflush(trace_fp);
}
-
- trace_file_enabled = enable;
+ return NULL;
}
static void trace(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3,
uint64_t x4, uint64_t x5, uint64_t x6)
{
- TraceRecord *rec = &trace_buf[trace_idx];
- struct timespec ts;
-
- /* TODO Windows? It would be good to use qemu-timer here but that isn't
- * linked into qemu-tools. Also we should avoid recursion in the tracing
- * code, therefore it is useful to be self-contained.
- */
- clock_gettime(CLOCK_MONOTONIC, &ts);
+ unsigned int idx;
+ uint64_t timestamp;
if (!trace_list[event].state) {
return;
}
- rec->event = event;
- rec->timestamp_ns = ts.tv_sec * 1000000000LL + ts.tv_nsec;
- rec->x1 = x1;
- rec->x2 = x2;
- rec->x3 = x3;
- rec->x4 = x4;
- rec->x5 = x5;
- rec->x6 = x6;
-
- if (++trace_idx == TRACE_BUF_LEN) {
- st_flush_trace_buffer();
+ timestamp = get_clock();
+
+ idx = __sync_fetch_and_add(&trace_idx, 1) % TRACE_BUF_LEN;
+ trace_buf[idx] = (TraceRecord){
+ .event = event,
+ .timestamp_ns = timestamp,
+ .x1 = x1,
+ .x2 = x2,
+ .x3 = x3,
+ .x4 = x4,
+ .x5 = x5,
+ .x6 = x6,
+ };
+ __sync_synchronize(); /* write barrier before marking as valid */
+ trace_buf[idx].event |= TRACE_RECORD_VALID;
+
+ if ((idx + 1) % TRACE_BUF_FLUSH_THRESHOLD == 0) {
+ flush_trace_file(false);
}
}
trace(event, x1, x2, x3, x4, x5, x6);
}
+void st_set_trace_file_enabled(bool enable)
+{
+ if (enable == !!trace_fp) {
+ return; /* no change */
+ }
+
+ /* Halt trace writeout */
+ flush_trace_file(true);
+ trace_writeout_enabled = false;
+ flush_trace_file(true);
+
+ if (enable) {
+ static const TraceRecord header = {
+ .event = HEADER_EVENT_ID,
+ .timestamp_ns = HEADER_MAGIC,
+ .x1 = HEADER_VERSION,
+ };
+
+ trace_fp = fopen(trace_file_name, "w");
+ if (!trace_fp) {
+ return;
+ }
+
+ if (fwrite(&header, sizeof header, 1, trace_fp) != 1) {
+ fclose(trace_fp);
+ trace_fp = NULL;
+ return;
+ }
+
+ /* Resume trace writeout */
+ trace_writeout_enabled = true;
+ flush_trace_file(false);
+ } else {
+ fclose(trace_fp);
+ trace_fp = NULL;
+ }
+}
+
/**
- * Flush the trace buffer on exit
+ * Set the name of a trace file
+ *
+ * @file The trace file name or NULL for the default name-<pid> set at
+ * config time
*/
-static void __attribute__((constructor)) st_init(void)
+bool st_set_trace_file(const char *file)
{
- atexit(st_flush_trace_buffer);
+ st_set_trace_file_enabled(false);
+
+ free(trace_file_name);
+
+ if (!file) {
+ if (asprintf(&trace_file_name, CONFIG_TRACE_FILE, getpid()) < 0) {
+ trace_file_name = NULL;
+ return false;
+ }
+ } else {
+ if (asprintf(&trace_file_name, "%s", file) < 0) {
+ trace_file_name = NULL;
+ return false;
+ }
+ }
+
+ st_set_trace_file_enabled(true);
+ return true;
+}
+
+void st_print_trace_file_status(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
+{
+ stream_printf(stream, "Trace file \"%s\" %s.\n",
+ trace_file_name, trace_fp ? "on" : "off");
}
void st_print_trace(FILE *stream, int (*stream_printf)(FILE *stream, const char *fmt, ...))
{
unsigned int i;
- for (i = 0; i < trace_idx; i++) {
- stream_printf(stream, "Event %lu : %lx %lx %lx %lx %lx\n",
- trace_buf[i].event, trace_buf[i].x1, trace_buf[i].x2,
- trace_buf[i].x3, trace_buf[i].x4, trace_buf[i].x5);
+ for (i = 0; i < TRACE_BUF_LEN; i++) {
+ TraceRecord record;
+
+ if (!get_trace_record(i, &record)) {
+ continue;
+ }
+ stream_printf(stream, "Event %" PRIu64 " : %" PRIx64 " %" PRIx64
+ " %" PRIx64 " %" PRIx64 " %" PRIx64 " %" PRIx64 "\n",
+ record.event, record.x1, record.x2,
+ record.x3, record.x4, record.x5,
+ record.x6);
}
}
}
}
-static TraceEvent* find_trace_event_by_name(const char *tname)
+bool st_change_trace_event_state(const char *name, bool enabled)
{
unsigned int i;
- if (!tname) {
- return NULL;
- }
-
for (i = 0; i < NR_TRACE_EVENTS; i++) {
- if (!strcmp(trace_list[i].tp_name, tname)) {
- return &trace_list[i];
+ if (!strcmp(trace_list[i].tp_name, name)) {
+ trace_list[i].state = enabled;
+ return true;
}
}
- return NULL; /* indicates end of list reached without a match */
+ return false;
+}
+
+void st_flush_trace_buffer(void)
+{
+ flush_trace_file(true);
}
-void st_change_trace_event_state(const char *tname, bool tstate)
+bool st_init(const char *file)
{
- TraceEvent *tp;
+ pthread_t thread;
+ pthread_attr_t attr;
+ sigset_t set, oldset;
+ int ret;
+
+ pthread_attr_init(&attr);
+ pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
+
+ sigfillset(&set);
+ pthread_sigmask(SIG_SETMASK, &set, &oldset);
+ ret = pthread_create(&thread, &attr, writeout_thread, NULL);
+ pthread_sigmask(SIG_SETMASK, &oldset, NULL);
- tp = find_trace_event_by_name(tname);
- if (tp) {
- tp->state = tstate;
+ if (ret != 0) {
+ return false;
}
+
+ atexit(st_flush_trace_buffer);
+ st_set_trace_file(file);
+ return true;
}
projects / qemu.git / blobdiff