[qemu.git] / trace / simple.c

/*
 * Simple trace backend
 *
 * Copyright IBM, Corp. 2010
 *
 * This work is licensed under the terms of the GNU GPL, version 2.  See
 * the COPYING file in the top-level directory.
 *
 */

#include <stdlib.h>
#include <stdint.h>
#include <stdio.h>
#include <time.h>
#ifndef _WIN32
#include <signal.h>
#include <pthread.h>
#endif
#include "qemu-timer.h"
#include "trace.h"
#include "trace/control.h"

/** Trace file header event ID */
#define HEADER_EVENT_ID (~(uint64_t)0) /* avoids conflicting with TraceEventIDs */

/** Trace file magic number */
#define HEADER_MAGIC 0xf2b177cb0aa429b4ULL

/** 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;
    uint64_t timestamp_ns;
    uint64_t x1;
    uint64_t x2;
    uint64_t x3;
    uint64_t x4;
    uint64_t x5;
    uint64_t x6;
} TraceRecord;

enum {
    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 GStaticMutex trace_lock = G_STATIC_MUTEX_INIT;
static GCond *trace_available_cond;
static GCond *trace_empty_cond;
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;

/**
 * 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.
 */
static bool get_trace_record(unsigned int idx, TraceRecord *record)
{
    if (!(trace_buf[idx].event & TRACE_RECORD_VALID)) {
        return false;
    }

    __sync_synchronize(); /* read memory barrier before accessing record */

    *record = trace_buf[idx];
    record->event &= ~TRACE_RECORD_VALID;
    return true;
}

/**
 * Kick writeout thread
 *
 * @wait        Whether to wait for writeout thread to complete
 */
static void flush_trace_file(bool wait)
{
    g_static_mutex_lock(&trace_lock);
    trace_available = true;
    g_cond_signal(trace_available_cond);

    if (wait) {
        g_cond_wait(trace_empty_cond, g_static_mutex_get_mutex(&trace_lock));
    }

    g_static_mutex_unlock(&trace_lock);
}

static void wait_for_trace_records_available(void)
{
    g_static_mutex_lock(&trace_lock);
    while (!(trace_available && trace_writeout_enabled)) {
        g_cond_signal(trace_empty_cond);
        g_cond_wait(trace_available_cond,
                    g_static_mutex_get_mutex(&trace_lock));
    }
    trace_available = false;
    g_static_mutex_unlock(&trace_lock);
}

static gpointer writeout_thread(gpointer opaque)
{
    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;
        }

        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;
        }

        fflush(trace_fp);
    }
    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)
{
    unsigned int idx;
    uint64_t timestamp;

    if (!trace_list[event].state) {
        return;
    }

    timestamp = get_clock();

    idx = g_atomic_int_exchange_and_add((gint *)&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);
    }
}

void trace0(TraceEventID event)
{
    trace(event, 0, 0, 0, 0, 0, 0);
}

void trace1(TraceEventID event, uint64_t x1)
{
    trace(event, x1, 0, 0, 0, 0, 0);
}

void trace2(TraceEventID event, uint64_t x1, uint64_t x2)
{
    trace(event, x1, x2, 0, 0, 0, 0);
}

void trace3(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3)
{
    trace(event, x1, x2, x3, 0, 0, 0);
}

void trace4(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4)
{
    trace(event, x1, x2, x3, x4, 0, 0);
}

void trace5(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5)
{
    trace(event, x1, x2, x3, x4, x5, 0);
}

void trace6(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5, uint64_t x6)
{
    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, "wb");
        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;
    }
}

/**
 * Set the name of a trace file
 *
 * @file        The trace file name or NULL for the default name-<pid> set at
 *              config time
 */
bool st_set_trace_file(const char *file)
{
    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_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);
    }
}

void st_flush_trace_buffer(void)
{
    flush_trace_file(true);
}

void trace_print_events(FILE *stream, fprintf_function stream_printf)
{
    unsigned int i;

    for (i = 0; i < NR_TRACE_EVENTS; i++) {
        stream_printf(stream, "%s [Event ID %u] : state %u\n",
                      trace_list[i].tp_name, i, trace_list[i].state);
    }
}

bool trace_event_set_state(const char *name, bool state)
{
    unsigned int i;
    unsigned int len;
    bool wildcard = false;
    bool matched = false;

    len = strlen(name);
    if (len > 0 && name[len - 1] == '*') {
        wildcard = true;
        len -= 1;
    }
    for (i = 0; i < NR_TRACE_EVENTS; i++) {
        if (wildcard) {
            if (!strncmp(trace_list[i].tp_name, name, len)) {
                trace_list[i].state = state;
                matched = true;
            }
            continue;
        }
        if (!strcmp(trace_list[i].tp_name, name)) {
            trace_list[i].state = state;
            return true;
        }
    }
    return matched;
}

/* Helper function to create a thread with signals blocked.  Use glib's
 * portable threads since QEMU abstractions cannot be used due to reentrancy in
 * the tracer.  Also note the signal masking on POSIX hosts so that the thread
 * does not steal signals when the rest of the program wants them blocked.
 */
static GThread *trace_thread_create(GThreadFunc fn)
{
    GThread *thread;
#ifndef _WIN32
    sigset_t set, oldset;

    sigfillset(&set);
    pthread_sigmask(SIG_SETMASK, &set, &oldset);
#endif
    thread = g_thread_create(writeout_thread, NULL, FALSE, NULL);
#ifndef _WIN32
    pthread_sigmask(SIG_SETMASK, &oldset, NULL);
#endif

    return thread;
}

bool trace_backend_init(const char *events, const char *file)
{
    GThread *thread;

    if (!g_thread_supported()) {
#if !GLIB_CHECK_VERSION(2, 31, 0)
        g_thread_init(NULL);
#else
        fprintf(stderr, "glib threading failed to initialize.\n");
        exit(1);
#endif
    }

    trace_available_cond = g_cond_new();
    trace_empty_cond = g_cond_new();

    thread = trace_thread_create(writeout_thread);
    if (!thread) {
        fprintf(stderr, "warning: unable to initialize simple trace backend\n");
        return false;
    }

    atexit(st_flush_trace_buffer);
    trace_backend_init_events(events);
    st_set_trace_file(file);
    return true;
}
Commit	Line	Data
26f7227b SH	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>
85aff158	15	#ifndef _WIN32
0b5538c3 SH	16	#include <signal.h>
0b5538c3 SH	17	#include <pthread.h>
85aff158	18	#endif
c57c846a	19	#include "qemu-timer.h"
26f7227b	20	#include "trace.h"
e4858974	21	#include "trace/control.h"
26f7227b SH	22
	23	/** Trace file header event ID */
	24	#define HEADER_EVENT_ID (~(uint64_t)0) /* avoids conflicting with TraceEventIDs */
	25
	26	/** Trace file magic number */
	27	#define HEADER_MAGIC 0xf2b177cb0aa429b4ULL
	28
	29	/** Trace file version number, bump if format changes */
	30	#define HEADER_VERSION 0
	31
0b5538c3 SH	32	/** Records were dropped event ID */
	33	#define DROPPED_EVENT_ID (~(uint64_t)0 - 1)
	34
	35	/** Trace record is valid */
	36	#define TRACE_RECORD_VALID ((uint64_t)1 << 63)
	37
26f7227b SH	38	/** Trace buffer entry */
	39	typedef struct {
	40	uint64_t event;
	41	uint64_t timestamp_ns;
	42	uint64_t x1;
	43	uint64_t x2;
	44	uint64_t x3;
	45	uint64_t x4;
	46	uint64_t x5;
	47	uint64_t x6;
	48	} TraceRecord;
	49
	50	enum {
0b5538c3 SH	51	TRACE_BUF_LEN = 4096,
0b5538c3 SH	52	TRACE_BUF_FLUSH_THRESHOLD = TRACE_BUF_LEN / 4,
26f7227b SH	53	};
26f7227b SH	54
0b5538c3 SH	55	/*
	56	* Trace records are written out by a dedicated thread. The thread waits for
	57	* records to become available, writes them out, and then waits again.
	58	*/
85aff158 SH	59	static GStaticMutex trace_lock = G_STATIC_MUTEX_INIT;
	60	static GCond *trace_available_cond;
	61	static GCond *trace_empty_cond;
0b5538c3 SH	62	static bool trace_available;
	63	static bool trace_writeout_enabled;
	64
26f7227b SH	65	static TraceRecord trace_buf[TRACE_BUF_LEN];
	66	static unsigned int trace_idx;
	67	static FILE *trace_fp;
c5ceb523	68	static char *trace_file_name = NULL;
26f7227b	69
c5ceb523	70	/**
0b5538c3 SH	71	* Read a trace record from the trace buffer
	72	*
	73	* @idx Trace buffer index
	74	* @record Trace record to fill
	75	*
	76	* Returns false if the record is not valid.
c5ceb523	77	*/
0b5538c3	78	static bool get_trace_record(unsigned int idx, TraceRecord *record)
9410b56c	79	{
0b5538c3 SH	80	if (!(trace_buf[idx].event & TRACE_RECORD_VALID)) {
0b5538c3 SH	81	return false;
9410b56c PS	82	}
9410b56c PS	83
0b5538c3 SH	84	__sync_synchronize(); /* read memory barrier before accessing record */
	85
	86	*record = trace_buf[idx];
	87	record->event &= ~TRACE_RECORD_VALID;
c5ceb523	88	return true;
9410b56c PS	89	}
9410b56c PS	90
0b5538c3 SH	91	/**
	92	* Kick writeout thread
	93	*
	94	* @wait Whether to wait for writeout thread to complete
	95	*/
	96	static void flush_trace_file(bool wait)
26f7227b	97	{
85aff158	98	g_static_mutex_lock(&trace_lock);
0b5538c3	99	trace_available = true;
85aff158	100	g_cond_signal(trace_available_cond);
c5ceb523	101
0b5538c3	102	if (wait) {
85aff158	103	g_cond_wait(trace_empty_cond, g_static_mutex_get_mutex(&trace_lock));
26f7227b	104	}
0b5538c3	105
85aff158	106	g_static_mutex_unlock(&trace_lock);
c5ceb523 SH	107	}
c5ceb523 SH	108
0b5538c3	109	static void wait_for_trace_records_available(void)
c5ceb523	110	{
85aff158	111	g_static_mutex_lock(&trace_lock);
0b5538c3	112	while (!(trace_available && trace_writeout_enabled)) {
85aff158 SH	113	g_cond_signal(trace_empty_cond);
	114	g_cond_wait(trace_available_cond,
	115	g_static_mutex_get_mutex(&trace_lock));
c5ceb523	116	}
0b5538c3	117	trace_available = false;
85aff158	118	g_static_mutex_unlock(&trace_lock);
26f7227b SH	119	}
26f7227b SH	120
85aff158	121	static gpointer writeout_thread(gpointer opaque)
26f7227b	122	{
0b5538c3 SH	123	TraceRecord record;
	124	unsigned int writeout_idx = 0;
	125	unsigned int num_available, idx;
0caf448b	126	size_t unused __attribute__ ((unused));
0b5538c3 SH	127
	128	for (;;) {
	129	wait_for_trace_records_available();
	130
	131	num_available = trace_idx - writeout_idx;
	132	if (num_available > TRACE_BUF_LEN) {
	133	record = (TraceRecord){
	134	.event = DROPPED_EVENT_ID,
	135	.x1 = num_available,
	136	};
	137	unused = fwrite(&record, sizeof(record), 1, trace_fp);
	138	writeout_idx += num_available;
	139	}
26f7227b	140
0b5538c3 SH	141	idx = writeout_idx % TRACE_BUF_LEN;
	142	while (get_trace_record(idx, &record)) {
	143	trace_buf[idx].event = 0; /* clear valid bit */
	144	unused = fwrite(&record, sizeof(record), 1, trace_fp);
	145	idx = ++writeout_idx % TRACE_BUF_LEN;
	146	}
26f7227b	147
0b5538c3	148	fflush(trace_fp);
26f7227b	149	}
0b5538c3	150	return NULL;
26f7227b SH	151	}
	152
	153	static void trace(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3,
	154	uint64_t x4, uint64_t x5, uint64_t x6)
	155	{
0b5538c3 SH	156	unsigned int idx;
0b5538c3 SH	157	uint64_t timestamp;
26f7227b	158
22890ab5 PS	159	if (!trace_list[event].state) {
	160	return;
	161	}
	162
0b5538c3 SH	163	timestamp = get_clock();
0b5538c3 SH	164
85aff158	165	idx = g_atomic_int_exchange_and_add((gint *)&trace_idx, 1) % TRACE_BUF_LEN;
0b5538c3 SH	166	trace_buf[idx] = (TraceRecord){
	167	.event = event,
	168	.timestamp_ns = timestamp,
	169	.x1 = x1,
	170	.x2 = x2,
	171	.x3 = x3,
	172	.x4 = x4,
	173	.x5 = x5,
	174	.x6 = x6,
	175	};
	176	__sync_synchronize(); /* write barrier before marking as valid */
	177	trace_buf[idx].event \|= TRACE_RECORD_VALID;
	178
	179	if ((idx + 1) % TRACE_BUF_FLUSH_THRESHOLD == 0) {
	180	flush_trace_file(false);
26f7227b SH	181	}
	182	}
	183
	184	void trace0(TraceEventID event)
	185	{
	186	trace(event, 0, 0, 0, 0, 0, 0);
	187	}
	188
	189	void trace1(TraceEventID event, uint64_t x1)
	190	{
	191	trace(event, x1, 0, 0, 0, 0, 0);
	192	}
	193
	194	void trace2(TraceEventID event, uint64_t x1, uint64_t x2)
	195	{
	196	trace(event, x1, x2, 0, 0, 0, 0);
	197	}
	198
	199	void trace3(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3)
	200	{
	201	trace(event, x1, x2, x3, 0, 0, 0);
	202	}
	203
	204	void trace4(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4)
	205	{
	206	trace(event, x1, x2, x3, x4, 0, 0);
	207	}
	208
	209	void trace5(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5)
	210	{
	211	trace(event, x1, x2, x3, x4, x5, 0);
	212	}
	213
	214	void trace6(TraceEventID event, uint64_t x1, uint64_t x2, uint64_t x3, uint64_t x4, uint64_t x5, uint64_t x6)
	215	{
	216	trace(event, x1, x2, x3, x4, x5, x6);
	217	}
	218
0b5538c3 SH	219	void st_set_trace_file_enabled(bool enable)
	220	{
	221	if (enable == !!trace_fp) {
	222	return; /* no change */
	223	}
	224
	225	/* Halt trace writeout */
	226	flush_trace_file(true);
	227	trace_writeout_enabled = false;
	228	flush_trace_file(true);
	229
	230	if (enable) {
	231	static const TraceRecord header = {
	232	.event = HEADER_EVENT_ID,
	233	.timestamp_ns = HEADER_MAGIC,
	234	.x1 = HEADER_VERSION,
	235	};
	236
6c2a4074	237	trace_fp = fopen(trace_file_name, "wb");
0b5538c3 SH	238	if (!trace_fp) {
	239	return;
	240	}
	241
	242	if (fwrite(&header, sizeof header, 1, trace_fp) != 1) {
	243	fclose(trace_fp);
	244	trace_fp = NULL;
	245	return;
	246	}
	247
	248	/* Resume trace writeout */
	249	trace_writeout_enabled = true;
	250	flush_trace_file(false);
	251	} else {
	252	fclose(trace_fp);
	253	trace_fp = NULL;
	254	}
	255	}
	256
26f7227b	257	/**
0b5538c3 SH	258	* Set the name of a trace file
	259	*
	260	* @file The trace file name or NULL for the default name-<pid> set at
	261	* config time
26f7227b	262	*/
0b5538c3	263	bool st_set_trace_file(const char *file)
26f7227b	264	{
0b5538c3 SH	265	st_set_trace_file_enabled(false);
	266
	267	free(trace_file_name);
	268
	269	if (!file) {
	270	if (asprintf(&trace_file_name, CONFIG_TRACE_FILE, getpid()) < 0) {
	271	trace_file_name = NULL;
	272	return false;
	273	}
	274	} else {
	275	if (asprintf(&trace_file_name, "%s", file) < 0) {
	276	trace_file_name = NULL;
	277	return false;
	278	}
	279	}
	280
	281	st_set_trace_file_enabled(true);
	282	return true;
	283	}
	284
	285	void st_print_trace_file_status(FILE stream, int (stream_printf)(FILE stream, const char fmt, ...))
	286	{
	287	stream_printf(stream, "Trace file \"%s\" %s.\n",
	288	trace_file_name, trace_fp ? "on" : "off");
26f7227b	289	}
22890ab5 PS	290
	291	void st_print_trace(FILE stream, int (stream_printf)(FILE stream, const char fmt, ...))
	292	{
	293	unsigned int i;
	294
0b5538c3 SH	295	for (i = 0; i < TRACE_BUF_LEN; i++) {
	296	TraceRecord record;
	297
	298	if (!get_trace_record(i, &record)) {
	299	continue;
	300	}
a12c668f BS	301	stream_printf(stream, "Event %" PRIu64 " : %" PRIx64 " %" PRIx64
a12c668f BS	302	" %" PRIx64 " %" PRIx64 " %" PRIx64 " %" PRIx64 "\n",
0b5538c3 SH	303	record.event, record.x1, record.x2,
	304	record.x3, record.x4, record.x5,
	305	record.x6);
22890ab5 PS	306	}
	307	}
	308
fc764105 L	309	void st_flush_trace_buffer(void)
	310	{
	311	flush_trace_file(true);
	312	}
	313
	314	void trace_print_events(FILE *stream, fprintf_function stream_printf)
22890ab5 PS	315	{
	316	unsigned int i;
	317
	318	for (i = 0; i < NR_TRACE_EVENTS; i++) {
	319	stream_printf(stream, "%s [Event ID %u] : state %u\n",
	320	trace_list[i].tp_name, i, trace_list[i].state);
	321	}
	322	}
	323
fc764105	324	bool trace_event_set_state(const char *name, bool state)
22890ab5 PS	325	{
22890ab5 PS	326	unsigned int i;
454e202d MW	327	unsigned int len;
	328	bool wildcard = false;
	329	bool matched = false;
	330
	331	len = strlen(name);
	332	if (len > 0 && name[len - 1] == '*') {
	333	wildcard = true;
	334	len -= 1;
	335	}
22890ab5	336	for (i = 0; i < NR_TRACE_EVENTS; i++) {
454e202d MW	337	if (wildcard) {
	338	if (!strncmp(trace_list[i].tp_name, name, len)) {
	339	trace_list[i].state = state;
	340	matched = true;
	341	}
	342	continue;
	343	}
0b5538c3	344	if (!strcmp(trace_list[i].tp_name, name)) {
fc764105	345	trace_list[i].state = state;
0b5538c3	346	return true;
22890ab5 PS	347	}
22890ab5 PS	348	}
454e202d	349	return matched;
0b5538c3 SH	350	}
0b5538c3 SH	351
85aff158 SH	352	/* Helper function to create a thread with signals blocked. Use glib's
	353	* portable threads since QEMU abstractions cannot be used due to reentrancy in
	354	* the tracer. Also note the signal masking on POSIX hosts so that the thread
	355	* does not steal signals when the rest of the program wants them blocked.
	356	*/
	357	static GThread *trace_thread_create(GThreadFunc fn)
22890ab5	358	{
85aff158 SH	359	GThread *thread;
85aff158 SH	360	#ifndef _WIN32
0b5538c3	361	sigset_t set, oldset;
22890ab5	362
0b5538c3 SH	363	sigfillset(&set);
0b5538c3 SH	364	pthread_sigmask(SIG_SETMASK, &set, &oldset);
85aff158 SH	365	#endif
	366	thread = g_thread_create(writeout_thread, NULL, FALSE, NULL);
	367	#ifndef _WIN32
0b5538c3	368	pthread_sigmask(SIG_SETMASK, &oldset, NULL);
85aff158	369	#endif
0b5538c3	370
85aff158 SH	371	return thread;
	372	}
	373
	374	bool trace_backend_init(const char events, const char file)
	375	{
	376	GThread *thread;
	377
	378	if (!g_thread_supported()) {
42ed3727	379	#if !GLIB_CHECK_VERSION(2, 31, 0)
85aff158	380	g_thread_init(NULL);
42ed3727 AL	381	#else
	382	fprintf(stderr, "glib threading failed to initialize.\n");
	383	exit(1);
	384	#endif
85aff158 SH	385	}
	386
	387	trace_available_cond = g_cond_new();
	388	trace_empty_cond = g_cond_new();
	389
	390	thread = trace_thread_create(writeout_thread);
	391	if (!thread) {
e4858974	392	fprintf(stderr, "warning: unable to initialize simple trace backend\n");
85aff158	393	return false;
22890ab5	394	}
0b5538c3	395
85aff158 SH	396	atexit(st_flush_trace_buffer);
	397	trace_backend_init_events(events);
	398	st_set_trace_file(file);
31d3c9b8	399	return true;
22890ab5	400	}