Merge tag 'perf-core-for-mingo-20160429' of git://git.kernel.org/pub/scm/linux/kernel/git/acme/linux into perf/core

Pull perf/core improvements and fixes from Arnaldo Carvalho de Melo:

User visible changes:

- Allow generate timestamped suffixed multiple perf.data files upon receiving
SIGUSR2 in 'perf record', to slice a long running monitoring session, allowing
to dump uninteresting sessions (Wang Nan)

- Handle ENOMEM for perf_event_max_stack + PERF_SAMPLE_CALLCHAIN
in perf_evsel__open_strerror(), showing a more informative
message when the request call stack depth can't be allocated by
the kernel (Arnaldo Carvalho de Melo)

Infrastructure changes:

- Use strbuf for making strings in 'perf probe' (Masami Hiramatsu)

- Do not use sizeof on pointer type, not a problem since its a pointer to
pointer, fix none the less. Found by Coccinelle (Vaishali Thakkar)

Cleanups:

- Fix for Coverity found issues in the bpf feature build test (Florian Fainelli)

Signed-off-by: Arnaldo Carvalho de Melo <[e-mail]>
Signed-off-by: Ingo Molnar <[e-mail]>

tools/build/feature/test-bpf.c

···
 	attr.log_level = 0;
 	attr.kern_version = 0;
 
-	attr = attr;
 	/*
 	 * Test existence of __NR_bpf and BPF_PROG_LOAD.
 	 * This call should fail if we run the testcase.
 	 */
-	return syscall(__NR_bpf, BPF_PROG_LOAD, attr, sizeof(attr));
+	return syscall(__NR_bpf, BPF_PROG_LOAD, &attr, sizeof(attr));
 }

tools/perf/Documentation/perf-record.txt

···
 --all-user::
 Configure all used events to run in user space.
 
+--timestamp-filename
+Append timestamp to output file name.
+
+--switch-output::
+Generate multiple perf.data files, timestamp prefixed, switching to a new one
+when receiving a SIGUSR2.
+
+A possible use case is to, given an external event, slice the perf.data file
+that gets then processed, possibly via a perf script, to decide if that
+particular perf.data snapshot should be kept or not.
+
+Implies --timestamp-filename, --no-buildid and --no-buildid-cache.
+
 SEE ALSO
 --------
 linkperf:perf-stat[1], linkperf:perf-list[1]

tools/perf/builtin-record.c

···
 #include "util/parse-regs-options.h"
 #include "util/llvm-utils.h"
 #include "util/bpf-loader.h"
+#include "util/trigger.h"
 #include "asm/bug.h"
 
 #include <unistd.h>
···
 	bool			no_buildid_cache_set;
 	bool			buildid_all;
 	bool			timestamp_filename;
+	bool			switch_output;
 	unsigned long long	samples;
 };
 
···
 static volatile int signr = -1;
 static volatile int child_finished;
 
-static volatile enum {
-	AUXTRACE_SNAPSHOT_OFF = -1,
-	AUXTRACE_SNAPSHOT_DISABLED = 0,
-	AUXTRACE_SNAPSHOT_ENABLED = 1,
-} auxtrace_snapshot_state = AUXTRACE_SNAPSHOT_OFF;
-
-static inline void
-auxtrace_snapshot_on(void)
-{
-	auxtrace_snapshot_state = AUXTRACE_SNAPSHOT_DISABLED;
-}
-
-static inline void
-auxtrace_snapshot_enable(void)
-{
-	if (auxtrace_snapshot_state == AUXTRACE_SNAPSHOT_OFF)
-		return;
-	auxtrace_snapshot_state = AUXTRACE_SNAPSHOT_ENABLED;
-}
-
-static inline void
-auxtrace_snapshot_disable(void)
-{
-	if (auxtrace_snapshot_state == AUXTRACE_SNAPSHOT_OFF)
-		return;
-	auxtrace_snapshot_state = AUXTRACE_SNAPSHOT_DISABLED;
-}
-
-static inline bool
-auxtrace_snapshot_is_enabled(void)
-{
-	if (auxtrace_snapshot_state == AUXTRACE_SNAPSHOT_OFF)
-		return false;
-	return auxtrace_snapshot_state == AUXTRACE_SNAPSHOT_ENABLED;
-}
-
-static volatile int auxtrace_snapshot_err;
 static volatile int auxtrace_record__snapshot_started;
+static DEFINE_TRIGGER(auxtrace_snapshot_trigger);
+static DEFINE_TRIGGER(switch_output_trigger);
 
 static void sig_handler(int sig)
 {
···
 {
 	pr_debug("Recording AUX area tracing snapshot\n");
 	if (record__auxtrace_read_snapshot_all(rec) < 0) {
-		auxtrace_snapshot_err = -1;
+		trigger_error(&auxtrace_snapshot_trigger);
 	} else {
-		auxtrace_snapshot_err = auxtrace_record__snapshot_finish(rec->itr);
-		if (!auxtrace_snapshot_err)
-			auxtrace_snapshot_enable();
+		if (auxtrace_record__snapshot_finish(rec->itr))
+			trigger_error(&auxtrace_snapshot_trigger);
+		else
+			trigger_ready(&auxtrace_snapshot_trigger);
 	}
 }
 
···
 	return;
 }
 
+static int record__synthesize_workload(struct record *rec)
+{
+	struct {
+		struct thread_map map;
+		struct thread_map_data map_data;
+	} thread_map;
+
+	thread_map.map.nr = 1;
+	thread_map.map.map[0].pid = rec->evlist->workload.pid;
+	thread_map.map.map[0].comm = NULL;
+	return perf_event__synthesize_thread_map(&rec->tool, &thread_map.map,
+						 process_synthesized_event,
+						 &rec->session->machines.host,
+						 rec->opts.sample_address,
+						 rec->opts.proc_map_timeout);
+}
+
+static int record__synthesize(struct record *rec);
+
 static int
 record__switch_output(struct record *rec, bool at_exit)
 {
···
 	if (!quiet)
 		fprintf(stderr, "[ perf record: Dump %s.%s ]\n",
 			file->path, timestamp);
+
+	/* Output tracking events */
+	if (!at_exit) {
+		record__synthesize(rec);
+
+		/*
+		 * In 'perf record --switch-output' without -a,
+		 * record__synthesize() in record__switch_output() won't
+		 * generate tracking events because there's no thread_map
+		 * in evlist. Which causes newly created perf.data doesn't
+		 * contain map and comm information.
+		 * Create a fake thread_map and directly call
+		 * perf_event__synthesize_thread_map() for those events.
+		 */
+		if (target__none(&rec->opts.target))
+			record__synthesize_workload(rec);
+	}
 	return fd;
 }
 
···
 	signal(SIGINT, sig_handler);
 	signal(SIGTERM, sig_handler);
 
-	if (rec->opts.auxtrace_snapshot_mode) {
+	if (rec->opts.auxtrace_snapshot_mode || rec->switch_output) {
 		signal(SIGUSR2, snapshot_sig_handler);
-		auxtrace_snapshot_on();
+		if (rec->opts.auxtrace_snapshot_mode)
+			trigger_on(&auxtrace_snapshot_trigger);
+		if (rec->switch_output)
+			trigger_on(&switch_output_trigger);
 	} else {
 		signal(SIGUSR2, SIG_IGN);
 	}
···
 		perf_evlist__enable(rec->evlist);
 	}
 
-	auxtrace_snapshot_enable();
+	trigger_ready(&auxtrace_snapshot_trigger);
+	trigger_ready(&switch_output_trigger);
 	for (;;) {
 		unsigned long long hits = rec->samples;
 
 		if (record__mmap_read_all(rec) < 0) {
-			auxtrace_snapshot_disable();
+			trigger_error(&auxtrace_snapshot_trigger);
+			trigger_error(&switch_output_trigger);
 			err = -1;
 			goto out_child;
 		}
 
 		if (auxtrace_record__snapshot_started) {
 			auxtrace_record__snapshot_started = 0;
-			if (!auxtrace_snapshot_err)
+			if (!trigger_is_error(&auxtrace_snapshot_trigger))
 				record__read_auxtrace_snapshot(rec);
-			if (auxtrace_snapshot_err) {
+			if (trigger_is_error(&auxtrace_snapshot_trigger)) {
 				pr_err("AUX area tracing snapshot failed\n");
 				err = -1;
+				goto out_child;
+			}
+		}
+
+		if (trigger_is_hit(&switch_output_trigger)) {
+			trigger_ready(&switch_output_trigger);
+
+			if (!quiet)
+				fprintf(stderr, "[ perf record: dump data: Woken up %ld times ]\n",
+					waking);
+			waking = 0;
+			fd = record__switch_output(rec, false);
+			if (fd < 0) {
+				pr_err("Failed to switch to new file\n");
+				trigger_error(&switch_output_trigger);
+				err = fd;
 				goto out_child;
 			}
 		}
···
 		 * disable events in this case.
 		 */
 		if (done && !disabled && !target__none(&opts->target)) {
-			auxtrace_snapshot_disable();
+			trigger_off(&auxtrace_snapshot_trigger);
 			perf_evlist__disable(rec->evlist);
 			disabled = true;
 		}
 	}
-	auxtrace_snapshot_disable();
+	trigger_off(&auxtrace_snapshot_trigger);
+	trigger_off(&switch_output_trigger);
 
 	if (forks && workload_exec_errno) {
 		char msg[STRERR_BUFSIZE];
···
 		    "Record build-id of all DSOs regardless of hits"),
 	OPT_BOOLEAN(0, "timestamp-filename", &record.timestamp_filename,
 		    "append timestamp to output filename"),
+	OPT_BOOLEAN(0, "switch-output", &record.switch_output,
+		    "Switch output when receive SIGUSR2"),
 	OPT_END()
 };
 
···
 		return -EINVAL;
 	}
 
+	if (rec->switch_output)
+		rec->timestamp_filename = true;
+
 	if (!rec->itr) {
 		rec->itr = auxtrace_record__init(rec->evlist, &err);
 		if (err)
···
 "If some relocation was applied (e.g. kexec) symbols may be misresolved\n"
 "even with a suitable vmlinux or kallsyms file.\n\n");
 
-	if (rec->no_buildid_cache || rec->no_buildid)
+	if (rec->no_buildid_cache || rec->no_buildid) {
 		disable_buildid_cache();
+	} else if (rec->switch_output) {
+		/*
+		 * In 'perf record --switch-output', disable buildid
+		 * generation by default to reduce data file switching
+		 * overhead. Still generate buildid if they are required
+		 * explicitly using
+		 *
+		 *  perf record --signal-trigger --no-no-buildid \
+		 *              --no-no-buildid-cache
+		 *
+		 * Following code equals to:
+		 *
+		 * if ((rec->no_buildid || !rec->no_buildid_set) &&
+		 *     (rec->no_buildid_cache || !rec->no_buildid_cache_set))
+		 *         disable_buildid_cache();
+		 */
+		bool disable = true;
+
+		if (rec->no_buildid_set && !rec->no_buildid)
+			disable = false;
+		if (rec->no_buildid_cache_set && !rec->no_buildid_cache)
+			disable = false;
+		if (disable) {
+			rec->no_buildid = true;
+			rec->no_buildid_cache = true;
+			disable_buildid_cache();
+		}
+	}
 
 	if (rec->evlist->nr_entries == 0 &&
 	    perf_evlist__add_default(rec->evlist) < 0) {
···
 
 static void snapshot_sig_handler(int sig __maybe_unused)
 {
-	if (!auxtrace_snapshot_is_enabled())
-		return;
-	auxtrace_snapshot_disable();
-	auxtrace_snapshot_err = auxtrace_record__snapshot_start(record.itr);
-	auxtrace_record__snapshot_started = 1;
+	if (trigger_is_ready(&auxtrace_snapshot_trigger)) {
+		trigger_hit(&auxtrace_snapshot_trigger);
+		auxtrace_record__snapshot_started = 1;
+		if (auxtrace_record__snapshot_start(record.itr))
+			trigger_error(&auxtrace_snapshot_trigger);
+	}
+
+	if (trigger_is_ready(&switch_output_trigger))
+		trigger_hit(&switch_output_trigger);
 }

tools/perf/builtin-trace.c

···
 # define O_CLOEXEC		02000000
 #endif
 
-#ifndef MSG_CMSG_CLOEXEC
-# define MSG_CMSG_CLOEXEC	0x40000000
-#endif
-
 struct trace {
 	struct perf_tool	tool;
 	struct syscalltbl	*sctbl;
···
 };
 static DEFINE_STRARRAY(socket_families);
 
-#ifndef MSG_PROBE
-#define MSG_PROBE	     0x10
-#endif
-#ifndef MSG_WAITFORONE
-#define MSG_WAITFORONE	0x10000
-#endif
-#ifndef MSG_SENDPAGE_NOTLAST
-#define MSG_SENDPAGE_NOTLAST 0x20000
-#endif
-#ifndef MSG_FASTOPEN
-#define MSG_FASTOPEN	     0x20000000
-#endif
-
-static size_t syscall_arg__scnprintf_msg_flags(char *bf, size_t size,
-					       struct syscall_arg *arg)
-{
-	int printed = 0, flags = arg->val;
-
-	if (flags == 0)
-		return scnprintf(bf, size, "NONE");
-#define	P_MSG_FLAG(n) \
-	if (flags & MSG_##n) { \
-		printed += scnprintf(bf + printed, size - printed, "%s%s", printed ? "|" : "", #n); \
-		flags &= ~MSG_##n; \
-	}
-
-	P_MSG_FLAG(OOB);
-	P_MSG_FLAG(PEEK);
-	P_MSG_FLAG(DONTROUTE);
-	P_MSG_FLAG(TRYHARD);
-	P_MSG_FLAG(CTRUNC);
-	P_MSG_FLAG(PROBE);
-	P_MSG_FLAG(TRUNC);
-	P_MSG_FLAG(DONTWAIT);
-	P_MSG_FLAG(EOR);
-	P_MSG_FLAG(WAITALL);
-	P_MSG_FLAG(FIN);
-	P_MSG_FLAG(SYN);
-	P_MSG_FLAG(CONFIRM);
-	P_MSG_FLAG(RST);
-	P_MSG_FLAG(ERRQUEUE);
-	P_MSG_FLAG(NOSIGNAL);
-	P_MSG_FLAG(MORE);
-	P_MSG_FLAG(WAITFORONE);
-	P_MSG_FLAG(SENDPAGE_NOTLAST);
-	P_MSG_FLAG(FASTOPEN);
-	P_MSG_FLAG(CMSG_CLOEXEC);
-#undef P_MSG_FLAG
-
-	if (flags)
-		printed += scnprintf(bf + printed, size - printed, "%s%#x", printed ? "|" : "", flags);
-
-	return printed;
-}
-
-#define SCA_MSG_FLAGS syscall_arg__scnprintf_msg_flags
-
 static size_t syscall_arg__scnprintf_access_mode(char *bf, size_t size,
 						 struct syscall_arg *arg)
 {
···
 #include "trace/beauty/pid.c"
 #include "trace/beauty/mmap.c"
 #include "trace/beauty/mode_t.c"
+#include "trace/beauty/msg_flags.c"
 #include "trace/beauty/perf_event_open.c"
 #include "trace/beauty/sched_policy.c"
 #include "trace/beauty/socket_type.c"

tools/perf/tests/dso-data.c

···
 {
 	int i;
 
-	dsos = malloc(sizeof(dsos) * cnt);
+	dsos = malloc(sizeof(*dsos) * cnt);
 	TEST_ASSERT_VAL("failed to alloc dsos array", dsos);
 
 	for (i = 0; i < cnt; i++) {

tools/perf/trace/beauty/msg_flags.c

···
+#include <sys/types.h>
+#include <sys/socket.h>
+
+#ifndef MSG_PROBE
+#define MSG_PROBE		     0x10
+#endif
+#ifndef MSG_WAITFORONE
+#define MSG_WAITFORONE		   0x10000
+#endif
+#ifndef MSG_SENDPAGE_NOTLAST
+#define MSG_SENDPAGE_NOTLAST	   0x20000
+#endif
+#ifndef MSG_FASTOPEN
+#define MSG_FASTOPEN		0x20000000
+#endif
+#ifndef MSG_CMSG_CLOEXEC
+# define MSG_CMSG_CLOEXEC	0x40000000
+#endif
+
+static size_t syscall_arg__scnprintf_msg_flags(char *bf, size_t size,
+					       struct syscall_arg *arg)
+{
+	int printed = 0, flags = arg->val;
+
+	if (flags == 0)
+		return scnprintf(bf, size, "NONE");
+#define	P_MSG_FLAG(n) \
+	if (flags & MSG_##n) { \
+		printed += scnprintf(bf + printed, size - printed, "%s%s", printed ? "|" : "", #n); \
+		flags &= ~MSG_##n; \
+	}
+
+	P_MSG_FLAG(OOB);
+	P_MSG_FLAG(PEEK);
+	P_MSG_FLAG(DONTROUTE);
+	P_MSG_FLAG(TRYHARD);
+	P_MSG_FLAG(CTRUNC);
+	P_MSG_FLAG(PROBE);
+	P_MSG_FLAG(TRUNC);
+	P_MSG_FLAG(DONTWAIT);
+	P_MSG_FLAG(EOR);
+	P_MSG_FLAG(WAITALL);
+	P_MSG_FLAG(FIN);
+	P_MSG_FLAG(SYN);
+	P_MSG_FLAG(CONFIRM);
+	P_MSG_FLAG(RST);
+	P_MSG_FLAG(ERRQUEUE);
+	P_MSG_FLAG(NOSIGNAL);
+	P_MSG_FLAG(MORE);
+	P_MSG_FLAG(WAITFORONE);
+	P_MSG_FLAG(SENDPAGE_NOTLAST);
+	P_MSG_FLAG(FASTOPEN);
+	P_MSG_FLAG(CMSG_CLOEXEC);
+#undef P_MSG_FLAG
+
+	if (flags)
+		printed += scnprintf(bf + printed, size - printed, "%s%#x", printed ? "|" : "", flags);
+
+	return printed;
+}
+
+#define SCA_MSG_FLAGS syscall_arg__scnprintf_msg_flags

tools/perf/util/evsel.c

···
 			 "Probably the maximum number of open file descriptors has been reached.\n"
 			 "Hint: Try again after reducing the number of events.\n"
 			 "Hint: Try increasing the limit with 'ulimit -n <limit>'");
+	case ENOMEM:
+		if ((evsel->attr.sample_type & PERF_SAMPLE_CALLCHAIN) != 0 &&
+		    access("/proc/sys/kernel/perf_event_max_stack", F_OK) == 0)
+			return scnprintf(msg, size,
+					 "Not enough memory to setup event with callchain.\n"
+					 "Hint: Try tweaking /proc/sys/kernel/perf_event_max_stack\n"
+					 "Hint: Current value: %d", sysctl_perf_event_max_stack);
+		break;
 	case ENODEV:
 		if (target->cpu_list)
 			return scnprintf(msg, size, "%s",
-	 "No such device - did you specify an out-of-range profile CPU?\n");
+	 "No such device - did you specify an out-of-range profile CPU?");
 		break;
 	case EOPNOTSUPP:
 		if (evsel->attr.precise_ip)
···
 	return scnprintf(msg, size,
 	"The sys_perf_event_open() syscall returned with %d (%s) for event (%s).\n"
 	"/bin/dmesg may provide additional information.\n"
-	"No CONFIG_PERF_EVENTS=y kernel support configured?\n",
+	"No CONFIG_PERF_EVENTS=y kernel support configured?",
 			 err, strerror_r(err, sbuf, sizeof(sbuf)),
 			 perf_evsel__name(evsel));
 }

tools/perf/util/probe-event.c

···
 }
 
 /* Compose only probe arg */
-int synthesize_perf_probe_arg(struct perf_probe_arg *pa, char *buf, size_t len)
+char *synthesize_perf_probe_arg(struct perf_probe_arg *pa)
 {
 	struct perf_probe_arg_field *field = pa->field;
-	int ret;
-	char *tmp = buf;
+	struct strbuf buf;
+	char *ret;
 
+	strbuf_init(&buf, 64);
 	if (pa->name && pa->var)
-		ret = e_snprintf(tmp, len, "%s=%s", pa->name, pa->var);
+		strbuf_addf(&buf, "%s=%s", pa->name, pa->var);
 	else
-		ret = e_snprintf(tmp, len, "%s", pa->name ? pa->name : pa->var);
-	if (ret <= 0)
-		goto error;
-	tmp += ret;
-	len -= ret;
+		strbuf_addstr(&buf, pa->name ?: pa->var);
 
 	while (field) {
 		if (field->name[0] == '[')
-			ret = e_snprintf(tmp, len, "%s", field->name);
+			strbuf_addstr(&buf, field->name);
 		else
-			ret = e_snprintf(tmp, len, "%s%s",
-					 field->ref ? "->" : ".", field->name);
-		if (ret <= 0)
-			goto error;
-		tmp += ret;
-		len -= ret;
+			strbuf_addf(&buf, "%s%s", field->ref ? "->" : ".",
+				    field->name);
 		field = field->next;
 	}
 
-	if (pa->type) {
-		ret = e_snprintf(tmp, len, ":%s", pa->type);
-		if (ret <= 0)
-			goto error;
-		tmp += ret;
-		len -= ret;
-	}
+	if (pa->type)
+		strbuf_addf(&buf, ":%s", pa->type);
 
-	return tmp - buf;
-error:
-	pr_debug("Failed to synthesize perf probe argument: %d\n", ret);
+	ret = strbuf_detach(&buf, NULL);
+
 	return ret;
 }
 
 /* Compose only probe point (not argument) */
 static char *synthesize_perf_probe_point(struct perf_probe_point *pp)
 {
-	char *buf, *tmp;
-	char offs[32] = "", line[32] = "", file[32] = "";
-	int ret, len;
+	struct strbuf buf;
+	char *tmp;
+	int len;
 
-	buf = zalloc(MAX_CMDLEN);
-	if (buf == NULL) {
-		ret = -ENOMEM;
-		goto error;
-	}
-	if (pp->offset) {
-		ret = e_snprintf(offs, 32, "+%lu", pp->offset);
-		if (ret <= 0)
-			goto error;
-	}
-	if (pp->line) {
-		ret = e_snprintf(line, 32, ":%d", pp->line);
-		if (ret <= 0)
-			goto error;
+	strbuf_init(&buf, 64);
+	if (pp->function) {
+		strbuf_addstr(&buf, pp->function);
+		if (pp->offset)
+			strbuf_addf(&buf, "+%lu", pp->offset);
+		else if (pp->line)
+			strbuf_addf(&buf, ":%d", pp->line);
+		else if (pp->retprobe)
+			strbuf_addstr(&buf, "%return");
 	}
 	if (pp->file) {
 		tmp = pp->file;
···
 			tmp = strchr(pp->file + len - 30, '/');
 			tmp = tmp ? tmp + 1 : pp->file + len - 30;
 		}
-		ret = e_snprintf(file, 32, "@%s", tmp);
-		if (ret <= 0)
-			goto error;
+		strbuf_addf(&buf, "@%s", tmp);
+		if (!pp->function && pp->line)
+			strbuf_addf(&buf, ":%d", pp->line);
 	}
 
-	if (pp->function)
-		ret = e_snprintf(buf, MAX_CMDLEN, "%s%s%s%s%s", pp->function,
-				 offs, pp->retprobe ? "%return" : "", line,
-				 file);
-	else
-		ret = e_snprintf(buf, MAX_CMDLEN, "%s%s", file, line);
-	if (ret <= 0)
-		goto error;
-
-	return buf;
-error:
-	pr_debug("Failed to synthesize perf probe point: %d\n", ret);
-	free(buf);
-	return NULL;
+	return strbuf_detach(&buf, NULL);
 }
 
 #if 0
···
 #endif
 
 static int __synthesize_probe_trace_arg_ref(struct probe_trace_arg_ref *ref,
-					     char **buf, size_t *buflen,
-					     int depth)
+					    struct strbuf *buf, int depth)
 {
-	int ret;
 	if (ref->next) {
 		depth = __synthesize_probe_trace_arg_ref(ref->next, buf,
-							 buflen, depth + 1);
+							 depth + 1);
 		if (depth < 0)
 			goto out;
 	}
-
-	ret = e_snprintf(*buf, *buflen, "%+ld(", ref->offset);
-	if (ret < 0)
-		depth = ret;
-	else {
-		*buf += ret;
-		*buflen -= ret;
-	}
+	strbuf_addf(buf, "%+ld(", ref->offset);
 out:
 	return depth;
-
 }
 
 static int synthesize_probe_trace_arg(struct probe_trace_arg *arg,
-				       char *buf, size_t buflen)
+				      struct strbuf *buf)
 {
 	struct probe_trace_arg_ref *ref = arg->ref;
-	int ret, depth = 0;
-	char *tmp = buf;
+	int depth = 0;
 
 	/* Argument name or separator */
 	if (arg->name)
-		ret = e_snprintf(buf, buflen, " %s=", arg->name);
+		strbuf_addf(buf, " %s=", arg->name);
 	else
-		ret = e_snprintf(buf, buflen, " ");
-	if (ret < 0)
-		return ret;
-	buf += ret;
-	buflen -= ret;
+		strbuf_addch(buf, ' ');
 
 	/* Special case: @XXX */
 	if (arg->value[0] == '@' && arg->ref)
···
 
 	/* Dereferencing arguments */
 	if (ref) {
-		depth = __synthesize_probe_trace_arg_ref(ref, &buf,
-							  &buflen, 1);
+		depth = __synthesize_probe_trace_arg_ref(ref, buf, 1);
 		if (depth < 0)
 			return depth;
 	}
 
 	/* Print argument value */
 	if (arg->value[0] == '@' && arg->ref)
-		ret = e_snprintf(buf, buflen, "%s%+ld", arg->value,
-				 arg->ref->offset);
+		strbuf_addf(buf, "%s%+ld", arg->value, arg->ref->offset);
 	else
-		ret = e_snprintf(buf, buflen, "%s", arg->value);
-	if (ret < 0)
-		return ret;
-	buf += ret;
-	buflen -= ret;
+		strbuf_addstr(buf, arg->value);
 
 	/* Closing */
-	while (depth--) {
-		ret = e_snprintf(buf, buflen, ")");
-		if (ret < 0)
-			return ret;
-		buf += ret;
-		buflen -= ret;
-	}
+	while (depth--)
+		strbuf_addch(buf, ')');
 	/* Print argument type */
-	if (arg->type) {
-		ret = e_snprintf(buf, buflen, ":%s", arg->type);
-		if (ret <= 0)
-			return ret;
-		buf += ret;
-	}
+	if (arg->type)
+		strbuf_addf(buf, ":%s", arg->type);
 
-	return buf - tmp;
+	return 0;
 }
 
 char *synthesize_probe_trace_command(struct probe_trace_event *tev)
 {
 	struct probe_trace_point *tp = &tev->point;
-	char *buf;
-	int i, len, ret;
-
-	buf = zalloc(MAX_CMDLEN);
-	if (buf == NULL)
-		return NULL;
-
-	len = e_snprintf(buf, MAX_CMDLEN, "%c:%s/%s ", tp->retprobe ? 'r' : 'p',
-			 tev->group, tev->event);
-	if (len <= 0)
-		goto error;
+	struct strbuf buf;
+	char *ret = NULL;
+	int i;
 
 	/* Uprobes must have tp->module */
 	if (tev->uprobes && !tp->module)
-		goto error;
+		return NULL;
+
+	strbuf_init(&buf, 32);
+	strbuf_addf(&buf, "%c:%s/%s ", tp->retprobe ? 'r' : 'p',
+		    tev->group, tev->event);
 	/*
 	 * If tp->address == 0, then this point must be a
 	 * absolute address uprobe.
···
 
 	/* Use the tp->address for uprobes */
 	if (tev->uprobes)
-		ret = e_snprintf(buf + len, MAX_CMDLEN - len, "%s:0x%lx",
-				 tp->module, tp->address);
+		strbuf_addf(&buf, "%s:0x%lx", tp->module, tp->address);
 	else if (!strncmp(tp->symbol, "0x", 2))
 		/* Absolute address. See try_to_find_absolute_address() */
-		ret = e_snprintf(buf + len, MAX_CMDLEN - len, "%s%s0x%lx",
-				 tp->module ?: "", tp->module ? ":" : "",
-				 tp->address);
+		strbuf_addf(&buf, "%s%s0x%lx", tp->module ?: "",
+			    tp->module ? ":" : "", tp->address);
 	else
-		ret = e_snprintf(buf + len, MAX_CMDLEN - len, "%s%s%s+%lu",
-				 tp->module ?: "", tp->module ? ":" : "",
-				 tp->symbol, tp->offset);
+		strbuf_addf(&buf, "%s%s%s+%lu", tp->module ?: "",
+			    tp->module ? ":" : "", tp->symbol, tp->offset);
 
-	if (ret <= 0)
-		goto error;
-	len += ret;
-
-	for (i = 0; i < tev->nargs; i++) {
-		ret = synthesize_probe_trace_arg(&tev->args[i], buf + len,
-						  MAX_CMDLEN - len);
-		if (ret <= 0)
+	for (i = 0; i < tev->nargs; i++)
+		if (synthesize_probe_trace_arg(&tev->args[i], &buf) < 0)
 			goto error;
-		len += ret;
-	}
 
-	return buf;
+	ret = strbuf_detach(&buf, NULL);
 error:
-	free(buf);
-	return NULL;
+	strbuf_release(&buf);
+	return ret;
 }
 
 static int find_perf_probe_point_from_map(struct probe_trace_point *tp,
···
 static int convert_to_perf_probe_event(struct probe_trace_event *tev,
 			       struct perf_probe_event *pev, bool is_kprobe)
 {
-	char buf[64] = "";
+	struct strbuf buf = STRBUF_INIT;
 	int i, ret;
 
 	/* Convert event/group name */
···
 		if (tev->args[i].name)
 			pev->args[i].name = strdup(tev->args[i].name);
 		else {
-			ret = synthesize_probe_trace_arg(&tev->args[i],
-							  buf, 64);
-			pev->args[i].name = strdup(buf);
+			strbuf_init(&buf, 32);
+			ret = synthesize_probe_trace_arg(&tev->args[i], &buf);
+			pev->args[i].name = strbuf_detach(&buf, NULL);
 		}
 		if (pev->args[i].name == NULL && ret >= 0)
 			ret = -ENOMEM;
···
 				     const char *module,
 				     struct strbuf *result)
 {
-	int i, ret;
-	char buf[128];
-	char *place;
+	int i;
+	char *buf;
+
+	if (asprintf(&buf, "%s:%s", group, event) < 0)
+		return -errno;
+	strbuf_addf(result, "  %-20s (on ", buf);
+	free(buf);
 
 	/* Synthesize only event probe point */
-	place = synthesize_perf_probe_point(&pev->point);
-	if (!place)
-		return -EINVAL;
+	buf = synthesize_perf_probe_point(&pev->point);
+	if (!buf)
+		return -ENOMEM;
+	strbuf_addstr(result, buf);
+	free(buf);
 
-	ret = e_snprintf(buf, 128, "%s:%s", group, event);
-	if (ret < 0)
-		goto out;
-
-	strbuf_addf(result, "  %-20s (on %s", buf, place);
 	if (module)
 		strbuf_addf(result, " in %s", module);
 
 	if (pev->nargs > 0) {
 		strbuf_add(result, " with", 5);
 		for (i = 0; i < pev->nargs; i++) {
-			ret = synthesize_perf_probe_arg(&pev->args[i],
-							buf, 128);
-			if (ret < 0)
-				goto out;
+			buf = synthesize_perf_probe_arg(&pev->args[i]);
+			if (!buf)
+				return -ENOMEM;
 			strbuf_addf(result, " %s", buf);
+			free(buf);
 		}
 	}
 	strbuf_addch(result, ')');
-out:
-	free(place);
-	return ret;
+
+	return 0;
 }
 
 /* Show an event */

tools/perf/util/probe-event.h

···
 /* Events to command string */
 char *synthesize_perf_probe_command(struct perf_probe_event *pev);
 char *synthesize_probe_trace_command(struct probe_trace_event *tev);
-int synthesize_perf_probe_arg(struct perf_probe_arg *pa, char *buf, size_t len);
+char *synthesize_perf_probe_arg(struct perf_probe_arg *pa);
 
 /* Check the perf_probe_event needs debuginfo */
 bool perf_probe_event_need_dwarf(struct perf_probe_event *pev);

tools/perf/util/probe-finder.c

···
 static int find_variable(Dwarf_Die *sc_die, struct probe_finder *pf)
 {
 	Dwarf_Die vr_die;
-	char buf[32], *ptr;
+	char *buf, *ptr;
 	int ret = 0;
 
 	/* Copy raw parameters */
···
 	if (pf->pvar->name)
 		pf->tvar->name = strdup(pf->pvar->name);
 	else {
-		ret = synthesize_perf_probe_arg(pf->pvar, buf, 32);
-		if (ret < 0)
-			return ret;
+		buf = synthesize_perf_probe_arg(pf->pvar);
+		if (!buf)
+			return -ENOMEM;
 		ptr = strchr(buf, ':');	/* Change type separator to _ */
 		if (ptr)
 			*ptr = '_';
-		pf->tvar->name = strdup(buf);
+		pf->tvar->name = buf;
 	}
 	if (pf->tvar->name == NULL)
 		return -ENOMEM;
···
 			if (ret2 == 0) {
 				strlist__add(vl->vars,
 					strbuf_detach(&buf, NULL));
-			}
-			strbuf_release(&buf);
+			} else
+				strbuf_release(&buf);
 		}
 	}
 

tools/perf/util/trigger.h

···
+#ifndef __TRIGGER_H_
+#define __TRIGGER_H_ 1
+
+#include "util/debug.h"
+#include "asm/bug.h"
+
+/*
+ * Use trigger to model operations which need to be executed when
+ * an event (a signal, for example) is observed.
+ *
+ * States and transits:
+ *
+ *
+ *  OFF--(on)--> READY --(hit)--> HIT
+ *                 ^               |
+ *                 |            (ready)
+ *                 |               |
+ *                  \_____________/
+ *
+ * is_hit and is_ready are two key functions to query the state of
+ * a trigger. is_hit means the event already happen; is_ready means the
+ * trigger is waiting for the event.
+ */
+
+struct trigger {
+	volatile enum {
+		TRIGGER_ERROR		= -2,
+		TRIGGER_OFF		= -1,
+		TRIGGER_READY		= 0,
+		TRIGGER_HIT		= 1,
+	} state;
+	const char *name;
+};
+
+#define TRIGGER_WARN_ONCE(t, exp) \
+	WARN_ONCE(t->state != exp, "trigger '%s' state transist error: %d in %s()\n", \
+		  t->name, t->state, __func__)
+
+static inline bool trigger_is_available(struct trigger *t)
+{
+	return t->state >= 0;
+}
+
+static inline bool trigger_is_error(struct trigger *t)
+{
+	return t->state <= TRIGGER_ERROR;
+}
+
+static inline void trigger_on(struct trigger *t)
+{
+	TRIGGER_WARN_ONCE(t, TRIGGER_OFF);
+	t->state = TRIGGER_READY;
+}
+
+static inline void trigger_ready(struct trigger *t)
+{
+	if (!trigger_is_available(t))
+		return;
+	t->state = TRIGGER_READY;
+}
+
+static inline void trigger_hit(struct trigger *t)
+{
+	if (!trigger_is_available(t))
+		return;
+	TRIGGER_WARN_ONCE(t, TRIGGER_READY);
+	t->state = TRIGGER_HIT;
+}
+
+static inline void trigger_off(struct trigger *t)
+{
+	if (!trigger_is_available(t))
+		return;
+	t->state = TRIGGER_OFF;
+}
+
+static inline void trigger_error(struct trigger *t)
+{
+	t->state = TRIGGER_ERROR;
+}
+
+static inline bool trigger_is_ready(struct trigger *t)
+{
+	return t->state == TRIGGER_READY;
+}
+
+static inline bool trigger_is_hit(struct trigger *t)
+{
+	return t->state == TRIGGER_HIT;
+}
+
+#define DEFINE_TRIGGER(n) \
+struct trigger n = {.state = TRIGGER_OFF, .name = #n}
+#endif