linux-kernel - [PATCH 1/2] trace-cmd record: refactor set

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Date:   Tue, 22 Nov 2016 15:20:51 -0500
From:   Luiz Capitulino <lcapitulino@...hat.com>
To:     rostedt@...dmis.org
Cc:     linux-kernel@...r.kernel.org
Subject: [PATCH 1/2] trace-cmd record: refactor set_mask()

This commit makes set_mask() more specialized: all
it does now is to write the cpumask to tracing_cpumask.
The handling of "-M -1" is now done by the newly
added alloc_mask_from_hex().

Also, uneeded checks are dropped and
buffer_instance->cpumask points to dynamic memory.

This work is a preparation for supporting the
"--cpu-list" option in the next commit.

Signed-off-by: Luiz Capitulino <lcapitulino@...hat.com>
---
 trace-local.h  |  2 +-
 trace-record.c | 54 ++++++++++++++++++++++++++++++++++--------------------
 2 files changed, 35 insertions(+), 21 deletions(-)

diff --git a/trace-local.h b/trace-local.h
index 62363d0..0ac39bf 100644
--- a/trace-local.h
+++ b/trace-local.h
@@ -143,7 +143,7 @@ struct func_list {
 struct buffer_instance {
 	struct buffer_instance	*next;
 	const char		*name;
-	const char		*cpumask;
+	char			*cpumask;
 	struct event_list	*events;
 	struct event_list	**event_next;
 
diff --git a/trace-record.c b/trace-record.c
index 22b6835..0f1f2c4 100644
--- a/trace-record.c
+++ b/trace-record.c
@@ -69,6 +69,8 @@ enum trace_type {
 	TRACE_TYPE_PROFILE	= (1 << 4) | TRACE_TYPE_STREAM,
 };
 
+#define CPUMASK_STR_MAX 4096 /* Don't expect more than 32768 CPUS */
+
 static int rt_prio;
 
 static int keep;
@@ -2078,27 +2080,24 @@ static void update_pid_event_filters(struct buffer_instance *instance)
 	update_event_filters(instance);
 }
 
-static void set_mask(struct buffer_instance *instance)
-{
-	const char *mask = instance->cpumask;
-	struct stat st;
-	char cpumask[4096]; /* Don't expect more than 32768 CPUS */
-	char *path;
-	int fd;
-	int ret;
 
-	if (!mask)
-		return;
+static char *alloc_mask_from_hex(const char *str)
+{
+	char *cpumask;
 
-	if (strcmp(mask, "-1") == 0) {
+	if (strcmp(str, "-1") == 0) {
 		/* set all CPUs */
 		int bytes = (cpu_count + 7) / 8;
 		int last = cpu_count % 8;
 		int i;
 
-		if (bytes > 4095) {
+		cpumask = malloc(CPUMASK_STR_MAX);
+		if (!cpumask)
+			die("can't allocate cpumask");
+
+		if (bytes > (CPUMASK_STR_MAX-1)) {
 			warning("cpumask can't handle more than 32768 CPUS!");
-			bytes = 4095;
+			bytes = CPUMASK_STR_MAX-1;
 		}
 
 		sprintf(cpumask, "%x", (1 << last) - 1);
@@ -2107,18 +2106,32 @@ static void set_mask(struct buffer_instance *instance)
 			cpumask[i] = 'f';
 
 		cpumask[i+1] = 0;
-
-		mask = cpumask;
+	} else {
+		cpumask = strdup(str);
+		if (!cpumask)
+			die("can't allocate cpumask");
 	}
 
+	return cpumask;
+}
+
+static void set_mask(struct buffer_instance *instance)
+{
+	struct stat st;
+	char *path;
+	int fd;
+	int ret;
+
+	if (!instance->cpumask)
+		return;
+
 	path = get_instance_file(instance, "tracing_cpumask");
 	if (!path)
 		die("could not allocate path");
 
 	ret = stat(path, &st);
 	if (ret < 0) {
-		if (mask)
-			warning("%s not found", path);
+		warning("%s not found", path);
 		goto out;
 	}
 
@@ -2126,12 +2139,13 @@ static void set_mask(struct buffer_instance *instance)
 	if (fd < 0)
 		die("could not open %s\n", path);
 
-	if (mask)
-		write(fd, mask, strlen(mask));
+	write(fd, instance->cpumask, strlen(instance->cpumask));
 	
 	close(fd);
  out:
 	tracecmd_put_tracing_file(path);
+	free(instance->cpumask);
+	instance->cpumask = NULL;
 }
 
 static void enable_events(struct buffer_instance *instance)
@@ -4530,7 +4544,7 @@ void trace_record (int argc, char **argv)
 			max_kb = atoi(optarg);
 			break;
 		case 'M':
-			instance->cpumask = optarg;
+			instance->cpumask = alloc_mask_from_hex(optarg);
 			break;
 		case 't':
 			if (extract)
-- 
2.5.5