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tracing: tracing_stats_read() uses simple buffer instead of trace_seq

PATCH In review Lai Jiangshan 2 participants 2 messages Jan 19, 2010 – Jan 20, 2010 Tracing

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Lai Jiangshan

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#0 lore raw

PATCH 3/6 tracing: tracing_stats_read() uses simple buffer instead of trace_seq

It seems that struct trace_seq is too heavy for tracing_stats_read(). we use simple buffer instead of struct trace_seq.

Signed-off-by Lai Jiangshan <[email protected]>

---

kernel/trace/trace.c +7 -12
index 27fecf8..aa1cd92 100644
@@ -3807,27 +3807,22 @@ tracing_stats_read(struct file *filp, char __user *ubuf,
 {
 	unsigned long cpu = (unsigned long)filp->private_data;
 	struct trace_array *tr = &global_trace;
-	struct trace_seq *s;
 	unsigned long cnt;
 
-	s = kmalloc(sizeof(*s), GFP_KERNEL);
-	if (!s)
-		return -ENOMEM;
-
-	trace_seq_init(s);
+	unsigned char buf[128];
+	int len = 0;
 
 	cnt = ring_buffer_entries_cpu(tr->buffer, cpu);
-	trace_seq_printf(s, "entries: %ld\n", cnt);
+	len += sprintf(buf + len, "entries: %ld\n", cnt);
 
 	cnt = ring_buffer_overrun_cpu(tr->buffer, cpu);
-	trace_seq_printf(s, "overrun: %ld\n", cnt);
+	len += sprintf(buf + len, "overrun: %ld\n", cnt);
 
 	cnt = ring_buffer_commit_overrun_cpu(tr->buffer, cpu);
-	trace_seq_printf(s, "commit overrun: %ld\n", cnt);
-
-	count = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->len);
+	len += sprintf(buf + len, "commit overrun: %ld\n", cnt);
 
-	kfree(s);
+	BUG_ON(len >= sizeof(buf)); /* should not happen, 128 is enough. */
+	count = simple_read_from_buffer(ubuf, count, ppos, buf, len);
 
 	return count;
 }
#1 lore raw
Quoted 13 lines · Lai Jiangshan

It seems that struct trace_seq is too heavy for tracing_stats_read(). we use simple buffer instead of struct trace_seq.

Signed-off-by Lai Jiangshan <[email protected]>

---

kernel/trace/trace.c +0 -0
index 27fecf8..aa1cd92 100644
@@ -3807,27 +3807,22 @@ tracing_stats_read(struct file *filp, char __user *ubuf,
 {
 	unsigned long cpu = (unsigned long)filp->private_data;

kernel/trace/trace.c tracing_stats_read(struct file *filp, char __user *ubuf, · line 3812

Quoted 10 lines
kernel/trace/trace.c +1 -6
 	struct trace_array *tr = &global_trace;
-	struct trace_seq *s;
 	unsigned long cnt;
 
-	s = kmalloc(sizeof(*s), GFP_KERNEL);
-	if (!s)
-		return -ENOMEM;
-
-	trace_seq_init(s);
+	unsigned char buf[128];

No problem with the conversion. But perhaps keep using a dynamic buffer as 128 is a bit big for a kernel stack.

Quoted 23 lines
kernel/trace/trace.c +6 -6
+	int len = 0;
 
 	cnt = ring_buffer_entries_cpu(tr->buffer, cpu);
-	trace_seq_printf(s, "entries: %ld\n", cnt);
+	len += sprintf(buf + len, "entries: %ld\n", cnt);
 
 	cnt = ring_buffer_overrun_cpu(tr->buffer, cpu);
-	trace_seq_printf(s, "overrun: %ld\n", cnt);
+	len += sprintf(buf + len, "overrun: %ld\n", cnt);
 
 	cnt = ring_buffer_commit_overrun_cpu(tr->buffer, cpu);
-	trace_seq_printf(s, "commit overrun: %ld\n", cnt);
-
-	count = simple_read_from_buffer(ubuf, count, ppos, s->buffer, s->len);
+	len += sprintf(buf + len, "commit overrun: %ld\n", cnt);
 
-	kfree(s);
+	BUG_ON(len >= sizeof(buf)); /* should not happen, 128 is enough. */
+	count = simple_read_from_buffer(ubuf, count, ppos, buf, len);
 
 	return count;
 }