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Subject[PATCH 2/6] tracing: event_id_read() uses simple buffer instead of trace_seq

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

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c
index 04d3f90..835b370 100644
--- a/kernel/trace/trace_events.c
+++ b/kernel/trace/trace_events.c
@@ -604,23 +604,16 @@ static ssize_t
event_id_read(struct file *filp, char __user *ubuf, size_t cnt, loff_t *ppos)
{
struct ftrace_event_call *call = filp->private_data;
- struct trace_seq *s;
- int r;
+ char buf[20];
+ int len;

if (*ppos)
return 0;

- s = kmalloc(sizeof(*s), GFP_KERNEL);
- if (!s)
- return -ENOMEM;
+ len = snprintf(buf, sizeof(buf), "%d\n", call->id);
+ len = simple_read_from_buffer(ubuf, cnt, ppos, buf, len);

- trace_seq_init(s);
- trace_seq_printf(s, "%d\n", call->id);
-
- r = simple_read_from_buffer(ubuf, cnt, ppos,
- s->buffer, s->len);
- kfree(s);
- return r;
+ return len;
}

static ssize_t



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