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SubjectRe: [PATCH v2 2/2] trace: allocate space from temparary trace sequence buffer
On Thu, 15 Dec 2022 12:33:27 +0800
Linyu Yuan <quic_linyyuan@quicinc.com> wrote:

> there is one dwc3 trace event declare as below,
> DECLARE_EVENT_CLASS(dwc3_log_event,
> TP_PROTO(u32 event, struct dwc3 *dwc),
> TP_ARGS(event, dwc),
> TP_STRUCT__entry(
> __field(u32, event)
> __field(u32, ep0state)
> __dynamic_array(char, str, DWC3_MSG_MAX)
> ),
> TP_fast_assign(
> __entry->event = event;
> __entry->ep0state = dwc->ep0state;
> ),
> TP_printk("event (%08x): %s", __entry->event,
> dwc3_decode_event(__get_str(str), DWC3_MSG_MAX,
> __entry->event, __entry->ep0state))
> );
> the problem is when trace function called, it will allocate up to
> DWC3_MSG_MAX bytes from trace event buffer, but never fill the buffer
> during fast assignment, it only fill the buffer when output function are
> called, so this means if output function are not called, the buffer will
> never used.
>
> add __get_buf(len) which allocate space from iter->tmp_seq when trace
> output function called, it allow user write any data to allocatd space.
>
> the mentioned dwc3 trace event will changed as below,
> DECLARE_EVENT_CLASS(dwc3_log_event,
> TP_PROTO(u32 event, struct dwc3 *dwc),
> TP_ARGS(event, dwc),
> TP_STRUCT__entry(
> __field(u32, event)
> __field(u32, ep0state)
> ),
> TP_fast_assign(
> __entry->event = event;
> __entry->ep0state = dwc->ep0state;
> ),
> TP_printk("event (%08x): %s", __entry->event,
> dwc3_decode_event(__get_buf(DWC3_MSG_MAX), DWC3_MSG_MAX,
> __entry->event, __entry->ep0state))
> );.
>
> Signed-off-by: Linyu Yuan <quic_linyyuan@quicinc.com>


No!

Here, I did it for you:

-- Steve

diff --git a/drivers/usb/dwc3/debug.h b/drivers/usb/dwc3/debug.h
index 48b44b88dc25..81abdcbfc660 100644
--- a/drivers/usb/dwc3/debug.h
+++ b/drivers/usb/dwc3/debug.h
@@ -11,6 +11,7 @@
#ifndef __DWC3_DEBUG_H
#define __DWC3_DEBUG_H

+#include <linux/trace_seq.h>
#include "core.h"

/**
@@ -381,6 +382,19 @@ static inline const char *dwc3_decode_event(char *str, size_t size, u32 event,
return dwc3_ep_event_string(str, size, &evt.depevt, ep0state);
}

+static inline const char *dwc3_decode_event_seq(struct trace_seq *p,
+ u32 event, u32 ep0state)
+{
+ char *str = trace_seq_buffer_ptr(p);
+ int size = seq_buf_buffer_left(&p->seq);
+
+ dwc3_decode_event(str, size, event, ep0state);
+
+ seq_buf_commit(&p->seq, strlen(str));
+
+ return str;
+}
+
static inline const char *dwc3_ep_cmd_status_string(int status)
{
switch (status) {
diff --git a/drivers/usb/dwc3/trace.h b/drivers/usb/dwc3/trace.h
index 1975aec8d36d..bee2589e85a8 100644
--- a/drivers/usb/dwc3/trace.h
+++ b/drivers/usb/dwc3/trace.h
@@ -54,15 +54,13 @@ DECLARE_EVENT_CLASS(dwc3_log_event,
TP_STRUCT__entry(
__field(u32, event)
__field(u32, ep0state)
- __dynamic_array(char, str, DWC3_MSG_MAX)
),
TP_fast_assign(
__entry->event = event;
__entry->ep0state = dwc->ep0state;
),
TP_printk("event (%08x): %s", __entry->event,
- dwc3_decode_event(__get_str(str), DWC3_MSG_MAX,
- __entry->event, __entry->ep0state))
+ dwc3_decode_event_seq(p, __entry->event, __entry->ep0state))
);

DEFINE_EVENT(dwc3_log_event, dwc3_event,
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