Re: [for-next][PATCH 13/23] USB: mtu3: tracing: Use the new __vstring() helper

[Steven Rostedt]

On Fri, 15 Jul 2022 18:01:44 +0800
Chunfeng Yun <chunfeng.yun@xxxxxxxxxxxx> wrote:

>  irq/254-1120100-137     [000] d..1.   266.629662: mtu3_log:
> 11201000.usb: ep0_state SETUPr-speed
> 
> "r-speed" seems the remain of last log;

I found an off-by-one bug in the vstring patch. I'll rebase, test and try
again.

In the mean time, care to add this on top to make sure it's fixed?

Thanks!

-- Steve

diff --git a/include/linux/trace_events.h b/include/linux/trace_events.h
index e6f8ba52a958..b18759a673c6 100644
--- a/include/linux/trace_events.h
+++ b/include/linux/trace_events.h
@@ -922,16 +922,16 @@ perf_trace_buf_submit(void *raw_data, int size, int rctx, u16 type,
  * gcc warns that you can not use a va_list in an inlined
  * function. But lets me make it into a macro :-/
  */
-#define __trace_event_vstr_len(fmt, va)		\
-({						\
-	va_list __ap;				\
-	int __ret;				\
-						\
-	va_copy(__ap, *(va));			\
-	__ret = vsnprintf(NULL, 0, fmt, __ap);	\
-	va_end(__ap);				\
-						\
-	min(__ret, TRACE_EVENT_STR_MAX);	\
+#define __trace_event_vstr_len(fmt, va)			\
+({							\
+	va_list __ap;					\
+	int __ret;					\
+							\
+	va_copy(__ap, *(va));				\
+	__ret = vsnprintf(NULL, 0, fmt, __ap) + 1;	\
+	va_end(__ap);					\
+							\
+	min(__ret, TRACE_EVENT_STR_MAX);		\
 })
 
 #endif /* _LINUX_TRACE_EVENT_H */