linux-kernel - Re: [PATCH v2] dynamic debug: allow printing to trace event

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Date:   Fri, 14 Aug 2020 13:15:31 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Vincent Whitchurch <vincent.whitchurch@...s.com>
Cc:     <jbaron@...mai.com>, <mingo@...hat.com>, <kernel@...s.com>,
        <corbet@....net>, <pmladek@...e.com>,
        <sergey.senozhatsky@...il.com>, <john.ogness@...utronix.de>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] dynamic debug: allow printing to trace event

On Fri, 14 Aug 2020 15:31:51 +0200
Vincent Whitchurch <vincent.whitchurch@...s.com> wrote:
> index aa9ff9e1c0b3..f599ed21ecc5 100644
> --- a/include/linux/dynamic_debug.h
> +++ b/include/linux/dynamic_debug.h
> @@ -27,13 +27,16 @@ struct _ddebug {
>  	 * writes commands to <debugfs>/dynamic_debug/control
>  	 */
>  #define _DPRINTK_FLAGS_NONE	0
> -#define _DPRINTK_FLAGS_PRINT	(1<<0) /* printk() a message using the format */
> +#define _DPRINTK_FLAGS_PRINTK	(1<<0) /* printk() a message using the format */

The above looks like a cleanup unrelated to this patch, and probably
should be on its own.

>  #define _DPRINTK_FLAGS_INCL_MODNAME	(1<<1)
>  #define _DPRINTK_FLAGS_INCL_FUNCNAME	(1<<2)
>  #define _DPRINTK_FLAGS_INCL_LINENO	(1<<3)
>  #define _DPRINTK_FLAGS_INCL_TID		(1<<4)
> +#define _DPRINTK_FLAGS_TRACE		(1<<5)	
> +#define _DPRINTK_FLAGS_PRINT		(_DPRINTK_FLAGS_PRINTK | \
> +					 _DPRINTK_FLAGS_TRACE)
>  #if defined DEBUG
> -#define _DPRINTK_FLAGS_DEFAULT _DPRINTK_FLAGS_PRINT
> +#define _DPRINTK_FLAGS_DEFAULT _DPRINTK_FLAGS_PRINTK
>  #else
>  #define _DPRINTK_FLAGS_DEFAULT 0
>  #endif
> diff --git a/include/trace/events/printk.h b/include/trace/events/printk.h
> index 13d405b2fd8b..6c89121a1669 100644
> --- a/include/trace/events/printk.h
> +++ b/include/trace/events/printk.h
> @@ -7,7 +7,7 @@
>  
>  #include <linux/tracepoint.h>
>  
> -TRACE_EVENT(console,
> +DECLARE_EVENT_CLASS(printk,
>  	TP_PROTO(const char *text, size_t len),
>  
>  	TP_ARGS(text, len),
> @@ -31,6 +31,16 @@ TRACE_EVENT(console,
>  
>  	TP_printk("%s", __get_str(msg))
>  );
> +
> +DEFINE_EVENT(printk, console,
> +	TP_PROTO(const char *text, size_t len),
> +	TP_ARGS(text, len)
> +);
> +
> +DEFINE_EVENT(printk, dynamic,

Can we call this "dynamic_printk" or "printk_dynamic", as
trace_dynamic() is too generic.

> +	TP_PROTO(const char *text, size_t len),
> +	TP_ARGS(text, len)
> +);
>  #endif /* _TRACE_PRINTK_H */
>  
>  /* This part must be outside protection */
> diff --git a/lib/dynamic_debug.c b/lib/dynamic_debug.c
> index 1d012e597cc3..76fc3e33fe41 100644
> --- a/lib/dynamic_debug.c
> +++ b/lib/dynamic_debug.c
> @@ -36,6 +36,7 @@
>  #include <linux/sched.h>
>  #include <linux/device.h>
>  #include <linux/netdevice.h>
> +#include <trace/events/printk.h>
>  
>  #include <rdma/ib_verbs.h>
>  
> @@ -84,11 +85,12 @@ static inline const char *trim_prefix(const char *path)
>  }
>  
>  static struct { unsigned flag:8; char opt_char; } opt_array[] = {
> -	{ _DPRINTK_FLAGS_PRINT, 'p' },
> +	{ _DPRINTK_FLAGS_PRINTK, 'p' },

Again, this looks unrelated, and shouldn't be part of this patch.

>  	{ _DPRINTK_FLAGS_INCL_MODNAME, 'm' },
>  	{ _DPRINTK_FLAGS_INCL_FUNCNAME, 'f' },
>  	{ _DPRINTK_FLAGS_INCL_LINENO, 'l' },
>  	{ _DPRINTK_FLAGS_INCL_TID, 't' },
> +	{ _DPRINTK_FLAGS_TRACE, 'x' },
>  	{ _DPRINTK_FLAGS_NONE, '_' },
>  };
>  

Other then the two comments above, I'm fine with this change.

Reviewed-by: Steven Rostedt (VMware) <rostedt@...dmis.org>

-- Steve