Subject: Re: [PATCH 1/1] tracing: Fix compile error in trace_array calls when TRACING is disabled

From: Steven Rostedt <[email-masked]>
Date: Tue, 6 Sep 2022 22:48:45 -0400

On Tue, 6 Sep 2022 19:38:00 -0700
Arun Easi <[email-masked]> wrote:

> Fix this compilation error seen when CONFIG_TRACING is not enabled:
> 
> drivers/scsi/qla2xxx/qla_os.c: In function 'qla_trace_init':
> drivers/scsi/qla2xxx/qla_os.c:2854:25: error: implicit declaration of function
> 'trace_array_get_by_name'; did you mean 'trace_array_set_clr_event'?
> [-Werror=implicit-function-declaration]
>  2854 |         qla_trc_array = trace_array_get_by_name("qla2xxx");
>       |                         ^~~~~~~~~~~~~~~~~~~~~~~
>       |                         trace_array_set_clr_event
> 
> drivers/scsi/qla2xxx/qla_os.c: In function 'qla_trace_uninit':
> drivers/scsi/qla2xxx/qla_os.c:2869:9: error: implicit declaration of function
> 'trace_array_put' [-Werror=implicit-function-declaration]
>  2869 |         trace_array_put(qla_trc_array);
>       |         ^~~~~~~~~~~~~~~
> 
> Reported-by: kernel test robot <[email-masked]>
> Signed-off-by: Arun Easi <[email-masked]>
> ---
>  include/linux/trace.h | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)
> 
> diff --git a/include/linux/trace.h b/include/linux/trace.h
> index bf16961..bf206c3 100644
> --- a/include/linux/trace.h
> +++ b/include/linux/trace.h
> @@ -48,6 +48,23 @@ void osnoise_arch_unregister(void);
>  void osnoise_trace_irq_entry(int id);
>  void osnoise_trace_irq_exit(int id, const char *desc);
>  
> +#else	/* CONFIG_TRACING */
> +#define TRACE_EXPORT_FUNCTION	0
> +#define TRACE_EXPORT_EVENT	0
> +#define TRACE_EXPORT_MARKER	0
> +struct trace_export { };

The original for the above can just be moved out of the #ifdef
CONFIG_TRACING. No need to "hide" them.

> +#define register_ftrace_export(export) -EINVAL
> +#define unregister_ftrace_export(export) 0
> +#define trace_printk_init_buffers()
> +#define trace_array_printk(tr, ip, fmt, ...) 0
> +#define trace_array_init_printk(tr) -EINVAL
> +#define trace_array_put(tr)
> +#define trace_array_get_by_name(name) NULL
> +#define trace_array_destroy(tr) 0

With the data outside the #ifdef, the above should be converted into static
inlines.

> +#define osnoise_arch_register() -EINVAL
> +#define osnoise_arch_unregister()
> +#define osnoise_trace_irq_entry(id)
> +#define osnoise_trace_irq_exit(id, desc)

No need to define the osnoise functions. These are only here to allow archs
to define them. They should never be referenced when CONFIG_TRACING is not
set.

>  #endif	/* CONFIG_TRACING */
>  
>  #endif	/* _LINUX_TRACE_H */