linux-kernel - Re: [PATCH V7 02/14] rtla: Helper functions for rtla

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Date:   Thu, 25 Nov 2021 14:42:17 +0100
From:   Daniel Bristot de Oliveira <bristot@...nel.org>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     Tao Zhou <tao.zhou@...ux.dev>, Ingo Molnar <mingo@...hat.com>,
        Tom Zanussi <zanussi@...nel.org>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Clark Williams <williams@...hat.com>,
        John Kacur <jkacur@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        linux-rt-users@...r.kernel.org, linux-trace-devel@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH V7 02/14] rtla: Helper functions for rtla

On 11/24/21 22:37, Steven Rostedt wrote:
> On Fri, 29 Oct 2021 21:26:05 +0200
> Daniel Bristot de Oliveira <bristot@...nel.org> wrote:
> 
>> +/*
>> + * enable_tracer_by_name - enable a tracer on the given instance
>> + */
>> +int enable_tracer_by_name(struct tracefs_instance *inst, const char *tracer)
>> +{
>> +	enum tracefs_tracers t;
>> +	int retval;
>> +
>> +	t = TRACEFS_TRACER_CUSTOM;
>> +
>> +	debug_msg("enabling %s tracer\n", tracer);
>> +
>> +	retval = tracefs_tracer_set(inst, t, tracer);
> 
> Interesting. We had discussions about having the custom option (which I
> fought for, for this very reason).
> 
>> +	if (retval < 0) {
>> +		if (errno == ENODEV)
>> +			err_msg("tracer %s not found!\n", tracer);
>> +
>> +		err_msg("failed to enable the tracer %s\n", tracer);
>> +		return -1;
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>> +/*
>> + * disable_tracer - set nop tracer to the insta
>> + */
>> +void disable_tracer(struct tracefs_instance *inst)
>> +{
>> +	enum tracefs_tracers t = TRACEFS_TRACER_NOP;
>> +	int retval;
>> +
>> +	retval = tracefs_tracer_set(inst, t);
>> +	if (retval < 0)
>> +		err_msg("oops, error disabling tracer\n");
>> +}
>> +
>> +/*
>> + * create_instance - create a trace instance with *instance_name
>> + */
>> +struct tracefs_instance *create_instance(char *instance_name)
>> +{
>> +	return tracefs_instance_create(instance_name);
>> +}
>> +
>> +/*
>> + * destroy_instance - remove a trace instance and free the data
>> + */
>> +void destroy_instance(struct tracefs_instance *inst)
>> +{
>> +	tracefs_instance_destroy(inst);
>> +	tracefs_instance_free(inst);
>> +}
>> +
>> +/*
>> + * save_trace_to_file - save the trace output of the instance to the file
>> + */
>> +int save_trace_to_file(struct tracefs_instance *inst, const char *filename)
>> +{
>> +	const char *file = "trace";
>> +	mode_t mode = 0644;
>> +	char *buffer[4096];
> 
> Did you really mean to have buffer be 4096 strings?
> 
> Or did you mean:
> 
> 	char buffer[4096];

I should be "char buffer[4096];" I will fix that.

(The * is probably a left over from the idea of using a malloc(4096)...)

-- Daniel


> (i.e. a single string of 4096 size)?
> 
> -- Steve
>