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SubjectRe: [PATCH v2 2/4] perf ftrace: Add ftrace.tracer config option
Em Tue, Jan 31, 2017 at 09:46:28AM -0300, Arnaldo Carvalho de Melo escreveu:
> Also you are silently ignoring any unknown variable in this section, so
> if someone has this:
>
> cat ~/.perfconfig
>
> [ftrace]
>
> trace = function
>
>
> I.e. forgets the 'r', it will keep using the current default,
> "function_graph" till the user checks the config and adds that missing
> 'r'...
>
> I haven't changed this because I think this is so common that we should
> instead have a different error return for those config callbacks that
> will tell perf_config() to say something like:
>
> "unknown variable %s.%s\n", section_name, variable_name

So I read a bit more the config code and ended up with this:

static int perf_ftrace_config(const char *var, const char *value, void *cb)
{
struct perf_ftrace *ftrace = cb;

if (prefixcmp(var, "ftrace."))
return 0;

if (strcmp(var, "ftrace.tracer"))
return -1;

if (!strcmp(value, "function_graph") ||
!strcmp(value, "function")) {
ftrace->tracer = value;
return 0;
}

pr_err("Please select \"function_graph\" (default) or \"function\"\n");
return -1;
}

I.e. it will ignore variables for other sections and will stop at an unknown
variable or value for ftrace.tracer:

[root@jouet ~]# cat ~/.perfconfig
[ftrace]
trace = function
[root@jouet ~]# perf ftrace usleep 1
Error: wrong config key-value pair ftrace.trace=function
[root@jouet ~]# cat ~/.perfconfig
[ftrace]
tracer = functin
[root@jouet ~]# perf ftrace usleep 1
Please select "function_graph" (default) or "function"
Error: wrong config key-value pair ftrace.tracer=functin
[root@jouet ~]# cat ~/.perfconfig
[ftrace]
tracer = function
[root@jouet ~]# perf ftrace usleep 1 | head -5
<idle>-0 [000] d... 3855.820847: switch_mm_irqs_off <-__schedule
<...>-18550 [000] d... 3855.820849: finish_task_switch <-__schedule
<...>-18550 [000] d... 3855.820851: smp_irq_work_interrupt <-irq_work_interrupt
<...>-18550 [000] d... 3855.820851: irq_enter <-smp_irq_work_interrupt
<...>-18550 [000] d... 3855.820851: rcu_irq_enter <-irq_enter
[root@jouet ~]#

- Arnaldo

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