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SubjectRe: [PATCH 1/3] tracing/ftrace: don't insert TRACE_PRINT during selftests
2008/12/4 Steven Rostedt <rostedt@goodmis.org>:
> The comment style should be:
>
> /*
> * comment
> * comment
> * comment
> */

Sorry, will fix it.

>
>> +static atomic_t tracing_selftest_running = ATOMIC_INIT(0);
>
> Do we need that is atomic? Also, it needs to be __read_mostly.


I thought it should be atomic to be sure the value is synchronized
on smp when read. But actually that should have been more likely an
int with smp_wb after writing it.

>> +
>> /* For tracers that don't implement custom flags */
>> static struct tracer_opt dummy_tracer_opt[] = {
>> { }
>> @@ -589,6 +597,8 @@ int register_tracer(struct tracer *type)
>> struct tracer *saved_tracer = current_trace;
>> struct trace_array *tr = &global_trace;
>> int i;
>> +
>> + atomic_set(&tracing_selftest_running, 1);
>
> Enable this in the mutex lock, and we could make it a normal int.
>


But ftrace_printk can be called from interrupt context. I think we can loose
some TRACE_PRINT entries at the selftests time since the tracer are not enabled
by the user at this time, except the boot tracer...

>> /*
>> * Run a selftest on this tracer.
>> * Here we reset the trace buffer, and set the current
>> @@ -603,6 +613,7 @@ int register_tracer(struct tracer *type)
>> /* the test is responsible for initializing and enabling */
>> pr_info("Testing tracer %s: ", type->name);
>> ret = type->selftest(type, tr);
>> + atomic_set(&tracing_selftest_running, 0);
>> /* the test is responsible for resetting too */
>> current_trace = saved_tracer;
>> if (ret) {
>> @@ -3594,7 +3605,7 @@ int trace_vprintk(unsigned long ip, int depth, const char *fmt, va_list args)
>> unsigned long flags, irq_flags;
>> int cpu, len = 0, size, pc;
>>
>> - if (tracing_disabled)
>> + if (tracing_disabled || atomic_read(&tracing_selftest_running))
>> return 0;
>>
>> pc = preempt_count();
>> --
>
> -- Steve
>
>


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