On Sat, 2012-05-26 at 06:39 -0700, Anton Vorontsov wrote:
> If tracer->init() fails, current code will leave current_tracer pointing
> to an unusable tracer, which at best makes 'current_tracer' report
> inaccurate value.
>
> Fix the issue by pointing current_tracer to nop tracer, and only update
> current_tracer with the new one after all the initialization succeeds.
>
Hmm, I'll look at this in more detail. This may be something I pull now.
(for 3.6).
-- Steve
> Signed-off-by: Anton Vorontsov <anton.vorontsov@xxxxxxxxxx>
> ---
> kernel/trace/trace.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c
> index 68032c6..5cf7e67 100644
> --- a/kernel/trace/trace.c
> +++ b/kernel/trace/trace.c
> @@ -3172,10 +3172,10 @@ static int tracing_set_tracer(const char *buf)
> }
> destroy_trace_option_files(topts);
>
> - current_trace = t;
> + current_trace = &nop_trace;
>
> - topts = create_trace_option_files(current_trace);
> - if (current_trace->use_max_tr) {
> + topts = create_trace_option_files(t);
> + if (t->use_max_tr) {
> int cpu;
> /* we need to make per cpu buffer sizes equivalent */
> for_each_tracing_cpu(cpu) {
> @@ -3195,6 +3195,7 @@ static int tracing_set_tracer(const char *buf)
> goto out;
> }
>
> + current_trace = t;
> trace_branch_enable(tr);
> out:
> mutex_unlock(&trace_types_lock);
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