On 20 October 2015 at 03:56, Alexander Shishkin
<alexander.shishkin@xxxxxxxxxxxxxxx> wrote:
> Mathieu Poirier <mathieu.poirier@xxxxxxxxxx> writes:
>
>> Implementing perf related APIs to activate and terminate
>> a trace session. More specifically dealing with the sink
>> buffer's internal mechanic along with perf's API to start
>> and stop interactions with the ring buffers.
>
> A matter of preference, but I'd say that it would be easier to review
> this part if you merged all the buffer related patches together.
>
>> +static void etb_reset_buffer(struct coresight_device *csdev,
>> + struct perf_output_handle *handle,
>> + void *sink_config)
>> +{
>> + struct cs_buffers *buf = sink_config;
>> + struct etb_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
>> +
>> + if (buf) {
>> + /*
>> + * In snapshot mode ->data_size holds the new address of the
>> + * ring buffer's head. The size itself is the whole address
>> + * range since we want the latest information.
>> + */
>> + if (buf->snapshot)
>> + handle->head = local_xchg(&buf->data_size,
>> + buf->nr_pages << PAGE_SHIFT);
>
> Does it make sense to do this in etb_update_buffer() instead?
I toyed with that idea for a while. I would make sense if the ETB was
generating an interrupt when it is full but since cross-triggers
aren't implemented yet I didn't want to introduce code I can't test.
>
>> + perf_aux_output_end(handle, local_xchg(&buf->data_size, 0),
>> + local_xchg(&buf->lost, 0));
>
> The corresponding perf_aux_output_begin() is done in etm_event_add(),
> I'd suggest that you do this in etm_event_del(),
I'm in total agreement. Since perf_aux_output_begin() is called in
etm_event_add(), perf_aux_output_end() should really be called in
etm_event_del(). The problem is that "buf->data_size" and "buf->lost"
are specific to the sink buffer and shouldn't be made public outside
of it. Let me think about this further.
> unconditionally. Otherwise you're risking ending up with a refcount leak
> and all sorts of horror.
>
> Regards,
> --
> Alex
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