Re: [PATCH v2 05/10] coresight: trbe: Drop duplicate TRUNCATE flags

[Suzuki K Poulose]

On 30/07/2021 05:47, Anshuman Khandual wrote:
> On 7/23/21 6:16 PM, Suzuki K Poulose wrote:
> > We mark the buffer as TRUNCATED when there is no space left
> > in the buffer. But we do it at different points.
> >      __trbe_normal_offset()
> > and also, at all the callers of the above function via
> > compute_trbe_buffer_limit(), when the limit == base (i.e
> > offset = 0 as returned by the __trbe_normal_offset()).
> >
> > So, given that the callers already mark the buffer as TRUNCATED
> > drop the caller inside the __trbe_normal_offset().
> >
> > This is in preparation to moving the handling of TRUNCATED
> > into a central place.
> >
> > Cc: Anshuman Khandual <anshuman.khandual@xxxxxxx>
> > Cc: Mathieu Poirier <mathieu.poirier@xxxxxxxxxx>
> > Cc: Mike Leach <mike.leach@xxxxxxxxxx>
> > Cc: Leo Yan <leo.yan@xxxxxxxxxx>
> > Signed-off-by: Suzuki K Poulose <suzuki.poulose@xxxxxxx>
> > ---
> >   drivers/hwtracing/coresight/coresight-trbe.c | 7 +------
> >   1 file changed, 1 insertion(+), 6 deletions(-)
> >
> > diff --git a/drivers/hwtracing/coresight/coresight-trbe.c b/drivers/hwtracing/coresight/coresight-trbe.c
> > index 446f080f8320..62e1a08f73ff 100644
> > --- a/drivers/hwtracing/coresight/coresight-trbe.c
> > +++ b/drivers/hwtracing/coresight/coresight-trbe.c
> > @@ -253,13 +253,9 @@ static unsigned long __trbe_normal_offset(struct perf_output_handle *handle)
> >   	 * trbe_base				trbe_base + nr_pages
> >   	 *
> >   	 * Perf aux buffer does not have any space for the driver to write into.
> > -	 * Just communicate trace truncation event to the user space by marking
> > -	 * it with PERF_AUX_FLAG_TRUNCATED.
> >   	 */
> > -	if (!handle->size) {
> > -		perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
> > +	if (!handle->size)
> >   		return 0;
> > -	}
> >   
> >   	/* Compute the tail and wakeup indices now that we've aligned head */
> >   	tail = PERF_IDX2OFF(handle->head + handle->size, buf);
> > @@ -361,7 +357,6 @@ static unsigned long __trbe_normal_offset(struct perf_output_handle *handle)
> >   		return limit;
> >   
> >   	trbe_pad_buf(handle, handle->size);
> > -	perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
> >   	return 0;
> >   }
>
> What about in trbe_handle_spurious() path which used to set the flag via
> compute_trbe_buffer_limit(), but would not any more after this change. I
> guess following additional change would be required to preserve the past
> behaviour.
>
> --- a/drivers/hwtracing/coresight/coresight-trbe.c
> +++ b/drivers/hwtracing/coresight/coresight-trbe.c
> @@ -685,6 +685,7 @@ static void trbe_handle_spurious(struct perf_output_handle *handle)
>          buf->trbe_write = buf->trbe_base + PERF_IDX2OFF(handle->head, buf);
>          if (buf->trbe_limit == buf->trbe_base) {
>                  trbe_drain_and_disable_local();
> +               perf_aux_output_flag(handle, PERF_AUX_FLAG_TRUNCATED);
>                  return;
>          }
>          trbe_enable_hw(buf);

Agreed, I will add this.

Thanks
Suzuki