2022-05-09 05:58:40

by Jiapeng Chong

Subject: [PATCH] perf cs-etm: Use swap() instead of open coding it

Clean the following coccicheck warning:

./tools/perf/util/cs-etm.c:418:34-35: WARNING opportunity for swap().

Reported-by: Abaci Robot <[email protected]>
Signed-off-by: Jiapeng Chong <[email protected]>
---
tools/perf/util/cs-etm.c | 9 ++-------
1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
index 8b95fb3c4d7b..0cb555cc766f 100644
--- a/tools/perf/util/cs-etm.c
+++ b/tools/perf/util/cs-etm.c
@@ -406,18 +406,13 @@ struct cs_etm_packet_queue
static void cs_etm__packet_swap(struct cs_etm_auxtrace *etm,
struct cs_etm_traceid_queue *tidq)
{
- struct cs_etm_packet *tmp;
-
if (etm->synth_opts.branches || etm->synth_opts.last_branch ||
- etm->synth_opts.instructions) {
+ etm->synth_opts.instructions)
/*
* Swap PACKET with PREV_PACKET: PACKET becomes PREV_PACKET for
* the next incoming packet.
*/
- tmp = tidq->packet;
- tidq->packet = tidq->prev_packet;
- tidq->prev_packet = tmp;
- }
+ swap(tidq->packet, tidq->prev_packet);
}

static void cs_etm__packet_dump(const char *pkt_string)
--
2.20.1.7.g153144c

2022-06-20 17:40:56

by Mathieu Poirier

Subject: Re: [PATCH] perf cs-etm: Use swap() instead of open coding it

[Adding James]

Hi Jiapeng,

On Fri, May 06, 2022 at 05:17:18PM +0800, Jiapeng Chong wrote:
> Clean the following coccicheck warning:
>
> ./tools/perf/util/cs-etm.c:418:34-35: WARNING opportunity for swap().
>
> Reported-by: Abaci Robot <[email protected]>
> Signed-off-by: Jiapeng Chong <[email protected]>
> ---
> tools/perf/util/cs-etm.c | 9 ++-------
> 1 file changed, 2 insertions(+), 7 deletions(-)
>
> diff --git a/tools/perf/util/cs-etm.c b/tools/perf/util/cs-etm.c
> index 8b95fb3c4d7b..0cb555cc766f 100644
> --- a/tools/perf/util/cs-etm.c
> +++ b/tools/perf/util/cs-etm.c
> @@ -406,18 +406,13 @@ struct cs_etm_packet_queue
> static void cs_etm__packet_swap(struct cs_etm_auxtrace *etm,
> struct cs_etm_traceid_queue *tidq)
> {
> - struct cs_etm_packet *tmp;
> -
> if (etm->synth_opts.branches || etm->synth_opts.last_branch ||
> - etm->synth_opts.instructions) {
> + etm->synth_opts.instructions)
> /*
> * Swap PACKET with PREV_PACKET: PACKET becomes PREV_PACKET for
> * the next incoming packet.
> */
> - tmp = tidq->packet;
> - tidq->packet = tidq->prev_packet;
> - tidq->prev_packet = tmp;

Those 3 lines have burned a lot of eyes... As far as I can remember the idea is
simply to make sure that after that point, ->prev_packet is now set to ->packet
in preparation for the next iteration. There is no point in setting ->packet to
->prev_packet. As such the following would work just fine:

tidq->prev_packet = tidq->packet;

... but I will let James and Leo have a final say on that.

> - }
> + swap(tidq->packet, tidq->prev_packet);

If we absolutely need to keep swapping the packets please add the header file
where swap() is found.

Thanks,
Mathieu

> }
>
> static void cs_etm__packet_dump(const char *pkt_string)
> --
> 2.20.1.7.g153144c
>