2021-07-23 15:43:09

by Christophe JAILLET

Subject: [PATCH] HID: logitech-hidpp: Use 'atomic_inc_return' instead of hand-writing it

This function logs a warning if the workqueue gets too big.
In order to save a few cycles, use 'atomic_inc_return()' instead of an
'atomic_inc()/atomic_read()' sequence.

This axes a line of code and saves a 'atomic_read()' call.

Signed-off-by: Christophe JAILLET <[email protected]>
---
drivers/hid/hid-logitech-hidpp.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
index 61635e629469..a7fa35245c2e 100644
--- a/drivers/hid/hid-logitech-hidpp.c
+++ b/drivers/hid/hid-logitech-hidpp.c
@@ -2240,11 +2240,10 @@ static int hidpp_ff_queue_work(struct hidpp_ff_private_data *data, int effect_id
wd->size = size;
memcpy(wd->params, params, size);

- atomic_inc(&data->workqueue_size);
+ s = atomic_inc_return(&data->workqueue_size);
queue_work(data->wq, &wd->work);

/* warn about excessive queue size */
- s = atomic_read(&data->workqueue_size);
if (s >= 20 && s % 20 == 0)
hid_warn(data->hidpp->hid_dev, "Force feedback command queue contains %d commands, causing substantial delays!", s);

--
2.30.2

2021-08-20 12:24:39

by Jiri Kosina

Subject: Re: [PATCH] HID: logitech-hidpp: Use 'atomic_inc_return' instead of hand-writing it

On Fri, 23 Jul 2021, Christophe JAILLET wrote:

> This function logs a warning if the workqueue gets too big.
> In order to save a few cycles, use 'atomic_inc_return()' instead of an
> 'atomic_inc()/atomic_read()' sequence.
>
> This axes a line of code and saves a 'atomic_read()' call.
>
> Signed-off-by: Christophe JAILLET <[email protected]>
> ---
> drivers/hid/hid-logitech-hidpp.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/drivers/hid/hid-logitech-hidpp.c b/drivers/hid/hid-logitech-hidpp.c
> index 61635e629469..a7fa35245c2e 100644
> --- a/drivers/hid/hid-logitech-hidpp.c
> +++ b/drivers/hid/hid-logitech-hidpp.c
> @@ -2240,11 +2240,10 @@ static int hidpp_ff_queue_work(struct hidpp_ff_private_data *data, int effect_id
> wd->size = size;
> memcpy(wd->params, params, size);
>
> - atomic_inc(&data->workqueue_size);
> + s = atomic_inc_return(&data->workqueue_size);
> queue_work(data->wq, &wd->work);
>
> /* warn about excessive queue size */
> - s = atomic_read(&data->workqueue_size);
> if (s >= 20 && s % 20 == 0)
> hid_warn(data->hidpp->hid_dev, "Force feedback command queue contains %d commands, causing substantial delays!", s);

Applied, thank you.

--
Jiri Kosina
SUSE Labs