On Mon, Jan 11, 2021 at 03:00:01PM +0200, Mikko Perttunen wrote:
> Show the number of pending waiters in the debugfs status file.
> This is useful for testing to verify that waiters do not leak
> or accumulate incorrectly.
> 
> Signed-off-by: Mikko Perttunen <mperttunen@nvidia.com>
> ---
>  drivers/gpu/host1x/debug.c | 14 +++++++++++---
>  1 file changed, 11 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/gpu/host1x/debug.c b/drivers/gpu/host1x/debug.c
> index 1b4997bda1c7..8a14880c61bb 100644
> --- a/drivers/gpu/host1x/debug.c
> +++ b/drivers/gpu/host1x/debug.c
> @@ -69,6 +69,7 @@ static int show_channel(struct host1x_channel *ch, void *data, bool show_fifo)
>  
>  static void show_syncpts(struct host1x *m, struct output *o)
>  {
> +	struct list_head *pos;
>  	unsigned int i;
>  
>  	host1x_debug_output(o, "---- syncpts ----\n");
> @@ -76,12 +77,19 @@ static void show_syncpts(struct host1x *m, struct output *o)
>  	for (i = 0; i < host1x_syncpt_nb_pts(m); i++) {
>  		u32 max = host1x_syncpt_read_max(m->syncpt + i);
>  		u32 min = host1x_syncpt_load(m->syncpt + i);
> +		unsigned int waiters = 0;
>  
> -		if (!min && !max)
> +		spin_lock(&m->syncpt[i].intr.lock);
> +		list_for_each(pos, &m->syncpt[i].intr.wait_head)
> +			waiters++;
> +		spin_unlock(&m->syncpt[i].intr.lock);

Would it make sense to keep a running count so that we don't have to
compute it here?

> +
> +		if (!min && !max && !waiters)
>  			continue;
>  
> -		host1x_debug_output(o, "id %u (%s) min %d max %d\n",
> -				    i, m->syncpt[i].name, min, max);
> +		host1x_debug_output(o,
> +				    "id %u (%s) min %d max %d (%d waiters)\n",
> +				    i, m->syncpt[i].name, min, max, waiters);

Or alternatively, would it be useful to collect a bit more information
about waiters so that when they leak we get a better understanding of
which ones leak?

It doesn't look like we currently have much information in struct
host1x_waitlist to identify waiters, but perhaps that can be extended?

Thierry