Re: [PATCH v5 03/21] gpu: host1x: Show number of pending waiters in debugfs

Thierry Reding
2021-03-23T10:16:38Z

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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

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