On 4/8/21 7:25 AM, Michał Mirosław wrote:
On Thu, Apr 08, 2021 at 06:13:44AM +0200, Michał Mirosław wrote:
On Fri, Apr 02, 2021 at 07:02:32PM +0300, Dmitry Osipenko wrote:
02.04.2021 00:19, Michał Mirosław пишет:
On Fri, Mar 26, 2021 at 04:34:13PM +0200, Mikko Perttunen wrote:
On 3/23/21 12:16 PM, Thierry Reding wrote:
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@xxxxxxxxxx>
---
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?
Considering this is just a debug facility, I think I prefer not adding a new
field just for it.
This looks like IRQ-disabled region, so unless only root can trigger
this code, maybe the additional field could save a potential headache?
How many waiters can there be in the worst case?
The host1x's IRQ handler runs in a workqueue, so it should be okay.
Why, then, this uses a spinlock (and it has 'intr' in its name)?
The critical sections are already O(n) in number of waiters, so this
patch doesn't make things worse as I previously thought. The questions
remain: What is the expected number and upper bound of workers?
Shouldn't this be a mutex instead?
Everything is primarily for historical reasons. The name 'intr' is
because this is in the part of the host1x driver that handles syncpoint
threshold interrupts - just some of it is in interrupt context and some not.
In any case, this code is scheduled for a complete redesign once we get
the UAPI changes done. I'll take this into account at that point.
Cheers,
Mikko
Best Regards
Michał Mirosław
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