On 3/29/21 11:27 PM, Dmitry Osipenko wrote:
29.03.2021 16:38, Mikko Perttunen пишет:
Before this patch, cancelled waiters would only be cleaned up
once their threshold value was reached. Make host1x_intr_put_ref
process the cancellation immediately to fix this.
Signed-off-by: Mikko Perttunen <mperttunen@xxxxxxxxxx>
---
v6:
* Call schedule instead of cpu_relax while waiting for pending
interrupt processing
v5:
* Add parameter to flush, i.e. wait for all pending waiters to
complete before returning. The reason this is not always true
is that the pending waiter might be the place that is calling
the put_ref.
---
drivers/gpu/host1x/intr.c | 23 +++++++++++++++++------
drivers/gpu/host1x/intr.h | 4 +++-
drivers/gpu/host1x/syncpt.c | 2 +-
3 files changed, 21 insertions(+), 8 deletions(-)
diff --git a/drivers/gpu/host1x/intr.c b/drivers/gpu/host1x/intr.c
index 9245add23b5d..69b0e8e41466 100644
--- a/drivers/gpu/host1x/intr.c
+++ b/drivers/gpu/host1x/intr.c
@@ -242,18 +242,29 @@ int host1x_intr_add_action(struct host1x *host, struct host1x_syncpt *syncpt,
return 0;
}
-void host1x_intr_put_ref(struct host1x *host, unsigned int id, void *ref)
+void host1x_intr_put_ref(struct host1x *host, unsigned int id, void *ref,
+ bool flush)
{
struct host1x_waitlist *waiter = ref;
struct host1x_syncpt *syncpt;
- while (atomic_cmpxchg(&waiter->state, WLS_PENDING, WLS_CANCELLED) ==
- WLS_REMOVED)
- schedule();
+ atomic_cmpxchg(&waiter->state, WLS_PENDING, WLS_CANCELLED);
syncpt = host->syncpt + id;
- (void)process_wait_list(host, syncpt,
- host1x_syncpt_load(host->syncpt + id));
+
+ spin_lock(&syncpt->intr.lock);
+ if (atomic_cmpxchg(&waiter->state, WLS_CANCELLED, WLS_HANDLED) ==
+ WLS_CANCELLED) {
+ list_del(&waiter->list);
+ kref_put(&waiter->refcount, waiter_release);
+ }
+ spin_unlock(&syncpt->intr.lock);
Looks like we need to use IRQ-safe version of the locking here in order
not to race with the interrupt handler(?), preventing lockup.
The potential contention is with the syncpt_thresh_work scheduled work,
and not the actual interrupt handler, so there is no issue.
But what real bug is fixed by this patch? If no real problem is fixed,
then maybe will be better to defer touching this code till we will just
replace it all with a proper dma-fence handlers?
It improves things in that we won't litter the waiter data structures
with unbounded waiter entries when waits are cancelled. Also, I prefer
working in steps when possible - next is writing dma_fences on top of
this (which is already done) and then eventually phasing/refactoring
code from intr.c to fence.c so eventually only dma_fences remain. In my
experience that works better than big rewrites.
Mikko
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