habanalabs: fix race condition in multi CS completion

Race condition occurs when CS fence completes and multi CS did not
completed yet, while waiting for multi CS ends and returns indication
to user that the CS completed. Next wait for multi CS may be triggered
by previous multi CS completion without any current CS completed,
causing an error.

Example scenario :
1. User do multi CS wait for CSs 1 and 2 on master QID 0

2. CS 1 and 2 reached the "cs release" code. The thread of CS 1
   completed both the CS and multi CS handling but the completion
   thread of CS 2 completed the CS but still did not executed
   complete_multi_cs (note that in CS completion the sequence is to
   first do complete all for the CS and then another complete all to
   signal the multi_cs)

3. User received indication that CS 1 and 2 completed (since we check
   the CS fence and both indicated as completed) and immediately waits
   on CS 3 and 4, also on master QID 0.

4. Completion thread of CS2 executed complete_multi_cs before
   completion of CS 3 and 4 and so will trigger the multi CS wait of
   CSs 3 and 4 as they wait on master QID 0.

This will trigger multi CS completion although none of its
current CS has been completed.

Fixed by adding multi CS complete handling indication for each CS.
CS will be marked to the user as completed only if its fence completed
and multi CS handling is done.

Signed-off-by: Dani Liberman <dliberman@habana.ai>
Reviewed-by: Oded Gabbay <ogabbay@kernel.org>
Signed-off-by: Oded Gabbay <ogabbay@kernel.org>

0 files changed, 0 insertions, 0 deletions