We're running into a situation where concurrent TPM accesses can trigger EBUSY on write due to there either being a queued command or a response not yet having been read. Obviously one approach would be to retry, but that involves us either spinning or waiting for an arbitrary amount of time between attempts, which doesn't seem ideal. There's a poll interface that tells us whether there's a response to read but (a) that doesn't help in the enqueued command situation and (b) this would still be racy - we could be notified that the response has been read, be preempted, and have another process perform a write before we get the opportunity to. What's the right way to fix this? One approach would simply be to replace the EBUSY with an interruptible sleep and wake the process when the TPM is available, but that feels like it's technically an ABI break.
