On 04/10/17 03:50 AM, Sebastian Andrzej Siewior wrote:
The poll callback is using completion's wait_queue_head_t member and puts it in poll_wait() so the poll() caller gets a wakeup after command completed. This does not work on RT because we don't have a wait_queue_head_t in our completion implementation. Nobody in tree does like that in tree so this is the only driver that breaks.
I'm sorry but this seems a bit crazy to me. Driver's can't poll on completions because an out of tree implementation changes them in a weird way??! Just because no one in-tree does it now doesn't make it invalid.
But at the very least, if we _absolutely_ have to patch this out, you shouldn't make it so convoluted. Just replace the struct completion with a wait queue and a done flag (which is what a completion is). Don't move the wait queue into switchtec_dev and don't use an unnecessary counter. And certainly don't think about merging it with another wait queue that has completely different wake events and waiters.
In any case, I haven't tested the patch, but I'm pretty sure it's not correct. There can be multiple switchtec_user's queued up and this patch will essentially complete them all once any one of them finishes and cmd_cnt increments.
So this patch gets a NAK from me. Logan
