op 14-05-14 17:29, Christian K?nig schreef:
>> + /* did fence get signaled after we enabled the sw irq? */
>> + if (atomic64_read(&fence->rdev->fence_drv[fence->ring].last_seq) >=
>> fence->seq) {
>> + radeon_irq_kms_sw_irq_put(fence->rdev, fence->ring);
>> + return false;
>> + }
>> +
>> + fence->fence_wake.flags = 0;
>> + fence->fence_wake.private = NULL;
>> + fence->fence_wake.func = radeon_fence_check_signaled;
>> + __add_wait_queue(&fence->rdev->fence_queue, &fence->fence_wake);
>> + fence_get(f);
> That looks like a race condition to me. The fence needs to be added to the
> wait queue before the check, not after.
>
> Apart from that the whole approach looks like a really bad idea to me. How
> for example is lockup detection supposed to happen with this?
It's not a race condition because fence_queue.lock is held when this function
is called.
Lockup's a bit of a weird problem, the changes wouldn't allow core ttm code to
handle the lockup any more,
but any driver specific wait code would still handle this. I did this by
design, because in future patches the wait
function may be called from outside of the radeon driver. The official wait
function takes a timeout parameter,
so lockups wouldn't be fatal if the timeout is set to something like 30*HZ for
example, it would still return
and report that the function timed out.
~Maarten
