Also curious why the kernel can't abandon the thread since the process is dead anyway; set a bit in kernel space so on the walk back from the syscall it bails out instead of trying to return to userspace.
That doesn't solve the kernel thread being stuck forever problem. I'm not sure what the fix is there... is it bad drivers with no timeout mechanism? I don't know how they'd do that unless the kernel IO is all async anyway. Just tearing down the kernel thread seems likely to leave the locks abandoned in bad states.
The kernel can't abandon that thread entirely, but it could "detach" it from the process it was part of and arrange for it to clean itself up and disappear if ever it wakes. And so the parent process could get told of the child's death.
That doesn't solve the kernel thread being stuck forever problem. I'm not sure what the fix is there... is it bad drivers with no timeout mechanism? I don't know how they'd do that unless the kernel IO is all async anyway. Just tearing down the kernel thread seems likely to leave the locks abandoned in bad states.