Synch question 2.6.x

Hi,
 I have this 2.6.x kernel mode component for which I have question regarding
the synch reqmt. between workqueues (or tasklets) and kernel threads. The
kernel threads are created from within the kernel module and there is no
user-mode side to them.

 I share some global data in the kernel space that is accessed by the kernel
thread and a work queue (or a tasklet) (kicked off of an isr top-half and
also off of a kernel thread).

 Is there a need to synch access to this data if the preemption is off. What
if the premption is turned on?

 In the case of workq's, if the synch is reqd, are down_xx() up_xx(),
primitives the right ones to use?

Thanks much in advance.

_Srinivas