> allocating pages from UVM can call wakeup(), so we must avoid that
> while holding sched_lock.  one way to do this would be to call
> sadata_upcall_alloc() before acquiring sched_lock and passing the
> resulting pointer to sa_switch(), instead of calling that in
> sa_switch() itself.  does anyone have any better suggestions?
> if not, I'll fix it that way.
> 
> -Chuck

i thought there were an effort to allocate upcall data on new lwp's stack.

YAMAMOTO Takashi