On Jan 26, 2010, at 12:09 PM, M. Warner Losh wrote:
> cpu_switch(struct thread *old, struct thread *new, struct mutext *mtx)
> {
> /* Save the registers to the pcb */
> old->td_lock = mtx;
> #if defined(SMP) && defined(SCHED_ULE)
> /* s/long/int/ if sizeof(long) != sizeof(void *) */
> /* as we have no 'void *' version of the atomics */
> while (atomic_load_acq_long(&new->td_lock) == (long)&blocked_lock)
> continue;
> #endif
> /* Switch to new context */
> }
Ok. So this is what ia64 has already, except for the atomic_load()
in the while loop. Since td_lock is volatile, I don't think we need
atomic_load(). To be explicit, ia64 has:
old->td_lock = mtx;
#if defined(SCHED_ULE) && defined(SMP)
/* td_lock is volatile */
while (new->td_lock == &blocked_lock)
;
#endif
Am I right, or am I missing a critical aspect of using atomic load?
> I also think that we should have that code somewhere for reference.
Since ia64 has a C implementation of cpu_switch(), we could make
that the reference implementation?
--
Marcel Moolenaar
xcl...@mac.com
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