On Fri, 2008-05-02 at 05:42 -0700, Paul E. McKenney wrote: > And here is one scenario that makes me doubt that my imagination is > faulty: > > 1. CPU 0 disables irqs. > > 2. CPU 1 disables irqs. > > 3. CPU 0 invokes smp_call_function(). But CPU 1 will never respond > because its irqs are disabled. > > 4. CPU 1 invokes smp_call_function(). But CPU 0 will never respond > because its irqs are disabled. > > Looks like inherent deadlock to me, requiring that smp_call_function() > be invoked with irqs enabled. > > So, what am I missing here? The wish to do it anyway ;-) I can imagine some situations where I'd like to try anyway and fall back to a slower path when failing. With the initial design we would simply allocate data, stick it on the queue and call the ipi (when needed). This is perfectly deadlock free when wait=0 and it just returns -ENOMEM on allocation failure. It it doesn't return -ENOMEM I know its been queued and will be processed at some point, if it does fail, I can deal with it in another way. I know I'd like to do that and I suspect Nick has a few use cases up his sleeve as well. -- To unsubscribe from this list: send the line "unsubscribe linux-arch" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
