On 11/10/05, Jan Hudec <bulb@xxxxxx> wrote: > I don't know about runqueue balancing, at least not by that name, but a > few comments anyway: By that I actually meant *load balancing*, i.e. the balancing of processes among available CPUs, which involves balancing of the runqueues across CPUs (or so it says in linux kernel development). I see that this may be confusing. > It did disable BHs, because the BH can run on any CPU. It depends on > which CPU first reaches point suitable for running the BH. I am not sure > whether it depends on which CPU the interrupt was handled on, but that > can still be any of them. OK, Here I thought because softirq daemons are per processor, the bottom halves associated would be per processor, too. But I see that there's no such guarantee. Also interrupts would most likely be arbitrated among CPUs, and there's no guarantee that they run on a particular CPU, unless the HW is set up to do otherwise. > I think I understand now. Process can only ever move from one CPU to > another when it's sleeping (or more precisly, when it's being taken out > of the runqueue during a scheduling pass). And a process holding > spinlock can't be put to sleep. So it can't be moved to another CPU. > Jan 'Bulb' Hudec <bulb@xxxxxx> I think this explains why the scenario doesn't deadlock. Thanks, Bahadir -- Kernelnewbies: Help each other learn about the Linux kernel. Archive: http://mail.nl.linux.org/kernelnewbies/ FAQ: http://kernelnewbies.org/faq/
