On Fri, 22 Jun 2018, Michal Hocko wrote: > > > preempt_disable() is required because it calls kvm_kick_many_cpus() with > > > wait == true because KVM_REQ_APIC_PAGE_RELOAD sets KVM_REQUEST_WAIT and > > > thus the smp_call_function_many() is going to block until all cpus can run > > > ack_flush(). > > > > I will make sure to talk to the maintainer of the respective code to > > do the nonblock case correctly. > > I've just double checked this particular code and the wait path and this > one is not a sleep. It is a busy wait for IPI to get handled. So this > one should be OK AFAICS. Anyway I will send an RFC and involve > respective maintainers to make sure I am not making any incorrect > assumptions. Do you believe that having the only potential source of memory freeing busy waiting for all other cpus on the system to run ack_flush() is particularly dangerous given the fact that they may be allocating themselves?
