Am 16.09.2015 um 09:44 schrieb Christian Borntraeger: > Am 16.09.2015 um 03:24 schrieb Tejun Heo: >> Hello, Paul. >> >> On Tue, Sep 15, 2015 at 04:38:18PM -0700, Paul E. McKenney wrote: >>> Well, the decision as to what is too big for -stable is owned by the >>> -stable maintainers, not by me. >> >> Is it tho? Usually the subsystem maintainer knows the best and has >> most say in it. I was mostly curious whether you'd think that the >> changes would be too risky. If not, great. >> >>> I am suggesting trying the options and seeing what works best, then >>> working to convince people as needed. >> >> Yeah, sure thing. Let's wait for Christian. > > Well, I have optimized my testcase now that is puts enough pressure to > the system to confuses system (the older 209 version, which still has > some event loop issues) that systemd restarts the journal deamon and does > several other recoveries. > To avoid regressions - even for somewhat shaky userspaces - we should > consider a revert for 4.2 stable. > There are several followup patches, which makes the revert non-trivial, > though. > > The rework of the percpu rwsem seems to work fine, but we are beyond the > merge window so 4.4 seems better to me. (and consider a revert for 4.3) FWIW, I added a printk to percpu_down_write. With KVM and uprobes disabled, just booting up a fedora20 gives me __6749__ percpu_down_write calls on 4.2. systemd seems to do that for the processes. So a revert is really the right thing to do. In fact, I dont know if the rcu_sync_enter rework is enough. With systemd setting the cgroup seem to be NOT a cold/seldom case. Christian -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
