[Back to the powerpc64 context.] On 2017-Feb-20, at 11:10 AM, Mateusz Guzik <mjgu...@gmail.com> wrote:
> On Sat, Feb 18, 2017 at 04:18:05AM -0800, Mark Millard wrote: >> [Note: I experiment with clang based powerpc64 builds, >> reporting problems that I find. Justin is familiar >> with this, as is Nathan.] >> >> I tried to update the PowerMac G5 (a so-called "Quad Core") >> that I have access to from head -r312761 to -r313864 and >> ended up with random panics and hang ups in fairly short >> order after booting. >> >> Some approximate bisecting for the kernel lead to: >> (sometimes getting part way into a buildkernel attempt >> for a different version before a failure happens) >> >> -r313266: works (just before use of atomic_fcmpset) >> vs. >> -r313271: fails (last of the "use atomic_fcmpset" check-ins) >> >> (I did not try -r313268 through -r313270 as the use was >> gradually added.) >> >> So I'm currently running a -r313864 world with a -r313266 >> kernel. >> >> No kernel that I tried that was from before -r313266 had the >> problems. >> >> Any kernel that I tried that was from after -r313271 had the >> problems. >> >> Of course I did not try them all in other direction. :) >> > > I found that spin mutexes were not properly handling this, fixed in > r313996. > > Locally I added a if (cpu_tick() % 2) return (0); snipped to amd64 > fcmpset to simulate failures. Everything works, while it would easily > fail without the patch. > > That said, I hope this concludes the 'missing check for not-reread value > of failed fcmpset' saga. > > -- > Mateusz Guzik <mjguzik gmail.com> -r313999 is an improvement for powerpc64: it boots and I can log in on the old PowerMac G5 so-called "Quad Core". But, e.g., buildworld buildkernel eventually hangs and later the powerpc64 panics for "spin lock held too long". === Mark Millard markmi at dsl-only.net _______________________________________________ firstname.lastname@example.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"