On 22/04/2015 23:21, Marcelo Tosatti wrote: > On Mon, Apr 20, 2015 at 01:27:58PM -0700, Andy Lutomirski wrote: >> On Mon, Apr 20, 2015 at 9:59 AM, Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote: >>> >>> >>> On 17/04/2015 22:18, Marcelo Tosatti wrote: >>>> The bug which this is fixing is very rare, have no memory of a report. >>>> >>>> In fact, its even difficult to create a synthetic reproducer. >>> >>> But then why was the task migration notifier even in Jeremy's original >>> code for Xen? Was it supposed to work even on non-synchronized TSC? >>> >>> If that's the case, then it could be reverted indeed; but then why did >>> you commit this patch to 4.1? Did you think of something that would >>> cause the seqcount-like protocol to fail, and that turned out not to be >>> the case later? I was only following the mailing list sparsely in March. >> >> I don't think anyone ever tried that hard to test this stuff. There >> was an infinte loop that Firefox was triggering as a KVM guest >> somewhat reliably until a couple months ago in the same vdso code. :( > > https://bugzilla.redhat.com/show_bug.cgi?id=1174664 That was the missing volatile in an asm. Older compilers didn't catch it. :( Paolo -- 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
