On 2011-01-31 11:03, Avi Kivity wrote: > On 01/27/2011 04:33 PM, Jan Kiszka wrote: >> Found by Stefan Hajnoczi: There is a race in kvm_cpu_exec between >> checking for exit_request on vcpu entry and timer signals arriving >> before KVM starts to catch them. Plug it by blocking both timer related >> signals also on !CONFIG_IOTHREAD and process those via signalfd. >> >> As this fix depends on real signalfd support (otherwise the timer >> signals only kick the compat helper thread, and the main thread hangs), >> we need to detect the invalid constellation and abort configure. >> >> Signed-off-by: Jan Kiszka<jan.kis...@siemens.com> >> CC: Stefan Hajnoczi<stefa...@linux.vnet.ibm.com> >> --- >> >> I don't want to invest that much into !IOTHREAD anymore, so let's see if >> the proposed catch&abort is acceptable. >> > > I don't understand the dependency on signalfd. The normal way of doing > things, either waiting for the signal in sigtimedwait() or in > ioctl(KVM_RUN), works with SIGALRM just fine.
And how would you be kicked out of the select() call if it is waiting with a timeout? We only have a single thread here. The only alternative is Stefan's original proposal. But that required fiddling with the signal mask twice per KVM_RUN. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
