On Tue, Apr 15, 2025, Andrew Cooper wrote: > On 11/04/2025 10:40 pm, Sean Christopherson wrote: > > On Thu, Apr 10, 2025, Ross Philipson wrote: > >> + * instruction can return for a number of reasons. Test to see if it returned > >> + * because the monitor was written to. > >> + */ > >> + monitor > >> + > >> +1: > >> + mfence > >> + mwait > >> + movl (%eax), %edx > > Why load the value into EDX? At a glance, the value is never consumed. > > > >> + testl %edx, %edx > >> + jz 1b > > This usage of MONITOR/MWAIT is flawed. The monitor needs to be re-armed in each > > loop, otherwise mwait will be a glorified nop. > > > > More importantly, the exit condition needs to be checked before monitor, > > after monitor and before mwait. Gah, yeah, I mean to say "before mwait".
