On 01/20/2014 01:16 AM, Peter Zijlstra wrote: >> >> The difference is the STI! > > So do the local_irq_enable(); mwait_idle_with_hints(0,0); thing. > No, that doesn't work. The point of __sti_mwait() is that the STI is the instruction immediately before the MWAIT, just like the combination STI;HLT. Since the execution of STI is always delayed by one instruction, these two instructions form an atomic unit, which means interrupts are enabled "after" we have entered MWAIT or HLT. > But that's entirely different from saying that core2 doesn't support > mwait_idle_with_hints because its a different instruction. If you think of STI;MWAIT as a "compound instruction" it kind of is. Newer CPUs don't have to play that trick anymore, because there is a flag to MWAIT which breaks us out of MWAIT on a pending interrupt without having to actually enable interrupts at the point of the MWAIT. -hpa -- To unsubscribe from this list: send the line "unsubscribe linux-next" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
