> So if, after this, we run tsc_sched_clock() with an unstable TSC, we > read a last_val containing the interrupt's MSB and the last_val LSB. It > can particularity hurt if we are around a 32 bits overflow, because time > could "jump" forward of about 1.43 seconds on a 3 GHz system. > > So I guess we need synchronization on the fast path, and therefore using > cmpxchg_local on x86_64
On x86-64 the 64bit write is atomic against interrupts. You're right 32bit has a problem though. I'm not too happy about cmpxchg though because that wouldn't work on some CPUs. I wonder if we can just get away with using a 32bit value on i386. Just for the purpose of keeping the value monotonic it should be good enough. Will think about it. Thanks for the review. -Andi - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
