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Date: Sun, 29 Dec 2013 11:21:19 +1100 From: Alex <xor@....bz> To: <linux-kernel@...r.kernel.org> Subject: Re: TSC Problems (warp between CPUs) On 2013-12-29 01:35, One Thousand Gnomes wrote: >> not guaranteed to be precise. For example a SMI (System Management >> Interrupt) could interrupt the software flow that is attempting to >> write >> the time-stamp counter immediately prior to the WRMSR. This could >> mean >> the value written to the TSC could vary by thousands to millions of >> clocks. > > Yes SMI is a disaster area for any real time activity (and many other > things ;) ), but many systems actually make little use of it, > especially > once the USB is owned by the OS. > > For synchronization you can retry the sync if it isn't within an > acceptable range. The odds of getting an SMI mid sync setup should be > very very low, so the odds of repeating the failure several times > should > be negligible and after a few tries you could give up and assume the > hardware is buggered then fall back to HPET. Hi Alan, The sync retry sounds like an interesting strategy but is outside my knowledge scope as a regular end user (I do have a reasonable understanding of C and can patch+ recompile) but I lack the architecture knowledge to implement a patch to do this. Any suggestions? -- Kind Regards, Alex. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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