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Kernel prepatch 3.5-rc5Kernel prepatch 3.5-rc5Posted Jul 1, 2012 20:14 UTC (Sun) by Tobu (subscriber, #24111)In reply to: Kernel prepatch 3.5-rc5 by theophrastus Parent article: Kernel prepatch 3.5-rc5 Apparently the bug was noticed (presumably some forward-looking organisations do run tests with clocks running a few months fast) and fixed in 3.4 but not publicised and not CC-ed to stable. So there's a process problem in that the test->publicise loop wasn't closed. And the bug wasn't noticed after it was pulled in 2008, presumably because no one ran leap second tests that flagged an abnormally high cpu load.
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Leap seconds & the kernel Posted Jul 1, 2012 20:27 UTC (Sun) by Tobu (subscriber, #24111) [Link] Except there was a leap second in December 2008, so there's more to it than that.
Leap seconds & the kernel Posted Jul 1, 2012 20:31 UTC (Sun) by Cyberax (✭ supporter ✭, #52523) [Link]
And we had kernel crashes back then on loaded systems :)
Well, at least we're safe for 3-4 more years.
Leap seconds & the kernel Posted Jul 1, 2012 20:55 UTC (Sun) by theophrastus (guest, #80847) [Link]
I guess what i was hoping for - and thankee for any insights! - was more along the lines of: "...process_table scheduler counts up to a hardwired 86,400 and then increments day_count..." ? and/or what does Java have to do with it? (as various reports have reported)
Leap seconds & the kernel Posted Jul 1, 2012 21:09 UTC (Sun) by Cyberax (✭ supporter ✭, #52523) [Link]
No, it's more like "incremental seconds counter and absolute time diverge in an unexpected way".
Leap seconds & the kernel Posted Jul 1, 2012 22:03 UTC (Sun) by alankila (subscriber, #47141) [Link]
Given that wide array of programs were affected, not just java, it was a more general issue. Apparently futexes immediately timeouted after the leap second was applied, and this caused high CPU usage.
The freakish thing was that just restarting the affected program did not fix it. I'm still waiting for the full LWN exposé of this particular issue...
Leap seconds & the kernel Posted Jul 2, 2012 8:54 UTC (Mon) by Cyberax (✭ supporter ✭, #52523) [Link]
Looks like the problem has been identified: http://article.gmane.org/gmane.linux.kernel/1321284
Oh well, I guess I'll wait 4 more years to see if it's fixed by that time :)
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