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Date: Sat, 1 Nov 2008 12:14:41 -0400 (EDT) From: Alan Stern <stern@...land.harvard.edu> To: Andrew Morton <akpm@...ux-foundation.org>, Ingo Molnar <mingo@...hat.com>, Linus Torvalds <torvalds@...ux-foundation.org> cc: Kernel development list <linux-kernel@...r.kernel.org> Subject: (BUG?) round_jiffies() is non-monotonic on SMP Is it generally recognized that round_jiffies() can be non-monotonic on SMP systems? By this, I mean that if cpu-a and cpu-b respectively do: ra = round_jiffies(ja); and rb = round_jiffies(jb); then the ordering of ra and rb can be opposite the ordering of ja and jb. If this is known, is it regarded as a potential problem? It certainly seems likely that some code somewhere depends on timeouts expiring in the correct order. Alan Stern P.S.: As a related matter, it seems very odd that we don't have a round_jiffies_up() routine. Surely there are plenty of places where it doesn't matter if an event is a little late but where the event must not be early. (I know two such places offhand.) Any objection to having one added? -- 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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