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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?



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