Messages in this thread | | | Date | Sat, 1 Nov 2008 12:14:41 -0400 (EDT) | From | Alan Stern <> | 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?
| |