Messages in this thread | | | Subject | RE: [PATCH BUGFIX 2/6] pkt_sched: fix the update of eligible-group sets | Date | Wed, 6 Mar 2013 10:05:58 -0000 | From | "David Laight" <> |
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> Between two invocations of make_eligible, the system virtual time may > happen to grow enough that, in its binary representation, a bit with > higher order than 31 flips. This happens especially with > TSO/GSO. Before this fix, the mask used in make_eligible was computed > as (1UL<<index_of_last_flipped_bit)-1, whose value is well defined on > a 64-bit architecture, because index_of_flipped_bit <= 63, but is in > general undefined on a 32-bit architecture if index_of_flipped_bit > 31. > The fix just replaces 1UL with 1ULL. ... > - unsigned long mask = (1UL << fls(vslot ^ old_vslot)) - 1; > + unsigned long mask = (1ULL << fls(vslot ^ old_vslot)) - 1;
I'm not sure you really want to be doing 64bit shifts on 32 bit systems just to generate ~0ul. probably worth a conditional.
David
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