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Andrew Cooper
496673a2ad
In a 32bit build, the ocaml code 'proposed_id >= 0x7fffffff' compiles to: 8055eac: 83 fb ff cmp $0xffffffff,%ebx 8055eaf: 7d 0f jge 8055ec0 <...+0x20> which in C is 'proposed_id >= INT_MIN', or in other words, tautologically true. As a result, 32bit builds of oxenstored always try to allocate the transaction id 1, and fall into an infinite loop of trying the next id if transaction 1 is already in use. Restrict the range down to 1 billion, to sit in the positive half of a 31 bit ocaml integer. The compiled code is now: 8055eac: b9 ff ff ff 7f mov $0x7fffffff,%ecx 8055eb1: 39 cb cmp %ecx,%ebx 8055eb3: 7d 0b jge 8055ec0 <...+0x20> which (other than non-optimal code generation because of the unnecessary use of %ecx), isn't unconditionally true. In principle, the check could be changed to 'proposed_id == 0x7fffffff' which would still allow for 2 billion transaction in 32bit builds. However, in 64bit builds, this reintroduces a risk that if proposed_id is initially greater than 0x7fffffff, it will not be clipped suitably into range. Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com> Reviewed-by: Wei Liu <wei.liu2@citrix.com> Acked-by: David Scott <dave@recoil.org> Release-acked-by: Wei Liu <wei.liu2@citrix.com>