While building Lustre master on CentOS 6.5 with 2.6.32-431.el6 kernel and OFED 3.12-1 we get a build error:

[ 212s] In file included from /home/abuild/rpmbuild/BUILD/cray-lustre/lnet/klnds/o2iblnd/o2iblnd.h:82,
[ 212s] from /home/abuild/rpmbuild/BUILD/cray-lustre/lnet/klnds/o2iblnd/o2iblnd.c:42:
[ 212s] /home/abuild/rpmbuild/BUILD/cray-lustre/lnet/include/lnet/lib-lnet.h:708: error: redefinition of 'sk_sleep'
[ 212s] /usr/src/kernel-modules-ofed/x86_64/cray_ari_s_cos/include/linux/compat-2.6.35.h:41: note: previous definition of 'sk_sleep' was here

The kernel is not providing sk_sleep:
[ 146s] checking if Linux kernel has 'sk_sleep'... no

So it appears that the compat header from OFED defines sk_sleep, then later lnet/include/lnet/lib-lnet.h checks if the kernel provides sk_sleep and defines sk_sleep again if the kernel doesn't.