On Thu, Nov 9, 2017 at 11:35 PM, Jason Gunthorpe <jgg@xxxxxxxx> wrote: > On Thu, Nov 09, 2017 at 06:10:39AM -0500, Devesh Sharma wrote: >> Putting a read barrier before issuing a read on valid bit >> is incorrect. When checking for the validity of CQE in the >> CQ buffer the code must wait for the read-barrier to finish >> after issuing a read operation on CQE valid bit. >> >> Signed-off-by: Devesh Sharma <devesh.sharma@xxxxxxxxxxxx> >> providers/bnxt_re/main.h | 8 ++++++-- >> 1 file changed, 6 insertions(+), 2 deletions(-) > > This is probably fine > >> + uint8_t valid = 0; >> + >> + valid = ((le32toh(hdr->flg_st_typ_ph) & >> + BNXT_RE_BCQE_PH_MASK) == cq->phase); > > Hrm, > > Techincally this should be something like > > le32toh(atomic_read(hdr->flg_st_typ_ph)) > > And the the kernel version of this should be using READ_ONCE() Okay, we will fix this in our driver. So, READ_ONCE(CQE.valid) should be enough right? > > In user space we should probably create a > > udma_from_device_read_once(x) > > That incorporates the barrier and the 'access_once' semantics.. Do you want us to pull all the defined in kernel space compiler.h verbitum to rdma-core I think there would be few changes correct.. > > Jason -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
