On Mon, Apr 29, 2019 at 10:15:01PM +0200, Andrea Parri wrote:
This barrier only applies to the read-modify-write operations; in particular, it does not apply to the atomic_read() primitive.
Replace the barrier with an smp_mb().
Fixes: 856cc4c237add ("IB/hfi1: Add the capability for reserved operations") Cc: stable@vger.kernel.org Reported-by: "Paul E. McKenney" paulmck@linux.ibm.com Reported-by: Peter Zijlstra peterz@infradead.org Signed-off-by: Andrea Parri andrea.parri@amarulasolutions.com Cc: Dennis Dalessandro dennis.dalessandro@intel.com Cc: Mike Marciniszyn mike.marciniszyn@intel.com Cc: Doug Ledford dledford@redhat.com Cc: Jason Gunthorpe jgg@ziepe.ca Cc: linux-rdma@vger.kernel.org
drivers/infiniband/sw/rdmavt/qp.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/infiniband/sw/rdmavt/qp.c b/drivers/infiniband/sw/rdmavt/qp.c index a34b9a2a32b60..b64fd151d31fb 100644 --- a/drivers/infiniband/sw/rdmavt/qp.c +++ b/drivers/infiniband/sw/rdmavt/qp.c @@ -1863,11 +1863,11 @@ static inline int rvt_qp_is_avail( u32 reserved_used; /* see rvt_qp_wqe_unreserve() */
I see a completely bogus comment in rvf_op_wqe_unreserve(), referring to bogus comments makes this barrier bogus too.
- smp_mb__before_atomic();
- smp_mb(); reserved_used = atomic_read(&qp->s_reserved_used); if (unlikely(reserved_op)) { /* see rvt_qp_wqe_unreserve() */
smp_mb__before_atomic();
This was before, but there is nothing _after_ this. Which means this barrier was complete garbage anyway.
smp_mb();@@ -1882,7 +1882,7 @@ static inline int rvt_qp_is_avail( avail = slast - qp->s_head; /* see rvt_qp_wqe_unreserve() */
- smp_mb__before_atomic();
- smp_mb();
Same as the first.
reserved_used = atomic_read(&qp->s_reserved_used); avail = avail - 1 - (rdi->dparms.reserved_operations - reserved_used);