Messages in this thread | | | Date | Tue, 30 Apr 2019 10:28:14 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH 5/5] IB/hfi1: Fix improper uses of smp_mb__before_atomic() |
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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(); > if (reserved_used >= rdi->dparms.reserved_operations) > return -ENOMEM; > return 0; > @@ -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);
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