From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Marciniszyn Subject: [PATCH 1/4] IB/qib: remove atomic_inc_not_zero from QP RCU Date: Sat, 15 Jun 2013 17:06:58 -0400 Message-ID: <20130615210658.6069.20770.stgit@phlsvslse11.ph.intel.com> References: <20130615210633.6069.14865.stgit@phlsvslse11.ph.intel.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20130615210633.6069.14865.stgit-K+u1se/DcYrLESAwzcoQNrvm/XP+8Wra@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: roland-BHEL68pLQRGGvPXPguhicg@public.gmane.org Cc: linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org Follow Documentation/RCU/rcuref.txt guidance in removing atomic_inc_not_zero() from QP RCU implementation. This patch also removes an unneeded synchronize_rcu() in the add path. Reviewed-by: Dean Luick Signed-off-by: Mike Marciniszyn --- drivers/infiniband/hw/qib/qib_qp.c | 29 +++++++++++++++-------------- 1 file changed, 15 insertions(+), 14 deletions(-) diff --git a/drivers/infiniband/hw/qib/qib_qp.c b/drivers/infiniband/hw/qib/qib_qp.c index a6a2cc2..c1f573a 100644 --- a/drivers/infiniband/hw/qib/qib_qp.c +++ b/drivers/infiniband/hw/qib/qib_qp.c @@ -1,5 +1,5 @@ /* - * Copyright (c) 2012 Intel Corporation. All rights reserved. + * Copyright (c) 2012, 2013 Intel Corporation. All rights reserved. * Copyright (c) 2006 - 2012 QLogic Corporation. * All rights reserved. * Copyright (c) 2005, 2006 PathScale, Inc. All rights reserved. * @@ -222,8 +222,8 @@ static void insert_qp(struct qib_ibdev *dev, struct qib_qp *qp) unsigned long flags; unsigned n = qpn_hash(dev, qp->ibqp.qp_num); - spin_lock_irqsave(&dev->qpt_lock, flags); atomic_inc(&qp->refcount); + spin_lock_irqsave(&dev->qpt_lock, flags); if (qp->ibqp.qp_num == 0) rcu_assign_pointer(ibp->qp0, qp); @@ -235,7 +235,6 @@ static void insert_qp(struct qib_ibdev *dev, struct qib_qp *qp) } spin_unlock_irqrestore(&dev->qpt_lock, flags); - synchronize_rcu(); } /* @@ -247,36 +246,39 @@ static void remove_qp(struct qib_ibdev *dev, struct qib_qp *qp) struct qib_ibport *ibp = to_iport(qp->ibqp.device, qp->port_num); unsigned n = qpn_hash(dev, qp->ibqp.qp_num); unsigned long flags; + int removed = 1; spin_lock_irqsave(&dev->qpt_lock, flags); if (rcu_dereference_protected(ibp->qp0, lockdep_is_held(&dev->qpt_lock)) == qp) { - atomic_dec(&qp->refcount); rcu_assign_pointer(ibp->qp0, NULL); } else if (rcu_dereference_protected(ibp->qp1, lockdep_is_held(&dev->qpt_lock)) == qp) { - atomic_dec(&qp->refcount); rcu_assign_pointer(ibp->qp1, NULL); } else { struct qib_qp *q; struct qib_qp __rcu **qpp; + removed = 0; qpp = &dev->qp_table[n]; for (; (q = rcu_dereference_protected(*qpp, lockdep_is_held(&dev->qpt_lock))) != NULL; qpp = &q->next) if (q == qp) { - atomic_dec(&qp->refcount); rcu_assign_pointer(*qpp, rcu_dereference_protected(qp->next, lockdep_is_held(&dev->qpt_lock))); + removed = 1; break; } } spin_unlock_irqrestore(&dev->qpt_lock, flags); - synchronize_rcu(); + if (removed) { + synchronize_rcu(); + atomic_dec(&qp->refcount); + } } /** @@ -334,26 +336,25 @@ struct qib_qp *qib_lookup_qpn(struct qib_ibport *ibp, u32 qpn) { struct qib_qp *qp = NULL; + rcu_read_lock(); if (unlikely(qpn <= 1)) { - rcu_read_lock(); if (qpn == 0) qp = rcu_dereference(ibp->qp0); else qp = rcu_dereference(ibp->qp1); + if (qp) + atomic_inc(&qp->refcount); } else { struct qib_ibdev *dev = &ppd_from_ibp(ibp)->dd->verbs_dev; unsigned n = qpn_hash(dev, qpn); - rcu_read_lock(); for (qp = rcu_dereference(dev->qp_table[n]); qp; qp = rcu_dereference(qp->next)) - if (qp->ibqp.qp_num == qpn) + if (qp->ibqp.qp_num == qpn) { + atomic_inc(&qp->refcount); break; + } } - if (qp) - if (unlikely(!atomic_inc_not_zero(&qp->refcount))) - qp = NULL; - rcu_read_unlock(); return qp; } -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html