[tip:core/rcu] drivers/net/ethernet/qlogic/qed: Fix __qed_spq_block() ordering

[tip:core/rcu] drivers/net/ethernet/qlogic/qed: Fix __qed_spq_block() ordering

[tip-bot for Paul E. McKenney]

Commit-ID:  cb7e125e03274cffa97d74433c876765efffaf6a
Gitweb:     https://git.kernel.org/tip/cb7e125e03274cffa97d74433c876765efffaf6a
Author:     Paul E. McKenney <paulmck@linux.vnet.ibm.com>
AuthorDate: Mon, 9 Oct 2017 09:26:25 -0700
Committer:  Paul E. McKenney <paulmck@linux.vnet.ibm.com>
CommitDate: Mon, 4 Dec 2017 10:52:52 -0800

drivers/net/ethernet/qlogic/qed: Fix __qed_spq_block() ordering

The __qed_spq_block() function expects an smp_read_barrier_depends()
to order a prior READ_ONCE() against a later load that does not depend
on the prior READ_ONCE(), an expectation that can fail to be met.
This commit therefore replaces the READ_ONCE() with smp_load_acquire()
and removes the smp_read_barrier_depends().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Ariel Elior <Ariel.Elior@cavium.com>
Cc: <everest-linux-l2@cavium.com>
Cc: <netdev@vger.kernel.org>
---
 drivers/net/ethernet/qlogic/qed/qed_spq.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)

diff --git a/drivers/net/ethernet/qlogic/qed/qed_spq.c b/drivers/net/ethernet/qlogic/qed/qed_spq.c
index be48d9a..c1237ec 100644
--- a/drivers/net/ethernet/qlogic/qed/qed_spq.c
+++ b/drivers/net/ethernet/qlogic/qed/qed_spq.c
@@ -97,9 +97,7 @@ static int __qed_spq_block(struct qed_hwfn *p_hwfn,
 
 	while (iter_cnt--) {
 		/* Validate we receive completion update */
-		if (READ_ONCE(comp_done->done) == 1) {
-			/* Read updated FW return value */
-			smp_read_barrier_depends();
+		if (smp_load_acquire(&comp_done->done) == 1) { /* ^^^ */
 			if (p_fw_ret)
 				*p_fw_ret = comp_done->fw_return_code;
 			return 0;