qed: Fix possible race when reading firmware return code.

While handling SPQ ramrod completion, there is a possible race
where driver might not read updated fw return code based on
ramrod completion done. This patch ensures that fw return code
is written first and then completion done flag is updated
using appropriate memory barriers.

Signed-off-by: Manish Chopra <manish.chopra@caviumnetworks.com>
Signed-off-by: Yuval Mintz <Yuval.Mintz@caviumnetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/ethernet/qlogic/qed/qed_sp.h b/drivers/net/ethernet/qlogic/qed/qed_sp.h
index 652c908197582a09ee648b55706d15bfdedbb372..27c450fd219327e5b291eead936dc3e87d9c9286 100644 (file)
--- a/drivers/net/ethernet/qlogic/qed/qed_sp.h
+++ b/drivers/net/ethernet/qlogic/qed/qed_sp.h
@@ -111,8 +111,8 @@ union qed_spq_req_comp {
 };
 
 struct qed_spq_comp_done {
-       u64     done;
-       u8      fw_return_code;
+       unsigned int    done;
+       u8              fw_return_code;
 };
 
 struct qed_spq_entry {

diff --git a/drivers/net/ethernet/qlogic/qed/qed_spq.c b/drivers/net/ethernet/qlogic/qed/qed_spq.c
index 259a6156c761c0b498f3500e966d9f34ebb695a0..6c05402ea4dca24efdaad579fb78938935f17680 100644 (file)
--- a/drivers/net/ethernet/qlogic/qed/qed_spq.c
+++ b/drivers/net/ethernet/qlogic/qed/qed_spq.c
@@ -54,11 +54,10 @@ static void qed_spq_blocking_cb(struct qed_hwfn *p_hwfn,
 
        comp_done = (struct qed_spq_comp_done *)cookie;
 
-       comp_done->done                 = 0x1;
-       comp_done->fw_return_code       = fw_return_code;
+       comp_done->fw_return_code = fw_return_code;
 
-       /* make update visible to waiting thread */
-       smp_wmb();
+       /* Make sure completion done is visible on waiting thread */
+       smp_store_release(&comp_done->done, 0x1);
 }
 
 static int __qed_spq_block(struct qed_hwfn *p_hwfn,
@@ -74,8 +73,9 @@ static int __qed_spq_block(struct qed_hwfn *p_hwfn,
 
        while (iter_cnt--) {
                /* Validate we receive completion update */
-               smp_rmb();
-               if (comp_done->done == 1) {
+               if (READ_ONCE(comp_done->done) == 1) {
+                       /* Read updated FW return value */
+                       smp_read_barrier_depends();
                        if (p_fw_ret)
                                *p_fw_ret = comp_done->fw_return_code;
                        return 0;