linux-kernel - [PATCH] bluetooth: Remove unnecessary smp_mb__after

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Date:   Tue, 27 Nov 2018 12:22:25 +0100
From:   Andrea Parri <andrea.parri@...rulasolutions.com>
To:     Marcel Holtmann <marcel@...tmann.org>,
        Johan Hedberg <johan.hedberg@...il.com>
Cc:     linux-bluetooth@...r.kernel.org, linux-kernel@...r.kernel.org,
        Andrea Parri <andrea.parri@...rulasolutions.com>
Subject: [PATCH] bluetooth: Remove unnecessary smp_mb__after_atomic() barriers

The barriers are redundant because atomic_test_and_clear_bit() already
provides the required full ordering for the cases in question (that is,
when the bit is cleared).

Signed-off-by: Andrea Parri <andrea.parri@...rulasolutions.com>
---
 drivers/bluetooth/btusb.c     |  8 ++------
 drivers/bluetooth/hci_intel.c | 16 ++++------------
 2 files changed, 6 insertions(+), 18 deletions(-)

diff --git a/drivers/bluetooth/btusb.c b/drivers/bluetooth/btusb.c
index 7439a7eb50acb..885e17a1a9a57 100644
--- a/drivers/bluetooth/btusb.c
+++ b/drivers/bluetooth/btusb.c
@@ -1935,10 +1935,8 @@ static void btusb_intel_bootup(struct btusb_data *data, const void *ptr,
 	if (len != sizeof(*evt))
 		return;
 
-	if (test_and_clear_bit(BTUSB_BOOTING, &data->flags)) {
-		smp_mb__after_atomic();
+	if (test_and_clear_bit(BTUSB_BOOTING, &data->flags))
 		wake_up_bit(&data->flags, BTUSB_BOOTING);
-	}
 }
 
 static void btusb_intel_secure_send_result(struct btusb_data *data,
@@ -1953,10 +1951,8 @@ static void btusb_intel_secure_send_result(struct btusb_data *data,
 		set_bit(BTUSB_FIRMWARE_FAILED, &data->flags);
 
 	if (test_and_clear_bit(BTUSB_DOWNLOADING, &data->flags) &&
-	    test_bit(BTUSB_FIRMWARE_LOADED, &data->flags)) {
-		smp_mb__after_atomic();
+	    test_bit(BTUSB_FIRMWARE_LOADED, &data->flags))
 		wake_up_bit(&data->flags, BTUSB_DOWNLOADING);
-	}
 }
 
 static int btusb_recv_event_intel(struct hci_dev *hdev, struct sk_buff *skb)
diff --git a/drivers/bluetooth/hci_intel.c b/drivers/bluetooth/hci_intel.c
index 46ace321bf60e..8caa1a6619cea 100644
--- a/drivers/bluetooth/hci_intel.c
+++ b/drivers/bluetooth/hci_intel.c
@@ -909,10 +909,8 @@ static int intel_recv_event(struct hci_dev *hdev, struct sk_buff *skb)
 			set_bit(STATE_FIRMWARE_FAILED, &intel->flags);
 
 		if (test_and_clear_bit(STATE_DOWNLOADING, &intel->flags) &&
-		    test_bit(STATE_FIRMWARE_LOADED, &intel->flags)) {
-			smp_mb__after_atomic();
+		    test_bit(STATE_FIRMWARE_LOADED, &intel->flags))
 			wake_up_bit(&intel->flags, STATE_DOWNLOADING);
-		}
 
 	/* When switching to the operational firmware the device
 	 * sends a vendor specific event indicating that the bootup
@@ -920,10 +918,8 @@ static int intel_recv_event(struct hci_dev *hdev, struct sk_buff *skb)
 	 */
 	} else if (skb->len == 9 && hdr->evt == 0xff && hdr->plen == 0x07 &&
 		   skb->data[2] == 0x02) {
-		if (test_and_clear_bit(STATE_BOOTING, &intel->flags)) {
-			smp_mb__after_atomic();
+		if (test_and_clear_bit(STATE_BOOTING, &intel->flags))
 			wake_up_bit(&intel->flags, STATE_BOOTING);
-		}
 	}
 recv:
 	return hci_recv_frame(hdev, skb);
@@ -960,17 +956,13 @@ static int intel_recv_lpm(struct hci_dev *hdev, struct sk_buff *skb)
 		break;
 	case LPM_OP_SUSPEND_ACK:
 		set_bit(STATE_SUSPENDED, &intel->flags);
-		if (test_and_clear_bit(STATE_LPM_TRANSACTION, &intel->flags)) {
-			smp_mb__after_atomic();
+		if (test_and_clear_bit(STATE_LPM_TRANSACTION, &intel->flags))
 			wake_up_bit(&intel->flags, STATE_LPM_TRANSACTION);
-		}
 		break;
 	case LPM_OP_RESUME_ACK:
 		clear_bit(STATE_SUSPENDED, &intel->flags);
-		if (test_and_clear_bit(STATE_LPM_TRANSACTION, &intel->flags)) {
-			smp_mb__after_atomic();
+		if (test_and_clear_bit(STATE_LPM_TRANSACTION, &intel->flags))
 			wake_up_bit(&intel->flags, STATE_LPM_TRANSACTION);
-		}
 		break;
 	default:
 		bt_dev_err(hdev, "Unknown LPM opcode (%02x)", lpm->opcode);
-- 
2.17.1