2018-11-27 12:24:12

by Andrea Parri

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 <[email protected]>
---
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

2018-12-18 23:52:11

by Marcel Holtmann

Subject: Re: [PATCH] bluetooth: Remove unnecessary smp_mb__after_atomic() barriers

Hi Andrea,

> 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 <[email protected]>
> ---
> drivers/bluetooth/btusb.c | 8 ++------
> drivers/bluetooth/hci_intel.c | 16 ++++------------
> 2 files changed, 6 insertions(+), 18 deletions(-)

patch has been applied to bluetooth-next tree.

Regards

Marcel