netdev - [PATCH] Bluetooth: Don't restart scanning if paused

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Date:   Wed, 24 Jun 2020 11:34:19 -0700
From:   Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
To:     marcel@...tmann.org, linux-bluetooth@...r.kernel.org,
        alainm@...omium.org
Cc:     chromeos-bluetooth-upstreaming@...omium.org,
        Abhishek Pandit-Subedi <abhishekpandit@...omium.org>,
        "David S. Miller" <davem@...emloft.net>,
        Johan Hedberg <johan.hedberg@...il.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        Jakub Kicinski <kuba@...nel.org>
Subject: [PATCH] Bluetooth: Don't restart scanning if paused

When restarting LE scanning, check if it's currently paused before
enabling passive scanning.

Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@...omium.org>
---
When running suspend stress tests on Chromebooks, we discovered
instances where the Chromebook didn't enter the deepest idle states
(i.e. S0ix). After some debugging, we found that passive scanning was
being enabled AFTER the suspend notifier had run (and disabled all
scanning).

For this fix, I simply looked at all the places where we call
HCI_OP_LE_SET_SCAN_ENABLE and added a guard clause for suspend. With
this fix, we were able to get through 100+ iterations of the suspend
stress test without any problems entering S0ix.


 net/bluetooth/hci_request.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/bluetooth/hci_request.c b/net/bluetooth/hci_request.c
index 86ae4b953a011e..116207009dde01 100644
--- a/net/bluetooth/hci_request.c
+++ b/net/bluetooth/hci_request.c
@@ -819,6 +819,11 @@ static void hci_req_start_scan(struct hci_request *req, u8 type, u16 interval,
 {
 	struct hci_dev *hdev = req->hdev;
 
+	if (hdev->scanning_paused) {
+		bt_dev_dbg(hdev, "Scanning is paused for suspend");
+		return;
+	}
+
 	/* Use ext scanning if set ext scan param and ext scan enable is
 	 * supported
 	 */
@@ -2657,6 +2662,11 @@ static int le_scan_restart(struct hci_request *req, unsigned long opt)
 	if (!hci_dev_test_flag(hdev, HCI_LE_SCAN))
 		return 0;
 
+	if (hdev->scanning_paused) {
+		bt_dev_dbg(hdev, "Scanning is paused for suspend");
+		return 0;
+	}
+
 	hci_req_add_le_scan_disable(req);
 
 	if (use_ext_scan(hdev)) {
-- 
2.27.0.111.gc72c7da667-goog