From: Johan Hedberg <johan.hedberg@xxxxxxxxx>
In certain circumstances, such as an HCI driver using __hci_cmd_sync_ev
with HCI_EV_CMD_COMPLETE as the expected completion event there is the
chance that hci_event_packet will call hci_req_cmd_complete twice (once
for the explicitly looked after event and another time in the actual
handler of cmd_complete).
In the case of __hci_cmd_sync_ev this introduces a race where the first
call wakes up the blocking __hci_cmd_sync_ev and lets it complete.
However, by the time that a second __hci_cmd_sync_ev call is already in
progress the second hci_req_cmd_complete call (from the previous
operation) will wake up the blocking function prematurely and cause it
to fail, as witnessed by the following log:
[ 639.232195] hci_rx_work: hci0 Event packet
[ 639.232201] hci_req_cmd_complete: opcode 0xfc8e status 0x00
[ 639.232205] hci_sent_cmd_data: hci0 opcode 0xfc8e
[ 639.232210] hci_req_sync_complete: hci0 result 0x00
[ 639.232220] hci_cmd_complete_evt: hci0 opcode 0xfc8e
[ 639.232225] hci_req_cmd_complete: opcode 0xfc8e status 0x00
[ 639.232228] __hci_cmd_sync_ev: hci0 end: err 0
[ 639.232234] __hci_cmd_sync_ev: hci0
[ 639.232238] hci_req_add_ev: hci0 opcode 0xfc8e plen 250
[ 639.232242] hci_prepare_cmd: skb len 253
[ 639.232246] hci_req_run: length 1
[ 639.232250] hci_sent_cmd_data: hci0 opcode 0xfc8e
[ 639.232255] hci_req_sync_complete: hci0 result 0x00
[ 639.232266] hci_cmd_work: hci0 cmd_cnt 1 cmd queued 1
[ 639.232271] __hci_cmd_sync_ev: hci0 end: err 0
[ 639.232276] Bluetooth: hci0 sending Intel patch command (0xfc8e) failed (-61)
Signed-off-by: Johan Hedberg <johan.hedberg@xxxxxxxxx>
---
v2: Only set complete callback to NULL if it was not already so
net/bluetooth/hci_core.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
diff --git a/net/bluetooth/hci_core.c b/net/bluetooth/hci_core.c
index b821b19..5b8a8cb 100644
--- a/net/bluetooth/hci_core.c
+++ b/net/bluetooth/hci_core.c
@@ -3399,8 +3399,16 @@ void hci_req_cmd_complete(struct hci_dev *hdev, u16 opcode, u8 status)
*/
if (hdev->sent_cmd) {
req_complete = bt_cb(hdev->sent_cmd)->req.complete;
- if (req_complete)
+
+ if (req_complete) {
+ /* We must set the complete callback to NULL to
+ * avoid calling the callback more than once if
+ * this function gets called again.
+ */
+ bt_cb(hdev->sent_cmd)->req.complete = NULL;
+
goto call_complete;
+ }
}
/* Remove all pending commands belonging to this request */
--
1.8.3.2
--
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