Hi Johan, > 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(-) Acked-by: Marcel Holtmann <marcel@xxxxxxxxxxxx> Regards Marcel -- To unsubscribe from this list: send the line "unsubscribe linux-bluetooth" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
