Hi Daniel, > In __hci_req_enable_advertising, the HCI_LE_ADV hdev flag is temporarily > cleared to allow the random address to be set, which exposes a race > condition when an advertisement is configured immediately (<10ms) after > software rotation starts to refresh an advertisement. > > In normal operation, the HCI_LE_ADV flag is updated as follows: > > 1. adv_timeout_expire is called, HCI_LE_ADV gets cleared in > __hci_req_enable_advertising, but hci_req configures an enable > request > 2. hci_req is run, enable callback re-sets HCI_LE_ADV flag > > However, in this race condition, the following occurs: > > 1. adv_timeout_expire is called, HCI_LE_ADV gets cleared in > __hci_req_enable_advertising, but hci_req configures an enable > request > 2. add_advertising is called, which also calls > __hci_req_enable_advertising. Because HCI_LE_ADV was cleared in Step > 1, no "disable" command is queued. > 3. hci_req for adv_timeout_expire is run, which enables advertising and > re-sets HCI_LE_ADV > 4. hci_req for add_advertising is run, but because no "disable" command > was queued, we try to set advertising parameters while advertising is > active, causing a Command Disallowed error, failing the registration. > > To resolve the issue, this patch removes the check for the HCI_LE_ADV > flag, and always queues the "disable" request, since HCI_LE_ADV could be > very temporarily out-of-sync. According to the spec, there is no harm in > calling "disable" when advertising is not active. > > Reviewed-by: Miao-chen Chou <mcchou@xxxxxxxxxxxx> > Signed-off-by: Daniel Winkler <danielwinkler@xxxxxxxxxx> > --- > > net/bluetooth/hci_request.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/net/bluetooth/hci_request.c b/net/bluetooth/hci_request.c > index 8ace5d34b01efe..2b4b99f4cedf21 100644 > --- a/net/bluetooth/hci_request.c > +++ b/net/bluetooth/hci_request.c > @@ -1547,8 +1547,10 @@ void __hci_req_enable_advertising(struct hci_request *req) > if (!is_advertising_allowed(hdev, connectable)) > return; > > - if (hci_dev_test_flag(hdev, HCI_LE_ADV)) > - __hci_req_disable_advertising(req); > + /* Request that the controller stop advertising. This can be called > + * whether or not there is an active advertisement. > + */ > + __hci_req_disable_advertising(req); can you include a btmon trace that shows that we don’t get a HCI error. Since if we get one, then the complete request will fail. And that has further side effects. Regards Marcel
