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Message-ID: <312a1cc3-bf55-443e-baad-fd35fede40c8@amlogic.com>
Date: Fri, 27 Jun 2025 19:31:25 +0800
From: Yang Li <yang.li@...ogic.com>
To: Luiz Augusto von Dentz <luiz.dentz@...il.com>
Cc: Pauli Virtanen <pav@....fi>, Marcel Holtmann <marcel@...tmann.org>,
Johan Hedberg <johan.hedberg@...il.com>,
"David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
Simon Horman <horms@...nel.org>, linux-bluetooth@...r.kernel.org,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] Bluetooth: hci_event: Add support for handling LE BIG
Sync Lost event
Hi Luiz,
> [ EXTERNAL EMAIL ]
>
> Hi Yang,
>
> On Thu, Jun 26, 2025 at 1:54 AM Yang Li <yang.li@...ogic.com> wrote:
>> Hi Pauli,
>>> [ EXTERNAL EMAIL ]
>>>
>>> Hi,
>>>
>>> ke, 2025-06-25 kello 16:42 +0800, Yang Li via B4 Relay kirjoitti:
>>>> From: Yang Li <yang.li@...ogic.com>
>>>>
>>>> When the BIS source stops, the controller sends an LE BIG Sync Lost
>>>> event (subevent 0x1E). Currently, this event is not handled, causing
>>>> the BIS stream to remain active in BlueZ and preventing recovery.
>>>>
>>>> Signed-off-by: Yang Li <yang.li@...ogic.com>
>>>> ---
>>>> Changes in v2:
>>>> - Matching the BIG handle is required when looking up a BIG connection.
>>>> - Use ev->reason to determine the cause of disconnection.
>>>> - Call hci_conn_del after hci_disconnect_cfm to remove the connection entry
>>>> - Delete the big connection
>>>> - Link to v1: https://lore.kernel.org/r/20250624-handle_big_sync_lost_event-v1-1-c32ce37dd6a5@amlogic.com
>>>> ---
>>>> include/net/bluetooth/hci.h | 6 ++++++
>>>> net/bluetooth/hci_event.c | 31 +++++++++++++++++++++++++++++++
>>>> 2 files changed, 37 insertions(+)
>>>>
>>>> diff --git a/include/net/bluetooth/hci.h b/include/net/bluetooth/hci.h
>>>> index 82cbd54443ac..48389a64accb 100644
>>>> --- a/include/net/bluetooth/hci.h
>>>> +++ b/include/net/bluetooth/hci.h
>>>> @@ -2849,6 +2849,12 @@ struct hci_evt_le_big_sync_estabilished {
>>>> __le16 bis[];
>>>> } __packed;
>>>>
>>>> +#define HCI_EVT_LE_BIG_SYNC_LOST 0x1e
>>>> +struct hci_evt_le_big_sync_lost {
>>>> + __u8 handle;
>>>> + __u8 reason;
>>>> +} __packed;
>>>> +
>>>> #define HCI_EVT_LE_BIG_INFO_ADV_REPORT 0x22
>>>> struct hci_evt_le_big_info_adv_report {
>>>> __le16 sync_handle;
>>>> diff --git a/net/bluetooth/hci_event.c b/net/bluetooth/hci_event.c
>>>> index 66052d6aaa1d..d0b9c8dca891 100644
>>>> --- a/net/bluetooth/hci_event.c
>>>> +++ b/net/bluetooth/hci_event.c
>>>> @@ -7026,6 +7026,32 @@ static void hci_le_big_sync_established_evt(struct hci_dev *hdev, void *data,
>>>> hci_dev_unlock(hdev);
>>>> }
>>>>
>>>> +static void hci_le_big_sync_lost_evt(struct hci_dev *hdev, void *data,
>>>> + struct sk_buff *skb)
>>>> +{
>>>> + struct hci_evt_le_big_sync_lost *ev = data;
>>>> + struct hci_conn *bis, *conn;
>>>> +
>>>> + bt_dev_dbg(hdev, "big handle 0x%2.2x", ev->handle);
>>>> +
>>>> + hci_dev_lock(hdev);
>>>> +
>>>> + list_for_each_entry(bis, &hdev->conn_hash.list, list) {
>>> This should check bis->type == BIS_LINK too.
>> Will do.
>>>> + if (test_and_clear_bit(HCI_CONN_BIG_SYNC, &bis->flags) &&
>>>> + (bis->iso_qos.bcast.big == ev->handle)) {
>>>> + hci_disconn_cfm(bis, ev->reason);
>>>> + hci_conn_del(bis);
>>>> +
>>>> + /* Delete the big connection */
>>>> + conn = hci_conn_hash_lookup_pa_sync_handle(hdev, bis->sync_handle);
>>>> + if (conn)
>>>> + hci_conn_del(conn);
>>> Problems:
>>>
>>> - use after free
>>>
>>> - hci_conn_del() cannot be used inside list_for_each_entry()
>>> of the connection list
>>>
>>> - also list_for_each_entry_safe() allows deleting only the iteration
>>> cursor, so some restructuring above is needed
>> Following your suggestion, I updated the hci_le_big_sync_lost_evt function.
>>
>> +static void hci_le_big_sync_lost_evt(struct hci_dev *hdev, void *data,
>> + struct sk_buff *skb)
>> +{
>> + struct hci_evt_le_big_sync_lost *ev = data;
>> + struct hci_conn *bis, *conn, *n;
>> +
>> + bt_dev_dbg(hdev, "big handle 0x%2.2x", ev->handle);
>> +
>> + hci_dev_lock(hdev);
>> +
>> + /* Delete the pa sync connection */
>> + bis = hci_conn_hash_lookup_pa_sync_big_handle(hdev, ev->handle);
>> + if (bis) {
>> + conn = hci_conn_hash_lookup_pa_sync_handle(hdev,
>> bis->sync_handle);
>> + if (conn)
>> + hci_conn_del(conn);
>> + }
>> +
>> + /* Delete each bis connection */
>> + list_for_each_entry_safe(bis, n, &hdev->conn_hash.list, list) {
>> + if (bis->type == BIS_LINK &&
>> + bis->iso_qos.bcast.big == ev->handle &&
>> + test_and_clear_bit(HCI_CONN_BIG_SYNC, &bis->flags)) {
>> + hci_disconn_cfm(bis, ev->reason);
>> + hci_conn_del(bis);
>> + }
>> + }
> Id follow the logic in hci_le_create_big_complete_evt, so you do something like:
>
> while ((conn = hci_conn_hash_lookup_big_state(hdev, ev->handle,
> BT_CONNECTED)))...
>
> That way we don't operate on the list cursor, that said we may need to
> add the role as parameter to hci_conn_hash_lookup_big_state, because
> the BIG id domain is role specific so we can have clashes if there are
> Broadcast Sources using the same BIG id the above would return them as
> well and even if we check for the role inside the while loop will keep
> returning it forever.
I updated the patch according to your suggestion; however, during testing, it resulted in a system panic.
hci_conn_hash_lookup_big_state(struct hci_dev *hdev, __u8 handle, __u16 state)
list_for_each_entry_rcu(c, &h->list, list) {
if (c->type != BIS_LINK || bacmp(&c->dst, BDADDR_ANY) ||
+ c->role != HCI_ROLE_SLAVE ||
c->state != state)
continue;
+static void hci_le_big_sync_lost_evt(struct hci_dev *hdev, void *data,
+ struct sk_buff *skb)
+{
+ struct hci_evt_le_big_sync_lost *ev = data;
+ struct hci_conn *bis, *conn;
+
+ bt_dev_dbg(hdev, "big handle 0x%2.2x", ev->handle);
+
+ hci_dev_lock(hdev);
+
+ /* Delete the pa sync connection */
+ bis = hci_conn_hash_lookup_pa_sync_big_handle(hdev, ev->handle);
+ if (bis) {
+ conn = hci_conn_hash_lookup_pa_sync_handle(hdev, bis->sync_handle);
+ if (conn)
+ hci_conn_del(conn);
+ }
+
+ /* Delete each bis connection */
+ while ((bis = hci_conn_hash_lookup_big_state(hdev, ev->handle,
+ BT_CONNECTED))) {
+ clear_bit(HCI_CONN_BIG_SYNC, &bis->flags);
+ hci_disconn_cfm(bis, ev->reason);
+ hci_conn_del(bis);
+ }
+
+ hci_dev_unlock(hdev);
+}
However, during testing, I encountered some issues:
1. The current BIS connections all have the state BT_OPEN (2).
[ 131.813237][1 T1967 d.] list conn 00000000fd2e0fb2, handle 0x0010,
state 1 #LE link
[ 131.813439][1 T1967 d.] list conn 00000000553bfedc, handle 0x0f01,
state 2 #PA link
[ 131.814301][1 T1967 d.] list conn 0000000074213ccb, handle 0x0100,
state 2 #bis1 link
[ 131.815167][1 T1967 d.] list conn 00000000ee6adb18, handle 0x0101,
state 2 #bis2 link
2. hci_conn_hash_lookup_big_state() fails to find the corresponding BIS
connection even when the state is set to OPEN.
Therefore, I’m considering reverting to the original patch, but adding a
role check as an additional condition.
What do you think?
+ /* Delete each bis connection */
+ list_for_each_entry_safe(bis, n, &hdev->conn_hash.list, list) {
+ if (bis->type == BIS_LINK &&
+ bis->role == HCI_ROLE_SLAVE &&
+ bis->iso_qos.bcast.big == ev->handle &&
+ test_and_clear_bit(HCI_CONN_BIG_SYNC, &bis->flags)) {
+ hci_disconn_cfm(bis, ev->reason);
+ hci_conn_del(bis);
+ }
+ }
>
>> +
>> + hci_dev_unlock(hdev);
>> +}
>>
>>>> + }
>>>> + }
>>>> +
>>>> + hci_dev_unlock(hdev);
>>>> +}
>>>> +
>>>> static void hci_le_big_info_adv_report_evt(struct hci_dev *hdev, void *data,
>>>> struct sk_buff *skb)
>>>> {
>>>> @@ -7149,6 +7175,11 @@ static const struct hci_le_ev {
>>>> hci_le_big_sync_established_evt,
>>>> sizeof(struct hci_evt_le_big_sync_estabilished),
>>>> HCI_MAX_EVENT_SIZE),
>>>> + /* [0x1e = HCI_EVT_LE_BIG_SYNC_LOST] */
>>>> + HCI_LE_EV_VL(HCI_EVT_LE_BIG_SYNC_LOST,
>>>> + hci_le_big_sync_lost_evt,
>>>> + sizeof(struct hci_evt_le_big_sync_lost),
>>>> + HCI_MAX_EVENT_SIZE),
>>>> /* [0x22 = HCI_EVT_LE_BIG_INFO_ADV_REPORT] */
>>>> HCI_LE_EV_VL(HCI_EVT_LE_BIG_INFO_ADV_REPORT,
>>>> hci_le_big_info_adv_report_evt,
>>>>
>>>> ---
>>>> base-commit: bd35cd12d915bc410c721ba28afcada16f0ebd16
>>>> change-id: 20250612-handle_big_sync_lost_event-4c7dc64390a2
>>>>
>>>> Best regards,
>>> --
>>> Pauli Virtanen
>
>
> --
> Luiz Augusto von Dentz
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