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Message-ID: <CABBYNZKBDiftD_C6LHYpWxrduHe-jNYJp=y+AZo1xXreec1O-g@mail.gmail.com>
Date: Mon, 30 Jun 2025 09:16:43 -0400
From: Luiz Augusto von Dentz <luiz.dentz@...il.com>
To: Yang Li <yang.li@...ogic.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,
On Mon, Jun 30, 2025 at 2:15 AM Yang Li <yang.li@...ogic.com> wrote:
>
> Hi,
> > [ EXTERNAL EMAIL ]
> >
> > Hi,
> >
> > On Fri, Jun 27, 2025 at 7:31 AM Yang Li <yang.li@...ogic.com> wrote:
> >> 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.
> > What is the backtrace?
> >
> >> 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;
> > It needs to be passed as an argument not just change the role
> > internally otherwise it will break the existing users of it.
>
> After testing, I found that the dst addr of the two BIS connections
> under BIG sync is the address of the BIS source, so I added separate
> checks for MASTER and SLAVE roles.
>
> [ 268.202466][1 T1962 d.] lookup big: 00000000736585c7, addr
> 21:97:07:b1:9f:66, type 131, handle 0x0100, state 1, role 1
> [ 268.203806][1 T1962 d.] lookup big: 0000000041894659, addr
> 21:97:07:b1:9f:66, type 131, handle 0x0101, state 1, role 1
>
> I updated as below,
>
> -hci_conn_hash_lookup_big_state(struct hci_dev *hdev, __u8 handle,
> __u16 state)
> +hci_conn_hash_lookup_big_state(struct hci_dev *hdev, __u8 handle,
> + __u16 state, __u8 role)
> {
> struct hci_conn_hash *h = &hdev->conn_hash;
> struct hci_conn *c;
> @@ -1335,10 +1336,18 @@ hci_conn_hash_lookup_big_state(struct hci_dev
> *hdev, __u8 handle, __u16 state)
> rcu_read_lock();
>
> 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;
> + if (role == HCI_ROLE_MASTER) {
> + if (c->type != BIS_LINK || bacmp(&c->dst,
> BDADDR_ANY) ||
> + c->state != state || c->role != role)
> + continue;
> + } else {
> + if (c->type != BIS_LINK ||
> + c->state != state ||
> + c->role != role)
> + 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).
> > Hmm, that doesn't sound right, if the BIG Sync has been completed the
> > BIS connection shall be moved to BT_CONNECTED. Looks like we are not
> > marking it as connected:
> >
> > hci_le_big_sync_established_evt (Broadcast Sink):
> >
> > set_bit(HCI_CONN_BIG_SYNC, &bis->flags);
> > hci_iso_setup_path(bis);
> >
> > hci_le_create_big_complete_evt (Broadcast Source):
> >
> > conn->state = BT_CONNECTED;
> > set_bit(HCI_CONN_BIG_CREATED, &conn->flags);
> > hci_debugfs_create_conn(conn);
> > hci_conn_add_sysfs(conn);
> > hci_iso_setup_path(conn);
>
> Yes, in addition, state = BT_CONNECTED also needs to be set in
> hci_cc_le_setup_iso_path.
>
> I will update the patch again.
>
> @@ -3890,7 +3890,7 @@ static u8 hci_cc_le_setup_iso_path(struct hci_dev
> *hdev, void *data,
> hci_conn_del(conn);
> goto unlock;
> }
> -
> + conn->state = BT_CONNECTED;
Ive submitted a fix addressing this already:
https://patchwork.kernel.org/project/bluetooth/patch/20250627151902.421666-1-luiz.dentz@gmail.com/
> >> [ 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
> >
> >
> > --
> > Luiz Augusto von Dentz
--
Luiz Augusto von Dentz
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