Confirm that 4.11.12-rt14 with this fix boots normally.
On Thu, 21 Sep 2017 15:51:23 +0200
Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx> wrote:
> Mart reported a deadlock in -RT in the call path:
> hci_send_monitor_ctrl_event() -> hci_send_to_channel()
>
> because both functions acquire the same read lock hci_sk_list.lock.
> This is also a mainline issue because the qrwlock implementation is
> writer fair (the traditional rwlock implementation is reader biased).
>
> To avoid the deadlock there is now __hci_send_to_channel() which
> expects the readlock to be held.
>
> Cc: Marcel Holtmann <marcel@xxxxxxxxxxxx>
> Cc: Johan Hedberg <johan.hedberg@xxxxxxxxx>
> Fixes: 38ceaa00d02d ("Bluetooth: Add support for sending MGMT
> commands and events to monitor") Reported-by: Mart van de Wege
> <mvdwege@xxxxxxxxx> Signed-off-by: Sebastian Andrzej Siewior
> <bigeasy@xxxxxxxxxxxxx> ---
> net/bluetooth/hci_sock.c | 17 +++++++++++------
> 1 file changed, 11 insertions(+), 6 deletions(-)
>
> diff --git a/net/bluetooth/hci_sock.c b/net/bluetooth/hci_sock.c
> index 638bf0e1a2e3..f1ee820d871c 100644
> --- a/net/bluetooth/hci_sock.c
> +++ b/net/bluetooth/hci_sock.c
> @@ -251,15 +251,13 @@ void hci_send_to_sock(struct hci_dev *hdev,
> struct sk_buff *skb) }
>
> /* Send frame to sockets with specific channel */
> -void hci_send_to_channel(unsigned short channel, struct sk_buff *skb,
> - int flag, struct sock *skip_sk)
> +static void __hci_send_to_channel(unsigned short channel, struct
> sk_buff *skb,
> + int flag, struct sock *skip_sk)
> {
> struct sock *sk;
>
> BT_DBG("channel %u len %d", channel, skb->len);
>
> - read_lock(&hci_sk_list.lock);
> -
> sk_for_each(sk, &hci_sk_list.head) {
> struct sk_buff *nskb;
>
> @@ -285,6 +283,13 @@ void hci_send_to_channel(unsigned short channel,
> struct sk_buff *skb, kfree_skb(nskb);
> }
>
> +}
> +
> +void hci_send_to_channel(unsigned short channel, struct sk_buff *skb,
> + int flag, struct sock *skip_sk)
> +{
> + read_lock(&hci_sk_list.lock);
> + __hci_send_to_channel(channel, skb, flag, skip_sk);
> read_unlock(&hci_sk_list.lock);
> }
>
> @@ -388,8 +393,8 @@ void hci_send_monitor_ctrl_event(struct hci_dev
> *hdev, u16 event, hdr->index = index;
> hdr->len = cpu_to_le16(skb->len - HCI_MON_HDR_SIZE);
>
> - hci_send_to_channel(HCI_CHANNEL_MONITOR, skb,
> - HCI_SOCK_TRUSTED, NULL);
> + __hci_send_to_channel(HCI_CHANNEL_MONITOR, skb,
> + HCI_SOCK_TRUSTED, NULL);
> kfree_skb(skb);
> }
>
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