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 <[email protected]> Cc: Johan Hedberg <[email protected]> Fixes: 38ceaa00d02d ("Bluetooth: Add support for sending MGMT commands and events to monitor") Reported-by: Mart van de Wege <[email protected]> Signed-off-by: Sebastian Andrzej Siewior <[email protected]> --- 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); } -- 2.14.1
