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Commit 2f65d957 authored by Luke Zhang's avatar Luke Zhang Committed by Hemant Gupta
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Prevent deadlock between the Tx and Rx threads in HCI layer 

Problem: Deadlock between HCI layer's Tx and Rx threads.

Cause: In HCI layer, both Tx and Rx tried to acquire
commands_pending_response_mutex simultaneously.
Since there may be a handshake between Tx and Rx
in the BT Transport layer, so it caused a deadlock between
HCI layer's Tx and Rx threads.

Fix: Fixed it by decreasing the scope of this mutex in Tx thread

Test: Simulated the deadlock sitaution and ensured RX thread is returned when TX is busy in binder.

Bug: 68305277
Change-Id: I0a2434ec24918b039a6993d57e68ac7495e31cbe
parent 88258d17

system/hci/src/hci_layer.cc

+6 −5
Original line number Original line Diff line number Diff line
@@ -394,11 +394,12 @@ static void enqueue_command(waiting_command_t* wait_entry) { 
}

}





static void event_command_ready(waiting_command_t* wait_entry) {

static void event_command_ready(waiting_command_t* wait_entry) {

  {

    /// Move it to the list of commands awaiting response

    /// Move it to the list of commands awaiting response

    std::lock_guard<std::recursive_mutex> lock(commands_pending_response_mutex);

    std::lock_guard<std::recursive_mutex> lock(commands_pending_response_mutex);

    wait_entry->timestamp = std::chrono::steady_clock::now();

    wait_entry->timestamp = std::chrono::steady_clock::now();

    list_append(commands_pending_response, wait_entry);

    list_append(commands_pending_response, wait_entry);



  }

  // Send it off

  // Send it off

  packet_fragmenter->fragment_and_dispatch(wait_entry->command);

  packet_fragmenter->fragment_and_dispatch(wait_entry->command);