msm: ipc: Fix potential AB-BA deadlock
In kernel QMI, while receiving responses continuously, there is a
classic out-of-order(AB-BA) deadlock scenario between IPC router and
Kernel QMI interface. The scenario is as below:
1) IPC Router receives the message for kernel QMI port and acquires the
corresponding port's port_rx_q_lock and then calls the notify
function for that port which tries to acquire the handle_lock of the
port.
2) Kernel QMI interface, that runs independent of IPC Router activities,
tries to send a message and acquires handle_lock for the port and
tries to acquire the port's port_rx_q_lock to read the response from
the port.
3) This creates a classic AB-BA deadlock because port_rx_q_lock is
locked at step 1 and handle_lock is acquired at step 2.
Fix the deadlock.
Change-Id: I532cff30b445e11baa715a570e5e853d9b71bab3
Signed-off-by: Zaheerulla Meer <zmeer@codeaurora.org>
1 file changed