irda: ali-ircc: Fix deadlock in ali_ircc_sir_change_speed()

ali_ircc_sir_change_speed() is always called with self->lock held,
so acquiring the lock inside it leads to unavoidable deadlock.

Call graph:
ali_ircc_sir_change_speed() is called from ali_ircc_change_speed()
  ali_ircc_fir_hard_xmit() under spin_lock_irqsave(&self->lock, flags);
  ali_ircc_sir_hard_xmit() under spin_lock_irqsave(&self->lock, flags);
  ali_ircc_net_ioctl() under spin_lock_irqsave(&self->lock, flags);
  ali_ircc_dma_xmit_complete()
    ali_ircc_fir_interrupt()
      ali_ircc_interrupt() under spin_lock(&self->lock);
  ali_ircc_sir_write_wakeup()
    ali_ircc_sir_interrupt()
      ali_ircc_interrupt() under spin_lock(&self->lock);

The patch removes spin_lock/unlock from ali_ircc_sir_change_speed().

Found by Linux Driver Verification project (linuxtesting.org).

Signed-off-by: Alexey Khoroshilov <khoroshilov@ispras.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/drivers/net/irda/ali-ircc.c b/drivers/net/irda/ali-ircc.c
index 58ae11a14bb6f9ea51f322faaafee10b357ddddf..64bb44d5d8672a2f078a69074a1c9e6e9d4fda27 100644 (file)
--- a/drivers/net/irda/ali-ircc.c
+++ b/drivers/net/irda/ali-ircc.c
@@ -1031,7 +1031,6 @@ static void ali_ircc_fir_change_speed(struct ali_ircc_cb *priv, __u32 baud)
 static void ali_ircc_sir_change_speed(struct ali_ircc_cb *priv, __u32 speed)
 {
        struct ali_ircc_cb *self = priv;
-       unsigned long flags;
        int iobase; 
        int fcr;    /* FIFO control reg */
        int lcr;    /* Line control reg */
@@ -1061,8 +1060,6 @@ static void ali_ircc_sir_change_speed(struct ali_ircc_cb *priv, __u32 speed)
        /* Update accounting for new speed */
        self->io.speed = speed;
 
-       spin_lock_irqsave(&self->lock, flags);
-
        divisor = 115200/speed;
        
        fcr = UART_FCR_ENABLE_FIFO;
@@ -1089,9 +1086,6 @@ static void ali_ircc_sir_change_speed(struct ali_ircc_cb *priv, __u32 speed)
        /* without this, the connection will be broken after come back from FIR speed,
           but with this, the SIR connection is harder to established */
        outb((UART_MCR_DTR | UART_MCR_RTS | UART_MCR_OUT2), iobase+UART_MCR);
-       
-       spin_unlock_irqrestore(&self->lock, flags);
-       
 }
 
 static void ali_ircc_change_dongle_speed(struct ali_ircc_cb *priv, int speed)