@@ -605,9 +605,13 @@ static int brcmuart_startup(struct uart_port *port)
/*
* Disable the Receive Data Interrupt because the DMA engine
* will handle this.
+ *
+ * Synchronize UART_IER access against the console.
*/
+ spin_lock_irq(&port->lock);
up->ier &= ~UART_IER_RDI;
serial_port_out(port, UART_IER, up->ier);
+ spin_unlock_irq(&port->lock);
priv->tx_running = false;
priv->dma.rx_dma = NULL;
@@ -194,8 +194,12 @@ static int xr17v35x_startup(struct uart_port *port)
/*
* Make sure all interrups are masked until initialization is
* complete and the FIFOs are cleared
+ *
+ * Synchronize UART_IER access against the console.
*/
+ spin_lock_irq(&port->lock);
serial_port_out(port, UART_IER, 0);
+ spin_unlock_irq(&port->lock);
return serial8250_do_startup(port);
}
@@ -710,8 +710,11 @@ static int omap_8250_startup(struct uart_port *port)
up->dma = NULL;
}
+ /* Synchronize UART_IER access against the console. */
+ spin_lock_irq(&port->lock);
up->ier = UART_IER_RLSI | UART_IER_RDI;
serial_out(up, UART_IER, up->ier);
+ spin_unlock_irq(&port->lock);
#ifdef CONFIG_PM
up->capabilities |= UART_CAP_RPM;
@@ -2149,7 +2149,12 @@ int serial8250_do_startup(struct uart_port *port)
serial8250_rpm_get(up);
if (port->type == PORT_16C950) {
- /* Wake up and initialize UART */
+ /*
+ * Wake up and initialize UART
+ *
+ * Synchronize UART_IER access against the console.
+ */
+ spin_lock_irqsave(&port->lock, flags);
up->acr = 0;
serial_port_out(port, UART_LCR, UART_LCR_CONF_MODE_B);
serial_port_out(port, UART_EFR, UART_EFR_ECB);
@@ -2159,12 +2164,19 @@ int serial8250_do_startup(struct uart_port *port)
serial_port_out(port, UART_LCR, UART_LCR_CONF_MODE_B);
serial_port_out(port, UART_EFR, UART_EFR_ECB);
serial_port_out(port, UART_LCR, 0);
+ spin_unlock_irqrestore(&port->lock, flags);
}
if (port->type == PORT_DA830) {
- /* Reset the port */
+ /*
+ * Reset the port
+ *
+ * Synchronize UART_IER access against the console.
+ */
+ spin_lock_irqsave(&port->lock, flags);
serial_port_out(port, UART_IER, 0);
serial_port_out(port, UART_DA830_PWREMU_MGMT, 0);
+ spin_unlock_irqrestore(&port->lock, flags);
mdelay(10);
/* Enable Tx, Rx and free run mode */
@@ -2275,6 +2287,8 @@ int serial8250_do_startup(struct uart_port *port)
* this interrupt whenever the transmitter is idle and
* the interrupt is enabled. Delays are necessary to
* allow register changes to become visible.
+ *
+ * Synchronize UART_IER access against the console.
*/
spin_lock_irqsave(&port->lock, flags);
uart_ops startup() callback is called without interrupts disabled and without port->lock locked, relatively late during the boot process (from the call path of console_on_rootfs()). If the device is a console, it was already previously registered and could be actively printing messages. The console printing function serial8250_console_write() modifies the interrupt register (UART_IER) under the port->lock with the pattern: read, clear, restore. Since some startup() callbacks are modifying UART_IER without the port->lock locked, it is possible that the value intended to be written by the startup() callback will get overwritten and be lost. CPU0 CPU1 serial8250_console_write omap_8250_startup -------------------------- ----------------- spin_lock(port->lock) oldval = read(UART_IER) uart_console_write() write(newval, UART_IER) write(oldval, UART_IER) spin_unlock(port->lock) Add port->lock synchronization to the 8250 startup() callbacks where they need to access UART_IER. This avoids racing with serial8250_console_write(). Signed-off-by: John Ogness <john.ogness@linutronix.de> --- drivers/tty/serial/8250/8250_bcm7271.c | 4 ++++ drivers/tty/serial/8250/8250_exar.c | 4 ++++ drivers/tty/serial/8250/8250_omap.c | 3 +++ drivers/tty/serial/8250/8250_port.c | 18 ++++++++++++++++-- 4 files changed, 27 insertions(+), 2 deletions(-)