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| author | Shinya Kuribayashi <shinya.kuribayashi.px@renesas.com> | 2012-11-16 01:54:49 (GMT) |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-11-16 02:02:51 (GMT) |
| commit | 33b48e1633f738c5ae78234c2dd5e3a9ba115437 (patch) | |
| tree | 09193c93ad60bdd24e34e382439baa129e2aa02b /drivers/tty | |
| parent | 40f70c03e33a1eed3f3fcd13418e76abad77d117 (diff) | |
| download | linux-33b48e1633f738c5ae78234c2dd5e3a9ba115437.tar.xz | |
serial: sh-sci: fix possible race cases on SCSCR register accesses
In the previous commit, console write function (serial_console_write)
is changed to disable SCI interrupts while printing console strings.
This introduces possible race cases in the serial startup / shutdown
functions on SMP systems.
This patch fixes the sh-sci in the same way as commit 9ec1882df2
(tty: serial: imx: console write routing is unsafe on SMP, from
Xinyu Chen <xinyu.chen@freescale.com>, 2012-08-27) did.
There could be several consumers of the console,
* the kernel printk
* the init process using /dev/kmsg to call printk to show log
* shell, which opens /dev/console and writes with sys_write()
The shell goes into the normal UART open() and write() system calls,
while the other two go into the console operations. The open() call
invokes serial startup function (sci_startup), which will write to
the SCSCR register (to enable or disable SCI interrupts) without any
locking. This will conflict with the console serial function.
Add spinlock protections in sci_startup() and sci_shutdown() properly.
Signed-off-by: Shinya Kuribayashi <shinya.kuribayashi.px@renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/tty')
| -rw-r--r-- | drivers/tty/serial/sh-sci.c | 6 |
1 files changed, 6 insertions, 0 deletions
diff --git a/drivers/tty/serial/sh-sci.c b/drivers/tty/serial/sh-sci.c index 63a23ea..d38c0f5 100644 --- a/drivers/tty/serial/sh-sci.c +++ b/drivers/tty/serial/sh-sci.c @@ -1743,6 +1743,7 @@ static inline void sci_free_dma(struct uart_port *port) static int sci_startup(struct uart_port *port) { struct sci_port *s = to_sci_port(port); + unsigned long flags; int ret; dev_dbg(port->dev, "%s(%d)\n", __func__, port->line); @@ -1753,8 +1754,10 @@ static int sci_startup(struct uart_port *port) sci_request_dma(port); + spin_lock_irqsave(&port->lock, flags); sci_start_tx(port); sci_start_rx(port); + spin_unlock_irqrestore(&port->lock, flags); return 0; } @@ -1762,11 +1765,14 @@ static int sci_startup(struct uart_port *port) static void sci_shutdown(struct uart_port *port) { struct sci_port *s = to_sci_port(port); + unsigned long flags; dev_dbg(port->dev, "%s(%d)\n", __func__, port->line); + spin_lock_irqsave(&port->lock, flags); sci_stop_rx(port); sci_stop_tx(port); + spin_unlock_irqrestore(&port->lock, flags); sci_free_dma(port); sci_free_irq(s); |