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From: Alan Cox on 5 May 2010 06:50
The riscom8 board uses lock_kernel to protect bits of the port setting
ioctl logic. We can use the port mutex for this as the logic is internal
and will also lock set versus open (a locking property that has been lost
somewhere along the way)

Signed-off-by: Alan Cox <alan(a)linux.intel.com>
---

drivers/char/riscom8.c | 14 ++++++++------
1 files changed, 8 insertions(+), 6 deletions(-)


diff --git a/drivers/char/riscom8.c b/drivers/char/riscom8.c
index b02332a..af4de1f 100644
--- a/drivers/char/riscom8.c
+++ b/drivers/char/riscom8.c
@@ -47,7 +47,6 @@
#include <linux/init.h>
#include <linux/delay.h>
#include <linux/tty_flip.h>
-#include <linux/smp_lock.h>
#include <linux/spinlock.h>
#include <linux/device.h>

@@ -1184,6 +1183,7 @@ static int rc_set_serial_info(struct tty_struct *tty, struct riscom_port *port,
if (copy_from_user(&tmp, newinfo, sizeof(tmp)))
return -EFAULT;

+ mutex_lock(&port->port.mutex);
change_speed = ((port->port.flags & ASYNC_SPD_MASK) !=
(tmp.flags & ASYNC_SPD_MASK));

@@ -1191,8 +1191,10 @@ static int rc_set_serial_info(struct tty_struct *tty, struct riscom_port *port,
if ((tmp.close_delay != port->port.close_delay) ||
(tmp.closing_wait != port->port.closing_wait) ||
((tmp.flags & ~ASYNC_USR_MASK) !=
- (port->port.flags & ~ASYNC_USR_MASK)))
+ (port->port.flags & ~ASYNC_USR_MASK))) {
+ mutex_unlock(&port->port.mutex);
return -EPERM;
+ }
port->port.flags = ((port->port.flags & ~ASYNC_USR_MASK) |
(tmp.flags & ASYNC_USR_MASK));
} else {
@@ -1208,6 +1210,7 @@ static int rc_set_serial_info(struct tty_struct *tty, struct riscom_port *port,
rc_change_speed(tty, bp, port);
spin_unlock_irqrestore(&riscom_lock, flags);
}
+ mutex_unlock(&port->port.mutex);
return 0;
}

@@ -1220,12 +1223,15 @@ static int rc_get_serial_info(struct riscom_port *port,
memset(&tmp, 0, sizeof(tmp));
tmp.type = PORT_CIRRUS;
tmp.line = port - rc_port;
+
+ mutex_lock(&port->port.mutex);
tmp.port = bp->base;
tmp.irq = bp->irq;
tmp.flags = port->port.flags;
tmp.baud_base = (RC_OSCFREQ + CD180_TPC/2) / CD180_TPC;
tmp.close_delay = port->port.close_delay * HZ/100;
tmp.closing_wait = port->port.closing_wait * HZ/100;
+ mutex_unlock(&port->port.mutex);
tmp.xmit_fifo_size = CD180_NFIFO;
return copy_to_user(retinfo, &tmp, sizeof(tmp)) ? -EFAULT : 0;
}
@@ -1242,14 +1248,10 @@ static int rc_ioctl(struct tty_struct *tty, struct file *filp,

switch (cmd) {
case TIOCGSERIAL:
- lock_kernel();
retval = rc_get_serial_info(port, argp);
- unlock_kernel();
break;
case TIOCSSERIAL:
- lock_kernel();
retval = rc_set_serial_info(tty, port, argp);
- unlock_kernel();
break;
default:
retval = -ENOIOCTLCMD;

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Prev: [PATCH 19/20] serial: trim locking on the helpers
Next: [PATCH 08/20] epca: Kill the big kernel lock