[PATCH 1/8] UML - watchdog driver locking

From: Jeff Dike
Date: Mon Jan 01 2007 - 14:54:07 EST


Replace BKL use with a spinlock.

Also fix the control so that open doesn't return holding a lock.

Signed-off-by: Jeff Dike <jdike@xxxxxxxxxxx>
--
arch/um/drivers/harddog_kern.c | 23 +++++++++++++++--------
1 file changed, 15 insertions(+), 8 deletions(-)

Index: linux-2.6.18-mm/arch/um/drivers/harddog_kern.c
===================================================================
--- linux-2.6.18-mm.orig/arch/um/drivers/harddog_kern.c 2006-12-29 18:25:36.000000000 -0500
+++ linux-2.6.18-mm/arch/um/drivers/harddog_kern.c 2006-12-29 21:02:50.000000000 -0500
@@ -44,12 +44,13 @@
#include <linux/reboot.h>
#include <linux/smp_lock.h>
#include <linux/init.h>
+#include <linux/spinlock.h>
#include <asm/uaccess.h>
#include "mconsole.h"

MODULE_LICENSE("GPL");

-/* Locked by the BKL in harddog_open and harddog_release */
+static DEFINE_SPINLOCK(lock);
static int timer_alive;
static int harddog_in_fd = -1;
static int harddog_out_fd = -1;
@@ -62,12 +63,12 @@ extern int start_watchdog(int *in_fd_ret

static int harddog_open(struct inode *inode, struct file *file)
{
- int err;
+ int err = -EBUSY;
char *sock = NULL;

- lock_kernel();
+ spin_lock(&lock);
if(timer_alive)
- return -EBUSY;
+ goto err;
#ifdef CONFIG_HARDDOG_NOWAYOUT
__module_get(THIS_MODULE);
#endif
@@ -76,11 +77,15 @@ static int harddog_open(struct inode *in
sock = mconsole_notify_socket();
#endif
err = start_watchdog(&harddog_in_fd, &harddog_out_fd, sock);
- if(err) return(err);
+ if(err)
+ goto err;

timer_alive = 1;
- unlock_kernel();
+ spin_unlock(&lock);
return nonseekable_open(inode, file);
+err:
+ spin_unlock(&lock);
+ return err;
}

extern void stop_watchdog(int in_fd, int out_fd);
@@ -90,14 +95,16 @@ static int harddog_release(struct inode
/*
* Shut off the timer.
*/
- lock_kernel();
+
+ spin_lock(&lock);

stop_watchdog(harddog_in_fd, harddog_out_fd);
harddog_in_fd = -1;
harddog_out_fd = -1;

timer_alive=0;
- unlock_kernel();
+ spin_unlock(&lock);
+
return 0;
}


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