[WATCHDOG] wdt: fix locking

The audit of _p usage shows various drivers assume inb_p is somehow atomic.
 Of course it isn't and the delay can be split from the I/O cycle causing a
timing violation on chips that matter (eg this one)

With the proposed use of udelay() for some _p delays this will cease to be
a mostly theoretical bug (as the delay stall is unsplittable) and wants
fixing.

Lots of other drivers need fixing this way too.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/drivers/watchdog/wdt.c b/drivers/watchdog/wdt.c
index 53d0bb410df8c6811db704e91340ddc134b775d1..756fb15fdce7aa97c1bfebbf0e8fcbf42fb5ee14 100644 (file)
--- a/drivers/watchdog/wdt.c
+++ b/drivers/watchdog/wdt.c
@@ -70,6 +70,8 @@ MODULE_PARM_DESC(nowayout, "Watchdog cannot be stopped once started (default=" _
 static int io=0x240;
 static int irq=11;
 
+static DEFINE_SPINLOCK(wdt_lock);
+
 module_param(io, int, 0);
 MODULE_PARM_DESC(io, "WDT io port (default=0x240)");
 module_param(irq, int, 0);
@@ -109,6 +111,8 @@ static void wdt_ctr_load(int ctr, int val)
 
 static int wdt_start(void)
 {
+       unsigned long flags;
+       spin_lock_irqsave(&wdt_lock, flags);
        inb_p(WDT_DC);                  /* Disable watchdog */
        wdt_ctr_mode(0,3);              /* Program CTR0 for Mode 3: Square Wave Generator */
        wdt_ctr_mode(1,2);              /* Program CTR1 for Mode 2: Rate Generator */
@@ -117,6 +121,7 @@ static int wdt_start(void)
        wdt_ctr_load(1,wd_heartbeat);   /* Heartbeat */
        wdt_ctr_load(2,65535);          /* Length of reset pulse */
        outb_p(0, WDT_DC);              /* Enable watchdog */
+       spin_unlock_irqrestore(&wdt_lock, flags);
        return 0;
 }
 
@@ -128,9 +133,12 @@ static int wdt_start(void)
 
 static int wdt_stop (void)
 {
+       unsigned long flags;
+       spin_lock_irqsave(&wdt_lock, flags);
        /* Turn the card off */
        inb_p(WDT_DC);                  /* Disable watchdog */
        wdt_ctr_load(2,0);              /* 0 length reset pulses now */
+       spin_unlock_irqrestore(&wdt_lock, flags);
        return 0;
 }
 
@@ -143,11 +151,14 @@ static int wdt_stop (void)
 
 static int wdt_ping(void)
 {
+       unsigned long flags;
+       spin_lock_irqsave(&wdt_lock, flags);
        /* Write a watchdog value */
        inb_p(WDT_DC);                  /* Disable watchdog */
        wdt_ctr_mode(1,2);              /* Re-Program CTR1 for Mode 2: Rate Generator */
        wdt_ctr_load(1,wd_heartbeat);   /* Heartbeat */
        outb_p(0, WDT_DC);              /* Enable watchdog */
+       spin_unlock_irqrestore(&wdt_lock, flags);
        return 0;
 }
 
@@ -182,7 +193,12 @@ static int wdt_set_heartbeat(int t)
 
 static int wdt_get_status(int *status)
 {
-       unsigned char new_status=inb_p(WDT_SR);
+       unsigned char new_status;
+       unsigned long flags;
+
+       spin_lock_irqsave(&wdt_lock, flags);
+       new_status = inb_p(WDT_SR);
+       spin_unlock_irqrestore(&wdt_lock, flags);
 
        *status=0;
        if (new_status & WDC_SR_ISOI0)
@@ -214,8 +230,12 @@ static int wdt_get_status(int *status)
 
 static int wdt_get_temperature(int *temperature)
 {
-       unsigned short c=inb_p(WDT_RT);
+       unsigned short c;
+       unsigned long flags;
 
+       spin_lock_irqsave(&wdt_lock, flags);
+       c = inb_p(WDT_RT);
+       spin_unlock_irqrestore(&wdt_lock, flags);
        *temperature = (c * 11 / 15) + 7;
        return 0;
 }
@@ -237,7 +257,10 @@ static irqreturn_t wdt_interrupt(int irq, void *dev_id)
         *      Read the status register see what is up and
         *      then printk it.
         */
-       unsigned char status=inb_p(WDT_SR);
+       unsigned char status;
+
+       spin_lock(&wdt_lock);
+       status = inb_p(WDT_SR);
 
        printk(KERN_CRIT "WDT status %d\n", status);
 
@@ -265,6 +288,7 @@ static irqreturn_t wdt_interrupt(int irq, void *dev_id)
                printk(KERN_CRIT "Reset in 5ms.\n");
 #endif
        }
+       spin_unlock(&wdt_lock);
        return IRQ_HANDLED;
 }