[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>

1 files changed, 27 insertions, 3 deletions

diff --git a/drivers/watchdog/wdt.c b/drivers/watchdog/wdt.c
index 53d0bb410df8..756fb15fdce7 100644
--- 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;
 }