Re : 16 potential locking bugs in 2.4.1 (wavelan patch attached)

[Jean Tourrilhes <jt@bougret.hpl.hp.com>]

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Andy Chou :
> Here are some more results from the MC project. These are 16 errors found 
> in 2.4.1 related to inconsistent use of locks. As usual, if you can 
> verify any of these or show that they are false positives, please let us 
> know by CC'ing mc@cs.stanford.edu. 
> 
> -Andy Chou 
>
> -----------------------------------------------------------------------------
> 
> [BUG] error condition 
> /u2/acc/oses/linux/2.4.1/drivers/net/pcmcia/wavelan_cs.c:2561:wavelan_get_wireless_stats:
> ERROR:LOCK:2528:2561: Inconsistent 
> lock using `spin_lock':2528 
> 
> static iw_stats * 
> wavelan_get_wireless_stats(device * dev) 
> { 
>   ... 
> --> Lock 
>   spin_lock_irqsave (&lp->lock, flags); 
> 
>   if(lp == (net_local *) NULL) 
> --> Missing unlock? 
>     return (iw_stats *) NULL; 
> 
> -----------------------------------------------------------------------------

	Thanks for the hint (actually, also thanks to LWN for
reporting this, I don't read the list).
	At first, I felt offended to have such an obvious bug in my
driver, and then I check the master copy of the driver in the Pcmcia
package that I maintain, and it doesn't contain this bug. So whoever
did the port from Pcmcia -> kernel introduced this one :-(
	Patch attached. Have fun...

	Jean


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diff -u -p linux/drivers/net/pcmcia/wireless.24d/wavelan_cs.c linux/drivers/net/pcmcia/wavelan_cs.c
--- linux/drivers/net/pcmcia/wireless.24d/wavelan_cs.c	Thu Mar 22 15:08:46 2001
+++ linux/drivers/net/pcmcia/wavelan_cs.c	Thu Mar 22 15:10:25 2001
@@ -2524,11 +2524,13 @@ wavelan_get_wireless_stats(device *	dev)
   printk(KERN_DEBUG "%s: ->wavelan_get_wireless_stats()\n", dev->name);
 #endif
 
+  /* Pure paranoia */
+  if(lp == (net_local *) NULL)
+    return (iw_stats *) NULL;
+
   /* Disable interrupts & save flags */
   spin_lock_irqsave (&lp->lock, flags);
 
-  if(lp == (net_local *) NULL)
-    return (iw_stats *) NULL;
   wstats = &lp->wstats;
 
   /* Get data from the mmc */