linux-kernel - Re: Linux 3.1-rc9

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Date:	Wed, 2 Nov 2011 19:00:10 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Simon Kirby <sim@...tway.ca>
Cc:	Thomas Gleixner <tglx@...utronix.de>,
	David Miller <davem@...emloft.net>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Dave Jones <davej@...hat.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Network Development <netdev@...r.kernel.org>
Subject: Re: Linux 3.1-rc9

On Wed, Nov 02, 2011 at 06:10:23PM -0400, Steven Rostedt wrote:
> Thomas pointed me here.
> 
> On Mon, Oct 31, 2011 at 10:32:46AM -0700, Simon Kirby wrote:
> > [104661.244767] 
> > [104661.244767]  Possible unsafe locking scenario:
> > [104661.244767]        
> > [104661.244767]        CPU0                    CPU1
> > [104661.244767]        ----                    ----
> > [104661.244767]   lock(slock-AF_INET);
> > [104661.244767]                                lock(slock-AF_INET);
> > [104661.244767]                                lock(slock-AF_INET);
> > [104661.244767]   lock(slock-AF_INET);
> > [104661.244767] 
> > [104661.244767]  *** DEADLOCK ***
> > [104661.244767] 
> 
> Bah, I used the __print_lock_name() function to show the lock names in
> the above, which leaves off the subclass number. I'll go write up a
> patch that fixes that.
> 

Simon,

If you are still triggering the bug. Could you do me a favor and apply
the following patch. Just to make sure it fixes the confusing output
from above.

Thanks,

-- Steve


diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index 91d67ce..d821ac9 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -490,16 +490,22 @@ void get_usage_chars(struct lock_class *class, char usage[LOCK_USAGE_CHARS])
 	usage[i] = '\0';
 }
 
-static int __print_lock_name(struct lock_class *class)
+static void __print_lock_name(struct lock_class *class)
 {
 	char str[KSYM_NAME_LEN];
 	const char *name;
 
 	name = class->name;
-	if (!name)
+	if (!name) {
 		name = __get_key_name(class->key, str);
-
-	return printk("%s", name);
+		printk("%s", name);
+	} else {
+		printk("%s", name);
+		if (class->name_version > 1)
+			printk("#%d", class->name_version);
+		if (class->subclass)
+			printk("/%d", class->subclass);
+	}
 }
 
 static void print_lock_name(struct lock_class *class)
@@ -509,17 +515,8 @@ static void print_lock_name(struct lock_class *class)
 
 	get_usage_chars(class, usage);
 
-	name = class->name;
-	if (!name) {
-		name = __get_key_name(class->key, str);
-		printk(" (%s", name);
-	} else {
-		printk(" (%s", name);
-		if (class->name_version > 1)
-			printk("#%d", class->name_version);
-		if (class->subclass)
-			printk("/%d", class->subclass);
-	}
+	printk(" (");
+	__print_lock_name(class);
 	printk("){%s}", usage);
 }
 
--
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