linux-kernel - Re: [PATCH] block2mtd lockdep_init

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Date:	Mon, 07 Jan 2008 11:05:26 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Erez Zadok <ezk@...sunysb.edu>
Cc:	Jörn Engel <joern@...fs.org>,
	dwmw2@...radead.org, linux-mtd@...ts.infradead.org,
	mingo@...hat.com, linux-kernel@...r.kernel.org,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [PATCH] block2mtd lockdep_init_map warning


On Sun, 2008-01-06 at 14:11 -0500, Erez Zadok wrote:

> > Ingo, Peter, does either of you actually care about this problem?  In
> > the last round when I debugged this problem there was a notable lack of
> > reaction from either of you.
> 
> The problem appears to be an interaction of two components--module loading
> and lockdep--that's perhaps why it wasn't given enough attention.

Would something like this work for people?

Not-Yet-Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
---
Index: linux-2.6/include/linux/sched.h
===================================================================
--- linux-2.6.orig/include/linux/sched.h
+++ linux-2.6/include/linux/sched.h
@@ -1160,6 +1160,7 @@ struct task_struct {
 	int lockdep_depth;
 	struct held_lock held_locks[MAX_LOCK_DEPTH];
 	unsigned int lockdep_recursion;
+	struct module *loading_module;
 #endif
 
 /* journalling filesystem info */
Index: linux-2.6/kernel/module.c
===================================================================
--- linux-2.6.orig/kernel/module.c
+++ linux-2.6/kernel/module.c
@@ -2023,6 +2023,9 @@ static struct module *load_module(void _
 		printk(KERN_WARNING "%s: Ignoring obsolete parameters\n",
 		       mod->name);
 
+#ifdef CONFIG_LOCKDEP
+	current->loading_module = mod;
+#endif
 	/* Size of section 0 is 0, so this works well if no params */
 	err = parse_args(mod->name, mod->args,
 			 (struct kernel_param *)
@@ -2030,6 +2033,9 @@ static struct module *load_module(void _
 			 sechdrs[setupindex].sh_size
 			 / sizeof(struct kernel_param),
 			 NULL);
+#ifdef CONFIG_LOCKDEP
+	current->loading_module = NULL
+#endif
 	if (err < 0)
 		goto arch_cleanup;
 
@@ -2454,6 +2460,17 @@ int is_module_address(unsigned long addr
 		}
 	}
 
+#ifdef CONFIG_LOCKDEP
+	if (current->loading_module) {
+		mod = current->loading_module;
+		if (within(addr, mod->module_init, mod->init_text_size)
+		    || within(addr, mod->module_core, mod->core_text_size)) {
+			preempt_enable();
+			return 1;
+		}
+	}
+#endif
+
 	preempt_enable();
 
 	return 0;



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