linux-kernel - Re: [patch 02/10] Linux Kernel Markers, architecture independent code.

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Date:	Thu, 10 May 2007 23:00:27 +0400
From:	Alexey Dobriyan <adobriyan@...il.com>
To:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
Cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	hch@...radead.org, Adrian Bunk <bunk@...sta.de>
Subject: Re: [patch 02/10] Linux Kernel Markers, architecture independent code.

On Thu, May 10, 2007 at 09:12:41AM -0400, Mathieu Desnoyers wrote:
> Linux Kernel Markers - Architecture Independant Code fix 2
>
> Fix trivial SMP bug in list_modules.

> --- linux-2.6-lttng.orig/kernel/module.c	2007-05-10 08:51:02.000000000 -0400
> +++ linux-2.6-lttng/kernel/module.c	2007-05-10 08:51:06.000000000 -0400
> @@ -2657,13 +2657,16 @@
>  	/* Enumerate loaded modules */
>  	struct list_head	*i;
>  	struct module		*mod;
> -	unsigned long refcount = 0;
> +	unsigned long refcount;
> +	int cpu;
>
>  	mutex_lock(&module_mutex);
>  	list_for_each(i, &modules) {
>  		mod = list_entry(i, struct module, list);
> +		refcount = 0;
>  #ifdef CONFIG_MODULE_UNLOAD
> -		refcount = local_read(&mod->ref[0].count);
> +		for_each_online_cpu(cpu)
> +			refcount += local_read(&mod->ref[cpu].count);
>  #endif //CONFIG_MODULE_UNLOAD

Still wrong: module_get on cpu X, cpu X hot unplugged. There is
module_refcount() for you.

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