Re: [PATCH 1/1] radix-tree: do not export radix_tree_preloads as GPL

From: Seth Forshee <seth.forshee@canonical.com>
To: Alberto Milone <alberto.milone@canonical.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	linux-fsdevel@vger.kernel.org, mingo@kernel.org
Subject: Re: [PATCH 1/1] radix-tree: do not export radix_tree_preloads as GPL
Date: Fri, 17 Jul 2020 09:28:48 -0500	[thread overview]
Message-ID: <20200717142848.GK3644@ubuntu-x1> (raw)
In-Reply-To: <ea8b14c7-cda9-d0c1-b36a-8f2deea3ca18@canonical.com>

On Fri, Jul 17, 2020 at 03:45:10PM +0200, Alberto Milone wrote:
> On 17/07/2020 15:21, Sebastian Andrzej Siewior wrote:
> > On 2020-07-17 14:33:31 [+0200], Alberto Milone wrote:
> >> I checked and CONFIG_DEBUG_LOCK_ALLOC is not enabled in our kernels.
> > The access to that variable is optimized away if not for debug. I made
> > this:
> > | #include <linux/module.h>
> > | #include <linux/idr.h>
> > | 
> > | static int le_init(void)
> > | {
> > |         idr_preload_end();
> > |         return 0;
> > | }
> > | module_init(le_init);
> > | 
> > | static void le_exit(void)
> > | {
> > | }
> > | module_exit(le_exit);
> > |    
> > | MODULE_DESCRIPTION("driver");
> > | MODULE_LICENSE("prop");
> >
> > and it produced a .ko. Here the "idr_preload_end()" was reduced to
> > "preempt_enable()" as intended. No access to
> > "&radix_tree_preloads.lock".
> >
> > Sebastian
> * Subscribing Seth

Looks like the driver is not using idr_preload_end() though, it is
calling radix_tree_preload_end() which uses radix_tree_preloads whether
or not CONFIG_DEBUG_LOCK_ALLOC is enabled.

Thanks,
Seth