linux-kernel - Re: [PATCH] USB: move usb debugfs directory creation to the usb common core

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Date:   Tue, 4 Jun 2019 14:43:49 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Felipe Balbi <felipe.balbi@...ux.intel.com>
Cc:     Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH] USB: move usb debugfs directory creation to the usb
 common core

On Tue, Jun 04, 2019 at 03:25:14PM +0300, Felipe Balbi wrote:
> 
> Hi,
> 
> Greg Kroah-Hartman <gregkh@...uxfoundation.org> writes:
> > diff --git a/drivers/usb/core/usb.c b/drivers/usb/core/usb.c
> > index 7fcb9f782931..f3d6b1ab80cb 100644
> > --- a/drivers/usb/core/usb.c
> > +++ b/drivers/usb/core/usb.c
> > @@ -1185,19 +1185,17 @@ static struct notifier_block usb_bus_nb = {
> >  	.notifier_call = usb_bus_notify,
> >  };
> >  
> > -struct dentry *usb_debug_root;
> > -EXPORT_SYMBOL_GPL(usb_debug_root);
> > +static struct dentry *usb_devices_root;
> >  
> >  static void usb_debugfs_init(void)
> >  {
> > -	usb_debug_root = debugfs_create_dir("usb", NULL);
> > -	debugfs_create_file("devices", 0444, usb_debug_root, NULL,
> > -			    &usbfs_devices_fops);
> > +	usb_devices_root = debugfs_create_file("devices", 0444, usb_debug_root,
> 
> don't we have a race now? Can usbcore ever probe before usb common?

How can that happen if usb_debug_root is in usb common?  The module
loader will not let that happen.  Or it shouldn't :)

thanks,

greg k-h