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Date: Fri, 31 Dec 2004 03:42:57 -0800
From: Andrew Morton <akpm@osdl.org>
To: Paulo Marques <pmarques@grupopie.com>
Cc: opengeometry@yahoo.ca, juhl-lkml@dif.dk, marcelo.tosatti@cyclades.com,
       linux-kernel@vger.kernel.org
Subject: Re: waiting 10s before mounting root filesystem?
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Paulo Marques <pmarques@grupopie.com> wrote:
>
> Andrew Morton wrote:
> > William Park <opengeometry@yahoo.ca> wrote:
> > 
> >>-		printk("VFS: Cannot open root device \"%s\" or %s\n",
> >> -				root_device_name, b);
> >> -		printk("Please append a correct \"root=\" boot option\n");
> >> +		if (--tryagain) {
> >> +		    printk (KERN_WARNING "VFS: Waiting %dsec for root device...\n", tryagain);
> >> +		    ssleep (1);
> >> +		    goto retry;
> >> +		}
> >> +		printk (KERN_CRIT "VFS: Cannot open root device \"%s\" or %s\n", root_device_name, b);
> >> +		printk (KERN_CRIT "Please append a correct \"root=\" boot option\n");
> > 
> > 
> > Why is this patch needed?  If it is to offer the user a chance to insert
> > the correct medium or to connect the correct device, why not rely upon the
> > user doing that thing and then hitting reset?
> 
> No, no. The problem is not user interaction.
> 
> The problem is that the USB subsystem takes a lot of time to go through 
> the hostcontrollers -> hubs -> devices. By the time it finds the USB 
> mass storage that is supposed to be used as root filesystem, the kernel 
> had already panic'ed.

That would be a USB bug, surely.  If /dev/usb/foo is present and
functioning correctly, and higher-level code tries to access that device,
USB should _not_ error out - it should block the caller until everything is
sorted out.