linux-kernel - Re: [Pv-drivers] [PATCH 08/12] VMCI: resource object implementation.

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Date:	Mon, 29 Oct 2012 22:20:16 -0700
From:	Dmitry Torokhov <dtor@...are.com>
To:	Greg KH <gregkh@...uxfoundation.org>
Cc:	George Zhang <georgezhang@...are.com>, pv-drivers@...are.com,
	linux-kernel@...r.kernel.org,
	virtualization@...ts.linux-foundation.org
Subject: Re: [Pv-drivers] [PATCH 08/12] VMCI: resource object implementation.

On Mon, Oct 29, 2012 at 07:29:05PM -0700, Greg KH wrote:
> On Mon, Oct 29, 2012 at 06:04:58PM -0700, George Zhang wrote:
> > +static struct vmci_resource *vmci_resource_lookup(struct vmci_handle handle)
> > +{
> > +	struct vmci_resource *r, *resource = NULL;
> > +	struct hlist_node *node;
> > +	unsigned int idx = vmci_resource_hash(handle);
> > +
> > +	BUG_ON(VMCI_HANDLE_EQUAL(handle, VMCI_INVALID_HANDLE));
> 
> You just crashed a machine, with no chance for recovery.  Not a good
> idea.  Never a good idea.  Customers just lost data, and now they are
> mad.  Make sure you at least print out your email address so they know
> who to blame :)
> 
> Seriously, never BUG() in a driver, warn, sure, but this just looks like
> a debugging assert().  Please remove all of these, they are sprinkled
> all over the driver code here, I'm only responding to one of them here.
> 
> Even better yet, properly handle the error and keep on going, that's
> what the rest of the kernel does.  Or should :)

For public APIs it certainly makes sense to check and handle erroneous input;
internally it often makes sense to simply enforce invariants, because if
we managed to get into that state that we consider impossible we can't really
trust anything.

FWIW:
[dtor@...r-ws kernel]$ grep -r BUG_ON . | wc -l
11269

Thanks,
Dmitry


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