Re: discriminate single bit error hardware failure from slab corruption.

[Dave Jones <davej@redhat.com>]

On Thu, Feb 02, 2006 at 08:41:26PM -0800, Roland Dreier wrote:
 >     Dave> Hmm, I made a mistake in my maths somewhere, and some of
 >     Dave> those values are incorrect, so having the compiler do the
 >     Dave> work would have stopped me screwing up, but once the correct
 >     Dave> values are used, I doubt there's ever a really compelling
 >     Dave> reason to change the slab poison pattern.
 > 
 > But Avi is still correct about false positives.  For example, if
 > something stomps on the slab poison and leaves it as
 > 
 >     e0 08 03 00
 > 
 > then that will add up to eb and still trigger your message, even
 > though it's far from a single bit error.

Ah, now I see the point Avi was making.

 > Maybe making the loop be something like
 > 
 > 	unsigned char total = 0, bad_count = 0;
 > 	printk(KERN_ERR "%03x:", offset);
 > 	for (i = 0; i < limit; i++) {
 > 		if (data[offset+i] != POISON_FREE) {
 > 			total += data[offset+i];
 > 			++bad_count;
 > 		}
 > 		printk(" %02x", (unsigned char)data[offset + i]);
 > 	}
 > 
 > and then you can put
 > 
 > 	if (bad_count == 1)
 > 
 > before the switch statement.
 > 
 > I have to admit that Avi's code seems clearer to me too, though.

I'm easily persuaded either way really, as long as
we arrive at a desirable end-result ;)

		Dave