linux-kernel - Re: Regression associated with commit c8628155ece3

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Date:	Fri, 24 Aug 2012 09:09:57 -0500
From:	Larry Finger <Larry.Finger@...inger.net>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Neal Cardwell <ncardwell@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	John W Linville <linville@...driver.com>,
	linux-wireless <linux-wireless@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: Regression associated with commit c8628155ece3 - "tcp: reduce
 out_of_order memory use"

On 08/23/2012 04:26 PM, Eric Dumazet wrote:
>
> skb->truesize is adjusted when a frag is added to one skb, or when
> skb->head is re-allocated.
>
> Are you sure you dont have another problem, because as I said commit
> c8628155ece3  had a bug, so a bisect is not very useful.
>
> How many reloads are needed to trigger the bug, do you have a script to
> reproduce it ?

I was doing the tests with a browser; however, it seems that a wget of that same 
page is much more effective at triggering the problem. Now I have a script that 
tries 60 passes of

wget https://bugzilla.redhat.com/show_bug.cgi?id=847525

I usually get failures on the first or second try. A kernel built from "git 
checkout c862815" gets the following wget output:

============================================================================
--2012-08-23 21:50:32--  https://bugzilla.redhat.com/show_bug.cgi?id=847525
Resolving bugzilla.redhat.com (bugzilla.redhat.com)... 209.132.183.69
Connecting to bugzilla.redhat.com (bugzilla.redhat.com)|209.132.183.69|:443... 
connected.
OpenSSL: error:0D0680A8:asn1 encoding routines:ASN1_CHECK_TLEN:wrong tag
OpenSSL: error:0D07803A:asn1 encoding routines:ASN1_ITEM_EX_D2I:nested asn1 error
OpenSSL: error:0D08303A:asn1 encoding routines:ASN1_TEMPLATE_NOEXP_D2I:nested 
asn1 error
OpenSSL: error:0D08303A:asn1 encoding routines:ASN1_TEMPLATE_NOEXP_D2I:nested 
asn1 error
OpenSSL: error:1409000D:SSL routines:SSL3_GET_SERVER_CERTIFICATE:ASN1 lib
Unable to establish SSL connection.
============================================================================

With kernel 3.6-rc2, the error changes to the following:

============================================================================
--2012-08-24 08:26:42--  https://bugzilla.redhat.com/show_bug.cgi?id=847525
Resolving bugzilla.redhat.com (bugzilla.redhat.com)... 209.132.183.69
Connecting to bugzilla.redhat.com (bugzilla.redhat.com)|209.132.183.69|:443... 
connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]
Saving to: `show_bug.cgi?id=847525.3'

     [ <=>                          ] 0           --.-K/s   in 0s

2012-08-24 08:26:45 (0.00 B/s) - Read error at byte 0 (error:1408F119:SSL 
routines:SSL3_GET_RECORD:decryption failed or bad record mac).Retrying.
============================================================================

> Could it be a PMTU problem ? (check
> http://git.kernel.org/?p=linux/kernel/git/davem/net.git;a=commit;h=9b04f350057863d1fad1ba071e09362a1da3503e )

I added the PMTU patch to kernel 3.6-rc2 - nothing changed.

Anything else to try?

Thanks,

Larry

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