linux-kernel - Re: [RFC patch] sctp: sctp_generate_fwdtsn: Initialize sctp_fwdtsn

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Message-ID: <20150703115105.GA3503@hmsreliant.think-freely.org>
Date:	Fri, 3 Jul 2015 07:51:05 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Joe Perches <joe@...ches.com>
Cc:	Vlad Yasevich <vyasevich@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	linux-sctp@...r.kernel.org, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC patch] sctp: sctp_generate_fwdtsn: Initialize
 sctp_fwdtsn_skip array, neatening

On Thu, Jul 02, 2015 at 02:54:56PM -0700, Joe Perches wrote:
> It's not clear to me that the sctp_fwdtsn_skip array is
> always initialized when used.
> 
> It is appropriate to initialize the array to 0?
> 
> This patch initializes the array too 0 and moves the
> local variables into the blocks where used.
> 
> It also does some miscellaneous neatening by using
> continue; and unindenting the following block and
> using ARRAY_SIZE rather than 10 to decouple the
> array declaration size from a constant.
> ---
We don't set ftsn_skip_arr to a known value because we limit the amount of
elements that get read from it prior to those elements being set.  That is to
say, in our first use (the call to sctp_get_skip_pos), we pass the uninitialized
array, and the nskips value, which is initalized to 0.  Looking at the
definition of sctp_get_skip_pos, the for loop there becomes a nop, meaning the
uninitalized array is irrelevant, as we never visit any of its elements.
element zero is returned, and thats what the for_each loop in
sctp_generate_fwdtsn sets in that element of the array.  On the next iteration
of the for_each loop, we call sctp_get_skip_pos with nskips = 1, so only the
first element is visited, whcih was set by the previous loop iteration.


The rest of the cleanups look ok I think.  Can you tell me what you did to test
it?

Regards
Neil

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