linux-kernel - Re: randconfig build error with next-20150529, in crypto/jitterentropy.c

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Date:	Mon, 08 Jun 2015 17:52:49 +0200
From:	Stephan Mueller <smueller@...onox.de>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Herbert Xu <herbert@...dor.apana.org.au>,
	Andy Shevchenko <andy.shevchenko@...il.com>,
	Jim Davis <jim.epost@...il.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-next <linux-next@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	linux-crypto <linux-crypto@...r.kernel.org>,
	Waiman Long <Waiman.Long@...com>,
	Ingo Molnar <mingo@...nel.org>,
	"x86@...nel.org" <x86@...nel.org>
Subject: Re: randconfig build error with next-20150529, in crypto/jitterentropy.c

Am Monday 08 June 2015, 14:36:30 schrieb Peter Zijlstra:

Hi Peter,
>
>Would something like
>
>#pragma GCC push_options
>#pragma GCC optimize ("-O0")
>static __u64 jent_fold_time(struct rand_data *ec, __u64 time,
>			    __u64 *folded, __u64 loop_cnt)
>{
>	...
>}
>#pragma GCC pop_options
>
>Be an option to allow the file to be compiled with regular optimizations
>enabled?

After doing some tests, I see that neither the min entropy nor the Shannon 
Entropy of the raw noise is affected by using the mentioned pragmas at the 
right locations.

So I will prepare a patch tonight.

Just for my edification: why does an -O0 on a self contained file break the 
compile run? Any why do the pragmas work?

Thanks
Stephan
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