linux-kernel - Re: Linux 5.3-rc8

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Date:   Thu, 12 Sep 2019 00:37:47 +0200
From:   "Ahmed S. Darwish" <darwish.07@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     "Theodore Y. Ts'o" <tytso@....edu>,
        Andreas Dilger <adilger.kernel@...ger.ca>,
        Jan Kara <jack@...e.cz>, Ray Strode <rstrode@...hat.com>,
        William Jon McCann <mccann@....edu>,
        zhangjs <zachary@...shancloud.com>, linux-ext4@...r.kernel.org,
        lkml <linux-kernel@...r.kernel.org>
Subject: Re: Linux 5.3-rc8

On Wed, Sep 11, 2019 at 11:41:44PM +0200, Ahmed S. Darwish wrote:
> On Wed, Sep 11, 2019 at 05:45:38PM +0100, Linus Torvalds wrote:
[...]
> >
> > Well, even on a PC, sometimes rdrand just isn't there. AMD has screwed
> > it up a few times, and older Intel chips just don't have it.
> > 
> > So I'd be inclined to either lower the limit regardless -
> 
> ACK :)
> 
> > and perhaps make the "user space asked for randomness much too
> > early" be a big *warning* instead of being a basically fatal hung
> > machine?
> 
> Hmmm, regarding "randomness request much too early", how much is time
> really a factor here?
> 
> I tested leaving the machine even for 15+ minutes, and it still didn't
> continue booting: the boot is practically blocked forever...
> 
> Or is the thoery that hopefully once the machine is un-stuck, more
> sources of entropy will be available? If that's the case, then
> possibly (rate-limited):
> 
>   "urandom: process XX asked for YY bytes. CRNG not yet initialized"
>
     ^
     getrandom: ....

(since urandom always succeeds, even if CRNG is not inited, and
 it already prints a very similar warning in that case anyway..)

thanks,
--darwi