Re: [PATCH v3] getrandom system call wrapper [BZ #17252]

[Florian Weimer <fweimer at redhat dot com>]

On 09/12/2016 09:25 AM, Florian Weimer wrote:
> On 09/09/2016 05:23 PM, Torvald Riegel wrote:
> > On Fri, 2016-09-09 at 16:28 +0200, Florian Weimer wrote:
> > > On 09/09/2016 04:21 PM, Torvald Riegel wrote:
> > > > On Thu, 2016-09-08 at 13:44 +0200, Florian Weimer wrote:
> > > > > I have made the system call wrapper a cancellation point.  (If we
> > > > > implement the simpler getentropy interface, it would not be a
> > > > > cancellation point.)
> > > >
> > > > Why did you do that?
> > >
> > > I have to, because it can block indefinitely.
> >
> > That doesn't mean you have to make the default function a cancellation
> > point.  There are many POSIX functions which can block indefinitely and
> > which are not required to be cancellation points (eg, rwlocks only *may*
> > be cancellation points).
> >
> > Can the system call really block indefinitely, or only for a long time
> > and (ie, will return eventually)?
>
> Yes, if the system enters a deadlock condition where the waiting for
> randomness prevents it from accumulating additional randomness.

This is what happens here:

  <https://bugzilla.redhat.com/show_bug.cgi?id=1383060>

systemd will eventually kill the blocked process and the boot continues, 
but all network services will be missing.

Florian