linux-kernel - Re: [PATCH RFC v4 1/1] random: WARN on large getrandom() waits and introduce getrandom2()

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Message-ID: <20190920175646.GA6969@pc>
Date:   Fri, 20 Sep 2019 19:56:46 +0200
From:   "Ahmed S. Darwish" <darwish.07@...il.com>
To:     Willy Tarreau <w@....eu>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Lennart Poettering <mzxreary@...inter.de>,
        "Theodore Y. Ts'o" <tytso@....edu>,
        "Eric W. Biederman" <ebiederm@...ssion.com>,
        "Alexander E. Patrakov" <patrakov@...il.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Matthew Garrett <mjg59@...f.ucam.org>,
        lkml <linux-kernel@...r.kernel.org>, linux-ext4@...r.kernel.org,
        linux-api@...r.kernel.org, linux-man@...r.kernel.org
Subject: Re: [PATCH RFC v4 1/1] random: WARN on large getrandom() waits and
 introduce getrandom2()

On Fri, Sep 20, 2019 at 07:26:09PM +0200, Willy Tarreau wrote:
> Hi Ahmed,
> 
> On Fri, Sep 20, 2019 at 03:46:09PM +0200, Ahmed S. Darwish wrote:
> > Problem is, glibc is still *really* slow in adopting linux syscall
> > wrappers, so I'm not optimistic about that...
> >
> > I still see the new system call as the sanest path, even provided
> > the cost of a new syscall number..
> 
> New syscalls are always a pain to deal with in userland, because when
> they are introduced, everyone wants them long before they're available
> in glibc. So userland has to define NR_xxx for each supported arch and
> to perform the call itself.
> 
> With flags adoption is instantaneous. Just #ifndef/#define, check if
> the flag is supported and that's done. The only valid reason for a new
> syscall is when the API changes (e.g. one extra arg, a la accept4()),
> which doesn't seem to be the case here. Otherwise please by all means
> avoid this in general.
> 

I see. Thanks a lot for the explanation above :)

--
Ahmed Darwish