linux-ext4 - [PATCH RFC v4 0/1] random: WARN on large getrandom() waits and introduce getrandom2()

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Date:   Wed, 18 Sep 2019 23:15:03 +0200
From:   "Ahmed S. Darwish" <darwish.07@...il.com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     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>,
        lkml <linux-kernel@...r.kernel.org>, linux-ext4@...r.kernel.org,
        linux-man@...r.kernel.org
Subject: [PATCH RFC v4 0/1] random: WARN on large getrandom() waits and
 introduce getrandom2()

Hi,

This is an RFC, and it obviously needs much more testing beside the
"it boots" smoke test I've just did.

Interestingly though, on my current system, the triggered WARN()
**reliably** makes the system get un-stuck... I know this is a very
crude heuristic, but I would personally prefer it to the other
proposals that were mentioned in this jumbo thread.

If I get an OK from Linus on this, I'll send a polished v5: further
real testing, kernel-parameters.txt docs, a new getrandom_wait(7)
manpage as referenced in the WARN() message, and extensions to the
getrandom(2) manpage for new getrandom2().

The new getrandom2() system call is basically a summary of Linus',
Lennart's, and Willy's proposals. Please see the patch #1 commit log,
and the "Link:" section inside it, for a rationale.

@Lennart, since you obviously represent user-space here, any further
notes on the new system call?

thanks,

Ahmed S. Darwish (1):
  random: WARN on large getrandom() waits and introduce getrandom2()

 drivers/char/Kconfig        | 60 ++++++++++++++++++++++++--
 drivers/char/random.c       | 85 ++++++++++++++++++++++++++++++++-----
 include/uapi/linux/random.h | 20 +++++++--
 3 files changed, 148 insertions(+), 17 deletions(-)

--
http://darwish.chasingpointers.com