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From:   Stephan =?ISO-8859-1?Q?M=FCller?= <smueller@chronox.de>
To:     kbuild test robot <lkp@intel.com>
Cc:     kbuild-all@lists.01.org, Arnd Bergmann <arnd@arndb.de>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        linux-crypto@vger.kernel.org, LKML <linux-kernel@vger.kernel.org>,
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        "Eric W. Biederman" <ebiederm@xmission.com>,
        "Alexander E. Patrakov" <patrakov@gmail.com>,
        "Ahmed S. Darwish" <darwish.07@gmail.com>,
        "Theodore Y. Ts'o" <tytso@mit.edu>, Willy Tarreau <w@1wt.eu>,
        Matthew Garrett <mjg59@srcf.ucam.org>,
        Vito Caputo <vcaputo@pengaru.com>,
        Andreas Dilger <adilger.kernel@dilger.ca>,
        Jan Kara <jack@suse.cz>, Ray Strode <rstrode@redhat.com>,
        William Jon McCann <mccann@jhu.edu>,
        zhangjs <zachary@baishancloud.com>,
        Andy Lutomirski <luto@kernel.org>,
        Florian Weimer <fweimer@redhat.com>,
        Lennart Poettering <mzxreary@0pointer.de>,
        Nicolai Stange <nstange@suse.de>,
        "Peter, Matthias" <matthias.peter@bsi.bund.de>,
        Marcelo Henrique Cerri <marcelo.cerri@canonical.com>,
        Roman Drahtmueller <draht@schaltsekun.de>,
        Neil Horman <nhorman@redhat.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Julia Lawall <julia.lawall@inria.fr>
Subject: Re: [PATCH v27 04/12] LRNG - add switchable DRNG support
Date:   Sun, 12 Jan 2020 11:12:49 +0100
Message-ID: <6344127.aaDc98gsnP@positron.chronox.de>
In-Reply-To: <202001111540.5y2emdGQ%lkp@intel.com>
References: <5087131.2PHHu6SUIE@positron.chronox.de> <202001111540.5y2emdGQ%lkp@intel.com>
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Am Samstag, 11. Januar 2020, 08:09:50 CET schrieb kbuild test robot:

Hi,

> Hi "Stephan,
>=20
> Thank you for the patch! Perhaps something to improve:
>=20
> [auto build test WARNING on char-misc/char-misc-testing]
> [also build test WARNING on cryptodev/master crypto/master v5.5-rc5
> next-20200110] [if your patch is applied to the wrong git tree, please dr=
op
> us a note to help improve the system. BTW, we also suggest to use '--base'
> option to specify the base tree in git format-patch, please see
> https://stackoverflow.com/a/37406982]
>=20
> url:  =20
> https://github.com/0day-ci/linux/commits/Stephan-M-ller/dev-random-a-new-=
ap
> proach-with-full-SP800-90B/20200110-084934 base: =20
> https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
> 68faa679b8be1a74e6663c21c3a9d25d32f1c079 reproduce:
>         # apt-get install sparse
>         # sparse version: v0.6.1-129-g341daf20-dirty
>         make ARCH=3Dx86_64 allmodconfig
>         make C=3D1 CF=3D'-fdiagnostic-prefix -D__CHECK_ENDIAN__'
>=20
> If you fix the issue, kindly add following tag
> Reported-by: kbuild test robot <lkp@intel.com>
>=20
>=20
> sparse warnings: (new ones prefixed by >>)
>=20
> >> drivers/char/lrng/lrng_internal.h:239:39: sparse: sparse: context
> >> imbalance in 'lrng_drng_switch' - unexpected unlock
> vim +/lrng_drng_switch +239 drivers/char/lrng/lrng_internal.h
>=20
> 58c283819a1e87 Stephan M=FCller 2020-01-09  233
> 58c283819a1e87 Stephan M=FCller 2020-01-09  234  /* Unlock the DRNG */
> 58c283819a1e87 Stephan M=FCller 2020-01-09  235  static __always_inline v=
oid
> lrng_drng_unlock(struct lrng_drng *drng, 58c283819a1e87 Stephan M=FCller
> 2020-01-09  236  					     unsigned long *flags)=20
58c283819a1e87 Stephan
> M=FCller 2020-01-09  237  {
> 58c283819a1e87 Stephan M=FCller 2020-01-09  238  	if
> (lrng_drng_is_atomic(drng)) 58c283819a1e87 Stephan M=FCller 2020-01-09 @2=
39=20
> 		spin_unlock_irqrestore(&drng->spin_lock, *flags); 58c283819a1e87=20
Stephan
> M=FCller 2020-01-09  240  	else
> 58c283819a1e87 Stephan M=FCller 2020-01-09  241  		mutex_unlock(&drng-
>lock);
> 58c283819a1e87 Stephan M=FCller 2020-01-09  242  }
> 58c283819a1e87 Stephan M=FCller 2020-01-09  243
>=20
> :::::: The code at line 239 was first introduced by commit
> :::::: 58c283819a1e879bc2e30d05720285f9709f7f6d Linux Random Number
> :::::: Generator
> ::::::=20
> :::::: TO: Stephan M=FCller <smueller@chronox.de>
> :::::: CC: 0day robot <lkp@intel.com>
>=20
> ---
> 0-DAY kernel test infrastructure                 Open Source Technology
> Center https://lists.01.org/hyperkitty/list/kbuild-all@lists.01.org Intel
> Corporation

After analyzing the issue a bit more, it seems that I have to remove=20
"unlikely" from lrng_drng_lock which seems to cause additional grief
with sparse. Note, sparse will still report a lock context imbalance as it
used to since we indeed have two lock context as documented in
lrng_drng_switch.

Ciao
Stephan