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Subject: Re: [PATCH 1/4] fs: Implement close-on-fork
To:     "Karstens, Nate" <Nate.Karstens@garmin.com>,
        Matthew Wilcox <willy@infradead.org>
Cc:     Alexander Viro <viro@zeniv.linux.org.uk>,
        Jeff Layton <jlayton@kernel.org>,
        "J. Bruce Fields" <bfields@fieldses.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Richard Henderson <rth@twiddle.net>,
        Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
        Matt Turner <mattst88@gmail.com>,
        "James E.J. Bottomley" <James.Bottomley@hansenpartnership.com>,
        Helge Deller <deller@gmx.de>,
        "David S. Miller" <davem@davemloft.net>,
        Jakub Kicinski <kuba@kernel.org>,
        "linux-fsdevel@vger.kernel.org" <linux-fsdevel@vger.kernel.org>,
        "linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
        "linux-alpha@vger.kernel.org" <linux-alpha@vger.kernel.org>,
        "linux-parisc@vger.kernel.org" <linux-parisc@vger.kernel.org>,
        "sparclinux@vger.kernel.org" <sparclinux@vger.kernel.org>,
        "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        David Laight <David.Laight@aculab.com>,
        Changli Gao <xiaosuo@gmail.com>
References: <20200420071548.62112-1-nate.karstens@garmin.com>
 <20200420071548.62112-2-nate.karstens@garmin.com>
 <fa6c5c9c7c434f878c94a7c984cd43ba@garmin.com>
 <20200422154356.GU5820@bombadil.infradead.org>
 <6ed7bd08892b4311b70636658321904f@garmin.com>
From:   Bernd Petrovitsch <bernd@petrovitsch.priv.at>
Message-ID: <97f05204-a27c-7cc8-429a-edcf6eebaa11@petrovitsch.priv.at>
Date:   Wed, 22 Apr 2020 16:31:34 +0000
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On 22/04/2020 16:02, Karstens, Nate wrote:
>> It's not safe to call system() from a threaded app.  That's all.  It's=
 right there in the DESCRIPTION:
>=20
> That is true, but that description is missing from both the Linux man p=
age and the glibc documentation (https://www.gnu.org/software/libc/manual=
/html_mono/libc.html#Running-a-Command). It seems like a minor point that=
 won't be noticed until it causes a problem, and problems are rare enough=
 they might go unnoticed for a while. We have removed system() from our a=
pplication, but we're also concerned that libraries we integrate will use=
 system() without our knowledge.

Reimplementing system() is trivial.
LD_LIBRARY_PRELOAD should take care of all system(3) calls.

I wonder it it has some value to add runtime checking for
"multi-threaded" to such lib functions and error out if
yes.

Apart from that, system() is a PITA even on
single/non-threaded apps.

MfG,
	Bernd
--=20
There is no cloud, just other people computers.
-- https://static.fsf.org/nosvn/stickers/thereisnocloud.svg

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