Path: csiph.com!3.us.feeder.erje.net!feeder.erje.net!news.linkpendium.com!news.linkpendium.com!panix!usenet.stanford.edu!not-for-mail From: Chet Ramey Newsgroups: gnu.bash.bug Subject: Re: FIFO race condition on SunOS kernels Date: Mon, 31 Dec 2018 14:05:06 -0500 Organization: ITS, Case Western Reserve University Lines: 45 Approved: bug-bash@gnu.org Message-ID: References: Reply-To: chet.ramey@case.edu NNTP-Posting-Host: lists.gnu.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Trace: usenet.stanford.edu 1546283127 4984 208.118.235.17 (31 Dec 2018 19:05:27 GMT) X-Complaints-To: action@cs.stanford.edu Cc: chet.ramey@case.edu To: Martijn Dekker , Bug reports for the GNU Bourne Again SHell Envelope-to: bug-bash@gnu.org X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:reply-to:cc:subject:to:references:from:openpgp :autocrypt:organization:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; 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Intel Mac OS X 10.14; rv:60.0) Gecko/20100101 Thunderbird/60.3.3 In-Reply-To: Content-Language: en-US X-Junkmail-Status: score=7/90, host=mpv2-2015.case.edu X-Junkmail-PrAS-Raw: score=7/90, refid=2.7.2:2018.12.31.180616:17:7.944, ip=, rules=__YOUTUBE_RCVD, __X_GOOGLE_DKIM_SIGNATURE, __HAS_REPLYTO, __HAS_CC_HDR, __SUBJ_REPLY, __BOUNCE_CHALLENGE_SUBJ, __BOUNCE_NDR_SUBJ_EXEMPT, __SUBJ_ALPHA_END, __TO_MALFORMED_2, __TO_NAME, __TO_NAME_DIFF_FROM_ACC, __REFERENCES, __HAS_FROM, FROM_EDU_TLD, __HAS_MSGID, __SANE_MSGID, DATE_TZ_NA, __USER_AGENT, __MOZILLA_USER_AGENT, __MIME_VERSION, __IN_REP_TO, __CT, __CT_TEXT_PLAIN, __CTE, __REPLYTO_SAMEAS_FROM_ADDY, __REPLYTO_SAMEAS_FROM_ACC, __FROM_DOMAIN_IN_ANY_CC1, __FROM_DOMAIN_IN_ANY_CC2, __REPLYTO_SAMEAS_FROM_DOMAIN, __ANY_URI, __URI_WITH_PATH, __URI_NO_WWW, __HIGHBITS, __CP_URI_IN_BODY, __FRAUD_MONEY_CURRENCY_DOLLAR, __SUBJ_ALPHA_NEGATE, __URI_IN_BODY, __URI_NOT_IMG, __FORWARDED_MSG, __NO_HTML_TAG_RAW, BODY_SIZE_1700_1799, BODYTEXTP_SIZE_3000_LESS, __MIME_TEXT_P1, __MIME_TEXT_ONLY, __URI_NS, HTML_00_01, HTML_00_10, __FRAUD_MONEY_CURRENCY, [TRUNCATED], so=2010-03-03 19:42:08, dmn=2016-08-03-0138 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.4.x-2.6.x [generic] [fuzzy] X-Received-From: 129.22.103.227 X-BeenThere: bug-bash@gnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: Bug reports for the GNU Bourne Again SHell List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Xref: csiph.com gnu.bash.bug:15020 On 12/31/18 12:37 PM, Martijn Dekker wrote: > You'd think that establishing a pipe between two processes is a very basic > UNIX feature that should work reliably on all UNIX variants. > > But the following script seems to break consistently on Solaris and > variants (SunOS kernels) when executed by bash, ksh93, or dash. All it does > is make 100 FIFOs and read a line from each -- it should be trivial. > > And it does work fine on (recent versions of) Linux, macOS, and all the > BSDs, on all shells. > > #! /bin/sh > tmpdir=/tmp/FIFOs$$ > trap "exec rm -rf $tmpdir" EXIT INT PIPE TERM > mkdir "$tmpdir" || exit > i=0; while test "$((i+=1))" -le 100; do >         fifo=$tmpdir/FIFO$i >         mkfifo "$fifo" || exit >         echo "this is FIFO $i" >"$fifo" & >         read foo <"$fifo" && echo "$foo" > done > > Tested on Solaris 10.1, 11.3 and 11.4 and on OpenIndiana, all on > VirtualBox. They all fail in identical ways. > > ksh93 (which is /bin/sh on Solaris) doesn't cope with the script either but > hangs slightly later. dash goes through all of them bust most fail with > 'interrupted system call'. However, zsh, yash, and /usr/xpg4/bin/sh (ksh88) > execute the script correctly on Solaris -- but about 20 times as slowly as > on other OSs. > > This makes me suspect the SunOS kernel must have some very bad race > condition involving FIFOs, but some shells work around it. > > Would it be possible to fix this on bash 5? Maybe as a patch, when I have some time to investigate it. Chet -- ``The lyf so short, the craft so long to lerne.'' - Chaucer ``Ars longa, vita brevis'' - Hippocrates Chet Ramey, UTech, CWRU chet@case.edu http://tiswww.cwru.edu/~chet/