From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 30900 invoked by alias); 4 Apr 2016 17:05:20 -0000 Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Received: (qmail 30870 invoked by uid 89); 4 Apr 2016 17:05:19 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=4.0 required=5.0 tests=AWL,BAYES_50,FREEMAIL_FROM,KAM_THEBAT,SPF_SOFTFAIL autolearn=no version=3.3.2 spammy=H*UA:Bat!, H*x:Bat!, H*r:sk:postmas, H*r:4.80.1 X-HELO: smtp.ht-systems.ru Received: from smtp.ht-systems.ru (HELO smtp.ht-systems.ru) (78.110.50.177) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES256-GCM-SHA384 encrypted) ESMTPS; Mon, 04 Apr 2016 17:05:09 +0000 Received: from [95.165.144.62] (helo=darkdragon.lan) by smtp.ht-systems.ru with esmtpa (Exim 4.80.1) (envelope-from ) (Authenticated sender: postmaster@rootdir.org) id 1an7vy-0000fS-3b ; Mon, 04 Apr 2016 20:05:02 +0300 Received: from [192.168.1.10] (HELO daemon2.darkdragon.lan) by daemon2 (Office Mail Server 0.8.12 build 08053101) with SMTP; Mon, 04 Apr 2016 16:51:11 -0000 Date: Mon, 04 Apr 2016 17:05:00 -0000 From: Andrey Repin Reply-To: cygwin@cygwin.com Message-ID: <59768064.20160404195111@yandex.ru> To: Corinna Vinschen , cygwin@cygwin.com Subject: Re: Unreliable flock In-Reply-To: <20160404151644.GB29337@calimero.vinschen.de> References: <175808986.20160403002257@yandex.ru> <20160404151644.GB29337@calimero.vinschen.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-IsSubscribed: yes X-SW-Source: 2016-04/txt/msg00067.txt.bz2 Greetings, Corinna Vinschen! >> The script (let's call it test.sh): >> >> #!/bin/dash -x >> _lock="./console-session.lock" >> { >> flock -n 9 || { >> echo "The $(cat "$_lock") command is running already." >> exit 3 >> } >&2 >> >> printf "$1" >&9 >> >> trap 'rm "$_lock";' EXIT HUP INT ABRT TERM >> >> sleep 20 >> >> } 9>> "$_lock" >> >> Very simple in essence. >> The one-liner: >> >> { flock -n 9 && sleep 10 || echo Fail;} 9>> ./console-session.lock >> >> Also extremely simple. >> >> Open two terminals. mintty or native, bash or dash, doesn't matter. >> chdir to the directory with the script. >> >> Start script in one terminal. ./test.sh >> Start oneliner in another terminal. Fail. How predictable! > I don't know what I'm doing wrong, but this WJFFM with Cygwin 2.4.1 > as well as 2.5.0. Additionally I tried to put the oneliner into a > script but it still WFM. It works for me, too. From time to time. But this work is completely unreliable. It may work five times, then fail ten times in a row. Most often it fails, if I run oneliner first. Almost 100%. > Apart from that, did you notice the flock restrictions outlined in > https://cygwin.com/cygwin-api/std-notes.html ? If you mean the part about > BSD file locks created via flock are only propagated to the direct parent > process, not to grand parents or sibling processes. The locks are only valid > in the creating process, its parent process, and subsequently started child > processes sharing the same file descriptor. then that's a showstopper. In short, it makes the function literally useless. I can work around it in a given script, but... *sad panda* Why they aren't real locks? What's use for "advisory locks"? "I think I may have a use for this file, but you are free to delete it, if you wish" ? -- With best regards, Andrey Repin Monday, April 4, 2016 19:27:11 Sorry for my terrible english... -- Problem reports: http://cygwin.com/problems.html FAQ: http://cygwin.com/faq/ Documentation: http://cygwin.com/docs.html Unsubscribe info: http://cygwin.com/ml/#unsubscribe-simple