X-Recipient: archive-cygwin@delorie.com X-SWARE-Spam-Status: No, hits=-1.7 required=5.0 tests=AWL,BAYES_00,RCVD_IN_DNSWL_NONE,UNPARSEABLE_RELAY X-Spam-Check-By: sourceware.org X-Yahoo-SMTP: jenXL62swBAWhMTL3wnej93oaS0ClBQOAKs8jbEbx_o- Date: Mon, 7 Mar 2011 10:37:08 -0500 From: Christopher Faylor To: cygwin@cygwin.com Subject: Re: 1.7.8: write fails with EAGAIN Message-ID: <20110307153708.GA2538@ednor.casa.cgf.cx> Reply-To: cygwin@cygwin.com Mail-Followup-To: cygwin@cygwin.com References: <4D72992D.4090007@tweerlei.de> <20110307103951.GL6393@calimero.vinschen.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20110307103951.GL6393@calimero.vinschen.de> User-Agent: Mutt/1.5.20 (2009-06-14) Mailing-List: contact cygwin-help@cygwin.com; run by ezmlm Precedence: bulk List-Id: List-Unsubscribe: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: cygwin-owner@cygwin.com Mail-Followup-To: cygwin@cygwin.com Delivered-To: mailing list cygwin@cygwin.com On Mon, Mar 07, 2011 at 11:39:51AM +0100, Corinna Vinschen wrote: >On Mar 5 21:12, Robert Wruck wrote: >> Hi, >> >> recently, I found that cygwin-git was not able to 'cat-file' files >> that exceeded some size (in my case about 80MB). >> I tracked this down to the cygwin implementation of write() that >> behaves quite odd in some cases. >> >> I wrote a small program (source attached) that mmaps a given file >> and tries to write it to another file or stdout. >> >> The results vary: >> >> If the destination is a file (`writetest infile outfile` or >> `writetest infile > outfile`), the write succeeds in a single call. >> >> If the destination is a pipe (`writetest infile | cat > outfile`), >> the write succeeds in most cases. BUT: >> >> Under WinXP (XP Service Pack 2, 32bit), the call returns -1 and >> errno=EAGAIN. Nevertheless, SOME data is written to the pipe (in my >> case 4096 byte for each call). >> This breaks git since it does an infinite loop while errno=EAGAIN. > >Hang on, you are saying that a *blocking* write(2) to a pipe returns >with EAGAIN? Are you sure? It would be quite a surprise if git would >actually do that. EAGAIN is only an expected error for non-blocking >I/O, so applications which use blocking I/O usually only test for EINTR. I can barely convince myself that there's a pathological case where an EAGAIN could leak out. I'm investigating now. cgf -- 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