Date: Mon, 6 Oct 2003 19:10:25 -0400 (EDT) From: Daniel Eischen <eischen@vigrid.com> To: Dan Langille <dan@langille.org> Cc: hackers@freebsd.org Subject: Re: [PATCH] : libc_r/uthread/uthread_write.c Message-ID: <Pine.GSO.4.10.10310061909030.12602-100000@pcnet5.pcnet.com> In-Reply-To: <3F77D27E.6203.3321BA14@localhost>
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Is your mailer screwed up? We're getting duplicates (a few days later). On Mon, 29 Sep 2003, Dan Langille wrote: > On 18 Sep 2003 at 7:50, Daniel Eischen wrote: > > > On Wed, 17 Sep 2003, Dan Langille wrote: > > > > > On 16 Sep 2003 at 20:49, Daniel Eischen wrote: > > > > > > > On Tue, 16 Sep 2003, Dan Langille wrote: > > > > > > > > > I've had preliminary success with this patch. More testing needs > > > > > to be done, but in the meantime, I would appreciate reviews and > > > > > comments. The patched code is available from > > > > > http://beta.freebsddiary.org/tmp/uthread_write.c and the patch > > > > > appears below. > > > > > > > > > > In short, the logic has been changed to ensure that if __sys_write > > > > > returns zero, this value is returned by _write. > > > > > > > > I think this is not quite correct. Since libc_r is looping > > > > and some data may have been read, then the partial byte count > > > > should be returned, not zero. It is possible the partial byte > > > > count could also be zero in some cases, so it would result > > > > in zero being returned in those instances. > > > > > > I see what you mean. Please have a look at > > > http://beta.freebsddiary.org/tmp/uthread_write.c2 > > > The patch appears at the end of this message. > > > > Right, this seems correct to me. > > All our testing on this patch has been successful. I'm going to do a > few more tests on different hardware under 4.8-stable. > > What's the next step? Commit it? Get others to test with it first? > > > > > I think the problem lies with the SCSI tape device. It should > > > > either return 0 or -1 with errno=ENOSPC on a write that detects > > > > an EOT, not partial byte count. > > > > > > You are referring to sa(4)? > > > > Yes. > > > > > > If you are using libkse or > > > > libthr, you will get a partial byte count and not zero because > > > > the tape driver returns the (partial) bytes written. So exiting > > > > the loop in libc_r and returning 0 would only seem to correct > > > > the "problem" for libc_r. > > > > If there is a difference, it could be because libc_r is using non-blocking > > IO behind the scenes, and sa(4) may be returning partial byte count > > in the non-blocking case and 0 (or -1 and ENOSPC) in the blocking case > > (which is what you'd get using libkse/libthr). > > > > > The problem found when running under pthreads on 4.8-stable [i.e. > > > EOT is not returned to the application code] is not found with libkse > > > on 5.1-current. > > FWIW: our regression tests are failing under 5.1 and we suspect that > MTIOCERRSTAT ioctl() has changed since 4.8. We're getting: > > btape: dev.c:1119 Doing MTIOCERRSTAT errno=22 ERR=Invalid argument > > We'll continue with our 5.1 work, but we'd like to finish up with 4.8 > ASAP. > -- > Dan Langille : http://www.langille.org/ > > _______________________________________________ > freebsd-hackers@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-hackers > To unsubscribe, send any mail to "freebsd-hackers-unsubscribe@freebsd.org" > -- "Some folks are into open source, but me, I'm into open bar." -- Spencer F. Katt
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