Date: Tue, 10 Feb 2009 18:40:02 GMT From: Ed Schouten <ed@80386.nl> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/118287: [kernel] [patch] tty write is not always atomic for small lines Message-ID: <200902101840.n1AIe2cS083948@freefall.freebsd.org>
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The following reply was made to PR kern/118287; it has been noted by GNATS. From: Ed Schouten <ed@80386.nl> To: bug-followup@FreeBSD.org, chardin@2wire.com Cc: rwatson@FreeBSD.org Subject: Re: kern/118287: [kernel] [patch] tty write is not always atomic for small lines Date: Tue, 10 Feb 2009 19:32:17 +0100 --RwGu8mu1E+uYXPWP Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable Hello Charles, Robert Watson poked me to take a look at this PR. Unfortunately the new TTY layer still has the same `guarantees', so this problem still exists. The fix you proposed sounds pretty good in theory, but as you mentioned, it only solves a certain class of races. The problem is that output processing may cause data to grow 8 times, because of tab expansion. What's your opinion on this patch? http://80386.nl/pub/tty-sync.diff It adds synchronisation to the call to ttydisc_write(), which should be pretty solid. Because I want to keep non-blocking writes as they are now, they can still cause data to get mangled, but I guess this is already pretty good. --=20 Ed Schouten <ed@80386.nl> WWW: http://80386.nl/ --RwGu8mu1E+uYXPWP Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEARECAAYFAkmRyDEACgkQ52SDGA2eCwVscwCfSvYGx0aC4aVouf1frP3QaqHf GIIAn33vIUgCYz6twqtdnBq/GbiAKLbQ =nknL -----END PGP SIGNATURE----- --RwGu8mu1E+uYXPWP--
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