Date: Wed, 28 Jun 2006 17:17:33 +0200 From: Stanislaw Halik <sthalik@tehran.lain.pl> To: freebsd-stable@freebsd.org Subject: Re: trap 12: supervisor write, page not present on 6.1-STABLE Tue May 16 2006 Message-ID: <20060628151733.GA787@tehran.lain.pl> In-Reply-To: <20060628101405.I50845@fledge.watson.org> References: <20060627045310.GA6324@tehran.lain.pl> <20060627140946.J273@fledge.watson.org> <20060627134134.GA23337@tehran.lain.pl> <20060628101405.I50845@fledge.watson.org>
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--9amGYk9869ThD9tj Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Jun 28, 2006, Robert Watson wrote: >>>> 6.1-STABLE crashed on me. I'm providing a backtrace. Could any of you, >>>> experienced people, suggest me if it's a hardware problem or is it an >>>> error inside the OS? >>> This is a known bug in the TCP code; a large set of outstanding changes= =20 >>> is present in 7.x that will fix the problem when merged. However, I=20 >>> recently had push-back on merging the larger batch of changes, so am=20 >>> looking at merging a workaround that will also correct the problem=20 >>> without the larger set of architectural changes. I hope to have a chan= ce=20 >>> to look at that in detail this weekend. >> I'm glad to know that it isn't either unknown or hardware-related. Thank= =20 >> you for your prompt reply! > Per my earlier e-mail, I had hoped to merge a larger set of changes from= =20 > HEAD that resolve the underlying problem here (that inpcb's can be detach= ed=20 > from a socket while the socket is still in use), but right now I'm=20 > deferring merging those changes as they are somewhat risky (as they are= =20 > large). Instead, I've produced a candidate work-around patch, now attach= ed=20 > to kern/97095. This does not fix the underlying problem, but seeks to=20 > narrow the window for the race to be exercised by avoiding caching a=20 > volatile pointer across user memory copying, which under load can result = in=20 > blocking I/O. I would be quite interested in knowing if this resolves th= e=20 > problem in practice -- if so, it's a definite short-term merge candidate = to=20 > reduce the symptoms of this problem until the proper fix can be merged. > http://www.watson.org/~robert/freebsd/netperf/20060628-ip_ctloutput.diff Thank you for the patch. I'll let you know in few days if the crash occurs again. It's quite reproducible (crashed yesterday in the same code path). --9amGYk9869ThD9tj Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.4 (FreeBSD) iD8DBQFEop2NadU+vjT62TERAgMCAJ0dnVFFEKy4jKHDl1zF0TAOKaaHhACeJGYs XiAUiw8xgibEaCpGRSjKaHI= =kaWo -----END PGP SIGNATURE----- --9amGYk9869ThD9tj--
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