Date: Fri, 01 Sep 2006 18:20:58 +0200 From: =?UTF-8?B?VsOhY2xhdiBIYWlzbWFu?= <V.Haisman@sh.cvut.cz> To: Robert Watson <rwatson@FreeBSD.org> Cc: freebsd-stable@freebsd.org Subject: Re: malloc(M_WAITOK) of "g_bio", forcing M_NOWAIT with non-sleepable locks held: Message-ID: <44F85DEA.2010206@sh.cvut.cz> In-Reply-To: <20060901104141.J4921@fledge.watson.org> References: <44F67DC2.1060900@sh.cvut.cz> <20060901104141.J4921@fledge.watson.org>
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[-- Attachment #1 --] Robert Watson wrote, On 1.9.2006 11:46: > > On Thu, 31 Aug 2006, Václav Haisman wrote: > >> I found this in logs of 6.1 box that I admin this morning. The machine >> keeps running after that. > > Indeed, there does appear to be a problem in the TCP socket option code > with respect to performing copyin/copyout while holding the inpcb lock. > This problem is not present in the IP layer socket option code. > However, the code between HEAD and 6-STABLE here differs significantly, > so fixing this will require different changes in the two branches. > Could you file a problem report on this, and forward me the PR receipt? > I'm on travel in India currently, with mixed connectivity, so it may be > a little bit before I can get to fixing the problem. > > In principle, the risk here is a deadlock, but the fix is a little > complicated as if we release the lock there, the state of the TCP socket > can change, so when the code picks up from the copyin/copyout, it needs > to validate that the operation is still valid on the socket (i.e., the > connection hasn't been reset during the system call -- perhaps while the > application is blocked waiting on disk i/o for a paged out page that > contains the socket option). This is very unlikely to trigger in > practice, the warning there is quite conservative, but needs to be > addressed properly. > > Thanks for the report, > > Robert N M Watson > Computer Laboratory > University of Cambridge Here is the PR: http://www.freebsd.org/cgi/query-pr.cgi?pr=102752 -- Vaclav Haisman [-- Attachment #2 --] -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.4 (MingW32) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iQEVAwUBRPhd/kNOZDESBK8FAQIKtQf+JVl57cOxPsmlhjVU22tJCr/WloqCkCFK 9f4928WY+9Tgk3qRzZtg7WW/kdA6f/kUZt8AKUOFXNS1euj0JGIQKOfFOt21Wz/B mtpkCdupBdzmN5AVmSRzGwaMKPOwDeK8DVjz4jDcQR8uJweDvC5sOVyKlocS9UGk M6oSfzOxyXSg8Od7D1VX7CzCdsWqZtz5x+cE0rHvhAkoB1nL3ojbfpvBKqNtvc7d vgGu3T+DK/l2W6PD/5iQ9Kgj+Nu0CN2T1Z3oT9Q1sPU6snXsrMSfBlZw/n4MEW5J uxDAQwSCp64H+sp5TjdzutM7dNRxBq0vUfEzXLWacn7RBk8FHVepXQ== =sXi6 -----END PGP SIGNATURE-----
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