Date: Sun, 28 Aug 2005 02:59:03 +0100 (BST) From: Robert Watson <rwatson@FreeBSD.org> To: "M. Warner Losh" <imp@bsdimp.com> Cc: bzeeb-lists@lists.zabbadoz.net, freebsd-current@FreeBSD.org, dandee@volny.cz Subject: Re: LOR route vr0 Message-ID: <20050828025721.X43518@fledge.watson.org> In-Reply-To: <20050827.124941.14976142.imp@bsdimp.com> References: <20050827181827.O24510@fledge.watson.org> <20050827.114013.35047360.imp@bsdimp.com> <20050827184153.A24510@fledge.watson.org> <20050827.124941.14976142.imp@bsdimp.com>
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On Sat, 27 Aug 2005, M. Warner Losh wrote: > : You need to add an entry to subr_witness.c creating a graph edge between > : the softc lock and the routing lock. An example of an entry in > : subr_witness.c: > : > : /* > : * TCP/IP > : */ > : { "tcp", &lock_class_mtx_sleep }, > : { "tcpinp", &lock_class_mtx_sleep }, > : { "so_snd", &lock_class_mtx_sleep }, > : { NULL, NULL }, > : > : Note that sets of ordered entries are terminated with a double-null. This > : declares that locks of type "tcp" preceed "tcpinp" which preceed > : "so_snd". > > So you have to have locks of type tcp BEFORE you take out tcpinp type > locks? Correct. 'tcp' reflects the global TCP state tables (pcbinfo) locks, and 'tcpinp' is for individual PCBs. If you acquire first a tcpinp and then tcp, the above settings should cause WITNESS to generate a lock order warning. Likewise, both tcp and tcpinp preceed so_snd, so if you acquire a protocol lock after a socket lock, it will get unhappy. WITNESS handles transitive relationships, so it gets connected up to the rest of the lock graph, explicit and implicit, so indirect violations of orders are fully handled. Robert N M Watson
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