Date: Thu, 06 Aug 2009 11:58:37 -0700 From: Julian Elischer <julian@elischer.org> To: Rick Macklem <rmacklem@uoguelph.ca> Cc: Robert Watson <rwatson@FreeBSD.org>, jeff@FreeBSD.org, "Bjoern A. Zeeb" <bz@FreeBSD.org>, freebsd-current@FreeBSD.org, kib@FreeBSD.org, Navdeep Parhar <np@FreeBSD.org>, Larry Rosenman <ler@lerctr.org>, lstewart@FreeBSD.org Subject: Re: reproducible panic in netisr Message-ID: <4A7B27DD.20503@elischer.org> In-Reply-To: <Pine.GSO.4.63.0908061131220.3240@muncher.cs.uoguelph.ca> References: <20090804225806.GA54680@hub.freebsd.org> <20090805054115.O93661@maildrop.int.zabbadoz.net> <20090805063417.GA10969@doormat.home> <alpine.BSF.2.00.0908060011490.59996@fledge.watson.org> <alpine.BSF.2.00.0908060834120.21318@thebighonker.lerctr.org> <alpine.BSF.2.00.0908061508520.62916@fledge.watson.org> <Pine.GSO.4.63.0908061038120.22077@muncher.cs.uoguelph.ca> <4A7AF25D.40608@elischer.org> <Pine.GSO.4.63.0908061131220.3240@muncher.cs.uoguelph.ca>
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Rick Macklem wrote: > > > On Thu, 6 Aug 2009, Julian Elischer wrote: > >> Rick Macklem wrote: >>> >>> >>> On Thu, 6 Aug 2009, Robert Watson wrote: >>> >>>> other places where we have very strong alignment requirements on >>>> i386/amd64, such as the td_ucred pointer that we check for change on >>>> system calls/traps to see if we need to refresh the thread's >>>> credential from the process credential. >>>> >>> Does this imply that the krpc/nlm/nfs hack of: >>> oldcred = td->td_ucred; >>> td->td_ucred = "some other cred ptr, such as the mount one" >>> ... >>> td->td_ucred = oldcred; >>> >>> could be dangerous? >>> >>> Maybe it should be converted to code that replaces the contents instead >>> of replacing the *cred? (Variants of the above live in a bunch of places >>> in the krpc, nlm and nfs code, due to the fact that the socket functions >>> use td->td_ucred in various places.) >> >> no, creds are read-only .. you never change a cred. >> You alwasy make a new one ans use it, becasue you may be shareing your >> cred with hundreds of other sibling threads or processes. (they are >> refcounted) >> > Righto, yes. So does that imply that the alignment provided by crget() > { which uses malloc() } is sufficient for td->td_ucred or is td->td_ucred > a special case? It should be enough. > > rick > ps: The above hack, which came up in a separate discussion yesterday, > isn't gonna be easy to get rid of, imho. A whole bunch of network > related functions use td->td_ucred and the only fix I can see would > be to add "*cred" arguments to them all, so that the krpc/nlm/nfs > code could pass the correct *cred in. (It is set to the one used at > mount time for network reconnects, etc.) we should probably do the right thign refcount-wise for the ucred but refcount (atomic) ops are expensive. > > _______________________________________________ > freebsd-current@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-current > To unsubscribe, send any mail to "freebsd-current-unsubscribe@freebsd.org"
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