Date: Sun, 18 Oct 2009 21:22:36 -0700 From: Julian Elischer <julian@elischer.org> To: Harsha <inpcb.harsha@gmail.com> Cc: freebsd-current@freebsd.org, "Robert N. M. Watson" <rwatson@freebsd.org>, net@freebsd.org Subject: Re: Page fault in IFNET_WLOCK_ASSERT [if.c and pccbb.c] Message-ID: <4ADBE98C.3030404@elischer.org> In-Reply-To: <e1b1c5880910181626g300213afj128bee62f424810a@mail.gmail.com> References: <e1b1c5880910111226o65e0d1a9va975f4cd837271bb@mail.gmail.com> <alpine.BSF.2.00.0910112126050.48605@fledge.watson.org> <e1b1c5880910112138x1b46ff0eo39c10691a978c164@mail.gmail.com> <FE5F0845-B909-4B9B-A999-DAA7D8F4E56D@freebsd.org> <e1b1c5880910172328s6bc0c53ctc782b9993ffbdb00@mail.gmail.com> <4ADAB8E0.3090502@elischer.org> <e1b1c5880910181626g300213afj128bee62f424810a@mail.gmail.com>
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Harsha wrote: > On Sat, Oct 17, 2009 at 11:42 PM, Julian Elischer <julian@elischer.org> wrote: >> Harsha wrote: >>> <rwatson@freebsd.org> wrote: >>>> Looks like a NULL pointer dereference, so perhaps a more traditional bug >>>> -- >>>> could you convert ifindex_alloc_locked+0x71 to a line of code? You can do >>>> this using kgdb on the kernel symbols file, perhaps "l >>>> *ifindex_alloc_locked+0x71". >>> It is the for loop in ifindex_alloc_locked() function- >>> for (idx = 1; idx <= V_if_index; idx++) >>> >>> idx is a local variable, so I figured it is V_if_index is what is >>> causing the page fault. It does look like a NULL pointer reference - I >>> see that V_if_index comes from that vnet instance's value and uses >>> the macro VNET_VNET_PTR() down the chain. Since the call chain is >>> coming from a new thread cbb_event_thread, I believe that this >>> thread's vnet context needs to be set using CURVNET_SET(). >> but only if you have options VIMAGE defined. if not then CURVNET_SET() >> is a NOP > I do have the VIMAGE options turned on. > > Can someone tell me what is the right way to add the vnet context to > cbb_event_thread? have you read the vimage porting document at: http://p4db.freebsd.org/fileLogView.cgi?FSPC=//depot/projects/vimage/porting_to_vimage.txt > > I tried adding context in two locations- > > 1. In cbb_insert() as- > CURVNET_SET(TD_TO_VNET(curthread)); > > 2. In if_alloc() as- > CURVNET_SET(TD_TO_VNET(curthread)); > > or as > > ifp = malloc(sizeof(struct ifnet), M_IFNET, M_WAITOK|M_ZERO); > #ifdef VIMAGE > ifp->if_vnet = curvnet; > if (ifp->if_home_vnet == NULL) > ifp->if_home_vnet = curvnet; > CURVNET_SET(ifp->if_vnet); > #endif CURVNET_SET sets curvnet but you are using it already, 3 lines above. > > But in all the cases I get a warning/error about unused variable > 'saved_vnet' like this- > > cc1: warnings being treated as errors > /usr/src/sys/net/if.c: In function 'if_alloc': > /usr/src/sys/net/if.c:418: warning: unused variable 'saved_vnet' > > The backtrace is in the link I posted earlier. > > Thanks, > Harsha
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