Date: Mon, 26 Mar 2001 17:24:39 -0800 (PST) From: John Baldwin <jhb@FreeBSD.org> To: Andrew Gallatin <gallatin@cs.duke.edu> Cc: alpha@FreeBSD.org, obrien@FreeBSD.org Subject: Re: dump(8) Message-ID: <XFMail.010326172439.jhb@FreeBSD.org> In-Reply-To: <15039.59182.857539.804159@grasshopper.cs.duke.edu>
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On 27-Mar-01 Andrew Gallatin wrote:
>
> David O'Brien writes:
> > This broken dump(8) situation *must* get fixed. It is time to back out
> > commits. Does anyone have any idea what commit(s) broke dump?
>
> Nope.
>
> Its almost certainly related to the linuxthreads problem I was talking
> about last week where a userland app dies on an instruction fault
> with a PC somwhere in witness_exit().
>
> I haven't been able to figure it out yet..
Try turning preemption off (i.e. remove it from the kernel config). On the x86
side we've seen that non-preemption safe code can blow up in very bad ways. :(
FWIW, I've tracked down the vfs_object_create() panic some more after adding in
printf's to VOP_CREATEVOBJECT() as so:
static __inline int VOP_CREATEVOBJECT(
struct vnode *vp,
struct ucred *cred,
struct proc *p)
{
struct vop_createvobject_args a;
int rc;
a.a_desc = VDESC(vop_createvobject);
a.a_vp = vp;
a.a_cred = cred;
a.a_p = p;
printf("%s: a = %p, a.a_desc = %p\n", __func__, &a, a.a_desc);
printf("vnop %s, offset %d, flags = %d\n", a.a_desc->vdesc_name,
a.a_desc->vdesc_offset, a.a_desc->vdesc_flags);
printf("vp->v_op = %p, VOFFSET(vop_createvobject) = %d\n", vp->v_op,
VOFFSET(vop_createvobject));
printf("vnop to call = %p\n", vp->v_op[VOFFSET(vop_createvobject)]);
rc = VCALL(vp, VOFFSET(vop_createvobject), &a);
return (rc);
}
I get the following output prior to the panic:
VOP_CREATEVOBJECT: a = 0xfffffe000917da88, a.a_desc = 0xfffffc00006421c0
vnop vop_createvobject, offset 44, flags = 0
vp->v_op = 0xfffffe00006e7600, VOFFSET(vop_createvobject) = 44
vnop to call = 0xfffffc0000541d80
VOP_CREATEVOBJECT: a = 0xfffffe000917d8a8, a.a_desc = 0xfffffc00006421c0
vnop vop_createvobject, offset 44, flags = 0
vp->v_op = 0xfffffe00006e7600, VOFFSET(vop_createvobject) = 44
vnop to call = 0xfffffc0000541d80
VOP_CREATEVOBJECT: a = 0xfffffe000917d788, a.a_desc = 0xfffffc00006421c0
vnop vop_createvobject, offset 44, flags = 0
vp->v_op = 0xfffffe00006e7600, VOFFSET(vop_createvobject) = 44
vnop to call = 0xfffffc0000541d80
VOP_CREATEVOBJECT: a = 0xfffffe000917da28, a.a_desc = 0xfffffc00006421c0
vnop vop_createvobject, offset 44, flags = 0
vp->v_op = 0x8441fd6f7a07947c, VOFFSET(vop_createvobject) = 44
fatal kernel trap:
trap entry = 0x4 (unaligned access fault)
a0 = 0x8441fd6f7a07947c
a1 = 0x29
a2 = 0x11
etc.
So it looks like the pointer to the vop function table is getting spammed.
I'm not sure if the whole vp is spammed or not. :(
> Drew
--
John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
PGP Key: http://www.baldwin.cx/~john/pgpkey.asc
"Power Users Use the Power to Serve!" - http://www.FreeBSD.org/
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