page fault in sched_pin()

Don Lewis truckman at FreeBSD.org
Sat Sep 11 03:00:07 PDT 2004


I just cvsup'ed a few hours ago and I'm getting a page fault in
sched_pin() early in the boot process.  It looks like a NULL pointer
dereference.  I'm using SCHED_4BSD+PREEMPTION.

It looks like the problem is that proc0_init() (which calls schedinit())
needs to be called before kmeminit(), so that the thread0->td_sched is
initialized before it is dereferenced in sched_pin().

The SYSINIT for kmeminit() is SI_SUB_KMEM, which is defined as
0x1800000, while the SYSINIT for proc0_init() is SI_SUB_INTRINSIC, which
is defined as 0x2200000.

An alternative would be to make sched_pin() a no-op this early in the
boot process.


Copyright (c) 1992-2004 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
        The Regents of the University of California. All rights reserved.
FreeBSD 6.0-CURRENT #241: Sat Sep 11 02:23:16 PDT 2004
    dl at scratch.catspoiler.org:/usr/obj/usr/src/sys/GENERICSMB
WARNING: WITNESS option enabled, expect reduced performance.
kernel trap 12 with interrupts disabled


Fatal trap 12: page fault while in kernel mode
cpuid = 0; apic id = 00
fault virtual address   = 0x30
fault code              = supervisor write, page not present
instruction pointer     = 0x8:0xc0620c47
stack pointer           = 0x10:0xc0c21cc0
frame pointer           = 0x10:0xc0c21cc0
code segment            = base 0x0, limit 0xfffff, type 0x1b
                        = DPL 0, pres 1, def32 1, gran 1
processor eflags        = resume, IOPL = 0
current process         = 0 ()
[thread 0]
Stopped at      sched_pin+0xf:  incl    0x30(%eax)
db> tr
sched_pin(c0c21cdc,c07a0edc,c1047828,bfeff000,c103a000) at sched_pin+0xf
pmap_zero_page(c1047828,bfeff000,c103a000,c0c21cf4,c075f724) at pmap_zero_page+0x35
pmap_growkernel(d6247000) at pmap_growkernel+0xf4
vm_map_findspace(c103a000,bfeff000,14000000,c08d3c3c) at vm_map_findspace+0x118
vm_map_find(c103a000,0,0,0,c08d3c3c,14000000,1,7,7,0) at vm_map_find+0x41
kmem_suballoc(c103a000,c08d3c3c,c08d3c40,14000000,14000) at kmem_suballoc+0x36
kmeminit(0,c1ec00,c1e000,0,c0440b85) at kmeminit+0xe5
mi_startup() at mi_startup+0x96
begin() at begin+0x2c
db> 



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