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Date:      Tue, 13 Feb 2007 13:53:12 -0500
From:      Kris Kennaway <kris@obsecurity.org>
To:        current@FreeBSD.org
Cc:        amd64@FreeBSD.org
Subject:   Page fault in amd64 pmap_qremove from vm_thread_new()
Message-ID:  <20070213185312.GF67616@xor.obsecurity.org>

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--NtwzykIc2mflq5ck
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I get this frequently when running stress2 on an 8-core amd64 system:

Fatal trap 12: page fault while in kernel mode
Fatal trap 12: page fault while in kernel mode


cpuid = 2;


apic id = 02

Fatal trap 12: page fault while in kernel mode

cpuid = 5; fault virtual address        = 0xffff807ffffff040
Fatal trap 12: page fault while in kernel mode
Fatal trap 12: page fault while in kernel mode

cpuid = 4; apic id = 05
apic id = 04
fault virtual address   = 0xffff807ffffff0e0
fault virtual address   = 0xffff807ffffff0b8
cpuid = 0; fault code           = supervisor write data, page not present

instruction pointer     = 0x8:0xffffffff803deedd
cpuid = 3; stack pointer                = 0x10:0xffffffffc7647720
fault code              = supervisor write data, page not present

instruction pointer     = 0x8:0xffffffff803deedd
apic id = 00
stack pointer           = 0x10:0xffffffffcfd7e720
fault code              = supervisor write data, page not present
frame pointer           = 0x10:0xffffffffc7647730
frame pointer           = 0x10:0xffffffffcfd7e730
Fatal trap 12: page fault while in kernel mode

cpuid = 6;
instruction pointer     = 0x8:0xffffffff803deedd

stack pointer           = 0x10:0xffffffffb2b93720

frame pointer           = 0x10:0xffffffffb2b93730

code segment            = base 0x0, limit 0xfffff, type 0x1b

                        = DPL 0, pres 1, long 1, def32 0, gran 1

processor eflags        =
interrupt enabled,
resume, Fatal trap 12: page fault while in kernel mode
apic id = 06
cpuid = 7; fault virtual address        = 0xffff807ffffff108
apic id = 07
fault code              = supervisor write data, page not present
code segment            = base 0x0, limit 0xfffff, type 0x1b
apic id = 03
                        = DPL 0, pres 1, long 1, def32 0, gran 1
fault virtual address   = 0xffff807ffffff068
IOPL = 0
fault code              = supervisor write data, page not present
fault virtual address   = 0xffff807ffffff018
instruction pointer     = 0x8:0xffffffff803deedd
instruction pointer     = 0x8:0xffffffff803deedd
Fatal trap 12: page fault while in kernel mode
stack pointer           = 0x10:0xffffffffbf901720
cpuid = 4; stack pointer                = 0x10:0xffffffffb1c11720
processor eflags        = frame pointer         = 0x10:0xffffffffb1c11730
interrupt enabled, resume, fault code           = supervisor write data, page not present
IOPL = 0
instruction pointer     = 0x8:0xffffffff803deedd
current process         = stack pointer         = 0x10:0xffffffffd5b25720
frame pointer           = 0x10:0xffffffffbf901730
frame pointer           = 0x10:0xffffffffd5b25730
code segment            = base 0x0, limit 0xfffff, type 0x1b
current process         =                       = DPL 0, pres 1, long 1, def32 0, gran 1
code segment            = base 0x0, limit 0xfffff, type 0x1b
code segment            = base 0x0, limit 0xfffff, type 0x1b
18747 (thr2)
[thread pid 18747 tid 142909 ]
Stopped at      pmap_qremove+0x2d:      movq    $0,(%rcx,%rax,8)
db> wh
Tracing pid 18747 tid 142909 td 0xffffff0095710cd0
pmap_qremove() at pmap_qremove+0x2d
vm_thread_new() at vm_thread_new+0x8d
thread_init() at thread_init+0x16
slab_zalloc() at slab_zalloc+0x282
uma_zone_slab() at uma_zone_slab+0x1ae
uma_zalloc_bucket() at uma_zalloc_bucket+0x19d
uma_zalloc_arg() at uma_zalloc_arg+0x3a3
thread_alloc() at thread_alloc+0x1f
create_thread() at create_thread+0xc5
kern_thr_new() at kern_thr_new+0x75
thr_new() at thr_new+0x62
syscall() at syscall+0x310
Xfast_syscall() at Xfast_syscall+0xab
--- syscall (455, FreeBSD ELF64, thr_new), rip = 0x8007a1cac, rsp = 0x7fffffffdef8, rbp = 0 ---
db> show allpcpu
Current CPU: 2

cpuid        = 0
curthread    = 0xffffff00717e8290: pid 18944 "thr2"
curpcb       = 0xffffffffe2e33d50
fpcurthread  = none
idlethread   = 0xffffff00b9aa6520: pid 17 "idle: cpu0"
spin locks held:

cpuid        = 1
curthread    = 0xffffff0015e9d7b0: pid 18736 "thr2"
curpcb       = 0xffffffffbceefd50
fpcurthread  = none
idlethread   = 0xffffff00b9aa6290: pid 16 "idle: cpu1"
spin locks held:
exclusive spin mutex sio r = 0 (0xffffffff806bf3c0) locked @ dev/sio/sio.c:1390

cpuid        = 2
curthread    = 0xffffff0095710cd0: pid 18747 "thr2"
curpcb       = 0xffffffffcfd7ed50
fpcurthread  = none
idlethread   = 0xffffff00b9aa6000: pid 15 "idle: cpu2"
spin locks held:

cpuid        = 3
curthread    = 0xffffff00ad485290: pid 18743 "thr2"
curpcb       = 0xffffffffd5b25d50
fpcurthread  = none
idlethread   = 0xffffff00b9a63cd0: pid 14 "idle: cpu3"
spin locks held:

cpuid        = 4
curthread    = 0xffffff0098fc7000: pid 18942 "thr2"
curpcb       = 0xffffffffc77fad50
fpcurthread  = none
idlethread   = 0xffffff00b9a63000: pid 13 "idle: cpu4"
spin locks held:
exclusive spin mutex turnstile chain r = 0 (0xffffffff80613ed8) locked @ kern/subr_turnstile.c:489

cpuid        = 5
curthread    = 0xffffff00215b8cd0: pid 18708 "thr2"
curpcb       = 0xffffffffb2b93d50
fpcurthread  = none
idlethread   = 0xffffff00b9a8fcd0: pid 12 "idle: cpu5"
spin locks held:

cpuid        = 6
curthread    = 0xffffff005b72d520: pid 18718 "thr2"
curpcb       = 0xffffffffb1c11d50
fpcurthread  = none
idlethread   = 0xffffff00b9a8fa40: pid 11 "idle: cpu6"
spin locks held:

cpuid        = 7
curthread    = 0xffffff0078aae7b0: pid 18782 "thr2"
curpcb       = 0xffffffffbf901d50
fpcurthread  = none
idlethread   = 0xffffff00b9a8f7b0: pid 10 "idle: cpu7"
spin locks held:

For some reason ddb doesn't give sensible backtraces for the running threads:

db> wh 18944
Tracing pid 18944 tid 130433 td 0xffffff009daa7290
fork_trampoline() at fork_trampoline
db> wh 18736
Tracing pid 18736 tid 165977 td 0xffffff00632b2cd0
fork_trampoline() at fork_trampoline
db> wh 18747
Tracing pid 18747 tid 165890 td 0xffffff0037403000
fork_trampoline() at fork_trampoline
db> wh 18743
Tracing pid 18743 tid 165929 td 0xffffff004f59e000
fork_trampoline() at fork_trampoline
db> wh 18942
Tracing pid 18942 tid 130531 td 0xffffff000a166520
fork_trampoline() at fork_trampoline
db> wh 18708
Tracing pid 18708 tid 166269 td 0xffffff005c28a290
fork_trampoline() at fork_trampoline
db> wh 18718
Tracing pid 18718 tid 111088 td 0xffffff0081f51a40
fork_trampoline() at fork_trampoline
db> wh 18782
Tracing pid 18782 tid 166078 td 0xffffff0052b4c000
fork_trampoline() at fork_trampoline

Kris



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