On Mon, 15 Mar 1999, Dmitrij Tejblum wrote:

> Matthew Dillon wrote:
> > 
> >     We'll get a quick fix committed but the lockmgr stuff needs a real
> >     going-over... having interrupts using the general lockmgr call is
> >     a disaster waiting to happen.
> 
> Hmmm. After I looked a bit further, it looks like a bug in the 
> scheduler (?). Here is the stack trace:
> 
> #9  0xc01ff64e in trap (frame={tf_es = 16, tf_ds = 16, tf_edi = 0, 
>       tf_esi = 16777216, tf_ebp = -999002708, tf_isp = -999002744, 
>       tf_ebx = -1071228500, tf_edx = -2, tf_ecx = 0, tf_eax = 0, 
>       tf_trapno = 12, tf_err = 0, tf_eip = -1072584332, tf_cs = 8, 
>       tf_eflags = 66050, tf_esp = -999002524, tf_ss = -1071228500})
>     at ../../i386/i386/trap.c:438
> #10 0xc011a974 in lockmgr (lkp=0xc02659ac, flags=1, interlkp=0x0, p=0x0)
>     at ../../kern/kern_lock.c:217
> #11 0xc01d8c5b in vm_map_lookup (var_map=0xc4746e64, vaddr=3294351360, 
>     fault_typea=1 '\001', out_entry=0xc4746e68, object=0xc4746e5c, 
>     pindex=0xc4746e60, out_prot=0xc4746e4b "?\a", wired=0xc4746e44)
>     at ../../vm/vm_map.c:2463
> #12 0xc01d4153 in vm_fault (map=0xc02659ac, vaddr=3294351360, 
>     fault_type=1 '\001', fault_flags=0) at ../../vm/vm_fault.c:197
> #13 0xc01ff9ac in trap_pfault (frame=0xc4746f18, usermode=0, eva=3294351360)
>     at ../../i386/i386/trap.c:825
> #14 0xc01ff64e in trap (frame={tf_es = 16, tf_ds = 16, tf_edi = 46137344, 
>       tf_esi = -1071149988, tf_ebp = -999002244, tf_isp = -999002304, 
>       tf_ebx = 18341888, tf_edx = -1000615936, tf_ecx = -1005747008, 
>       tf_eax = 0, tf_trapno = 12, tf_err = 0, tf_eip = -1071650796, tf_cs = 
> 8, 
>       tf_eflags = 65606, tf_esp = -1072552121, tf_ss = -999654400})
>     at ../../i386/i386/trap.c:438
> #15 0xc01fe814 in swtch_com ()
> #16 0xc01ff859 in trap (frame={tf_es = 47, tf_ds = 47, tf_edi = 20, 
>       tf_esi = 136019608, tf_ebp = -1077948228, tf_isp = -999002156, 
>       tf_ebx = 307, tf_edx = 136220264, tf_ecx = 136630944, 
>       tf_eax = 135716928, tf_trapno = 7, tf_err = 0, tf_eip = 134536416, 
>       tf_cs = 31, tf_eflags = 514, tf_esp = -1077948244, tf_ss = 47})
>     at ../../i386/i386/trap.c:195
> #17 0xc01f5aa3 in swi_ast_user ()
> 
> the trap in swtch_com() (frame #15) is here:
>         /* switch address space */            <----- line 622
>         movl    %cr3,%ebx
>         cmpl    PCB_CR3(%edx),%ebx            <----- trap
>         je              4f
> 
> I don't think this line is supposed to cause a trap...

When it says "switch address space" What exactly do you think it's going to
do? What I mean is, I'm pretty certain this is a good trap =)

The real problem did seem to be the NULL p dereference, as it was obvious
that it could happen in the code.

> 
> Dima
> 
> 
> 
> 
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 Brian Feldman                                    _ __  ___ ___ ___  
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