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On Dec 13, 2003, at 5:59 PM, Simon Burge wrote:

Thus spake David Laight:

>> If it can sleep while traversing the process list, then the process
>> it is referencing can exit and the pointer becomes invalid.
>> Which would mean that it can't use allprocs to act on all processes.

Uh, doesn't this ktrace path always operate on the current process?  
How could the current process exit in this case?

> Here's some traces from a panic:
>
> panic: spinlock_switchcheck: CPU 0 has 1 spin locks
> Stopped in pid 11368.1 (ktrace) at      netbsd:cpu_Debugger+0x4:       
>  leave
>
> db{0}> tr
> cpu_Debugger(c07dfa20,c06dd8f5,36d,1,0) at netbsd:cpu_Debugger+0x4
> panic(c072c200,0,1,c0784920,e8763800) at netbsd:panic+0x121
> spinlock_switchcheck(c,1,f0d4b8dc,c036097d,c07798d4) at 
> netbsd:spinlock_switchcheck+0x7b
> mi_switch(e8763800,0,1ca,c45fcecc,6) at netbsd:mi_switch+0x6c
> ltsleep(c45fcea4,11,c06df5cc,0,c45fcecc) at netbsd:ltsleep+0x4b3
> biowait(c45fcea4,f0d4b9d0,595,cb535000,eafa612c) at netbsd:biowait+0xeb
> genfs_gop_write(eafa612c,f0d4ba14,1,0,eafa612c) at 
> netbsd:genfs_gop_write+0x2cc
> genfs_putpages(f0d4bba4,989680,0,eafa612c,c05cdba0) at 
> netbsd:genfs_putpages+0x999
> VOP_PUTPAGES(eafa612c,0,0,2000,0) at netbsd:VOP_PUTPAGES+0x40
> ffs_write(f0d4bcd4,3fd7c853,f0d4bd0c,c03aa710,c05cd260) at 
> netbsd:ffs_write+0x666
> VOP_WRITE(eafa612c,f0d4bd84,37,c4474380,eafa612c) at 
> netbsd:VOP_WRITE+0x34
> vn_write(e82df964,e82df98c,f0d4bd84,c4474380,1) at netbsd:vn_write+0xc0
> ktrwrite(e874e3b4,f0d4bdd4,7,c035ec97,6) at netbsd:ktrwrite+0xd4
> ktremul(e874e3b4,e874e3b4,0,c0779080,0) at netbsd:ktremul+0x4b
> ktrops(e874e3b4,e874e3b4,0,3be,e82df964) at netbsd:ktrops+0xad
> ktrace_common(e874e3b4,0,3be,2c68,e82df964) at 
> netbsd:ktrace_common+0xed
> sys_ktrace(e8763800,f0d4bf64,f0d4bf5c,2d,c06dd8f5) at 
> netbsd:sys_ktrace+0xf1
> syscall_plain(f0d4bfa8,1f,1f,1f,1f) at netbsd:syscall_plain+0x18a
>
> db{0}> mac cpu 6
> using cpu 6
> db{0}> tr
> __cpu_simple_lock(c07798d4,42c1d80,0,c384f8c4,0) at 
> netbsd:__cpu_simple_lock+0x6f
> _simple_lock(c07798d4,c06de25f,2a9,c3780800,400) at 
> netbsd:_simple_lock+0x75
> wakeup(c384f8c4,c06dec2d,428,c384f8e0,c384f8e0) at netbsd:wakeup+0x55
> pipe_write(e82df504,e82df52c,f4174ec4,c366b000,1) at 
> netbsd:pipe_write+0x31f
> dofilewrite(e8adccb4,1,e82df504,804d400,400) at netbsd:dofilewrite+0x85
> sys_write(e6c77d48,f4174f64,f4174f5c,4,c07edbd8) at 
> netbsd:sys_write+0x6f
> syscall_plain(f4174fa8,804001f,804001f,481a001f,bfbf001f) at 
> netbsd:syscall_plain+0x18a
>
> Two almost unrelated comments:
>
>  - Should the ddb prompt change to "db{6}> " after issuing the
>    "machine cpu 6" command?
>
>  - I have never been able to get a crash dump from an MP box.  Anyone
>    _ever_ had this work?
>
> Simon.
> --
> Simon Burge                            <simonb@wasabisystems.com>
> NetBSD Support and Service:         http://www.wasabisystems.com/
>
         -- Jason R. Thorpe <thorpej@wasabisystems.com>


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