Re: LoR aironet/VM subsystem

Alan Cox wrote:
> On Wed, Aug 11, 2004 at 10:37:42PM -0700, Nate Lawson wrote:
> 
>>an0: <Cisco Systems 340 Series Wireless LAN Adapter> at port 
>>0x2000-0x203f irq 11 function 0 config 5 on pccard1
>>an0: got RSSI <-> dBM map
>>an0: supported rates: 1Mbps 2Mbps 5.5Mbps 11Mbps
>>an0: Ethernet address: 00:40:96:42:91:c5
>>an0: [GIANT-LOCKED]
>>lock order reversal
>> 1st 0xc163339c an0 (network driver) _at_ dev/an/if_an.c:1931
>> 2nd 0xc134b164 user map (user map) _at_ vm/vm_map.c:2902
>>KDB: stack backtrace:
>>kdb_backtrace(0,ffffffff,c0696d88,c0697a08,c066630c) at kdb_backtrace+0x29
>>witness_checkorder(c134b164,9,c06469a0,b56) at witness_checkorder+0x544
>>_sx_xlock(c134b164,c0646997,b56) at _sx_xlock+0x50
>>_vm_map_lock_read(c134b128,c0646997,b56,1b69978,c1402e4c) at 
>>_vm_map_lock_read+0x33
>>vm_map_lookup(d0b69a10,bfbfd000,1,d0b69a14,d0b69a04) at vm_map_lookup+0x28
>>vm_fault(c134b128,bfbfd000,1,0,c1371840) at vm_fault+0x66
>>trap_pfault(d0b69ad8,0,bfbfd000) at trap_pfault+0xd2
>>trap(c04f0018,c06b0010,c1630010,c1633df4,bfbfd000) at trap+0x311
>>calltrap() at calltrap+0x5
>>--- trap 0xc, eip = 0xc060661e, esp = 0xd0b69b18, ebp = 0xd0b69ba4 ---
>>generic_copyin(c1632000,c020693a,d0b69c60,c04d4b78,c06bb8e0) at 
>>generic_copyin+0x32
>>ifhwioctl(c020693a,c1632000,d0b69c60,c1371840,c0698048) at ifhwioctl+0x854
>>ifioctl(c16219e0,c020693a,d0b69c60,c1371840,0) at ifioctl+0xbd
>>soo_ioctl(c158f440,c020693a,d0b69c60,c133c480,c1371840) at soo_ioctl+0x2b1
>>ioctl(c1371840,d0b69d14,3,2,292) at ioctl+0x3e0
>>syscall(2f,2f,2f,3,bfbfef64) at syscall+0x217
>>Xint0x80_syscall() at Xint0x80_syscall+0x1f
>>--- syscall (54, FreeBSD ELF32, ioctl), eip = 0x280d0083, esp = 
>>0xbfbfad7c, ebp = 0xbfbfadb8 ---
>>
> 
> This looks like a programming error in the driver.  Specifically,
> the driver is calling copyin() while holding a mutex.  That's not
> allowed because of the potential for a page fault that sleeps.

It is.  AN_LOCK is held over the entire contents of an_ioctl().  This 
function is so huge, it's unclear how to reduce the scope of this lock.

-Nate