svn commit: r269127 - head/sys/dev/usb/wlan

[Hans Petter Selasky]

On 07/27/14 02:10, Adrian Chadd wrote:
> On 26 July 2014 12:13, Hans Petter Selasky <hps at selasky.org> wrote:
>> On 07/26/14 20:36, Adrian Chadd wrote:
>>>
>>> Hi,
>>>
>>> We should likely review how the PLCP bits are being used and why it's
>>> getting a rate of 0 in the first place.
>>>
>>> So, why's it getting a rate of 0 passed into the transmit path?
>>>
>>>
>>
>> Hi Adrian,
>>
>> Here is the backtrace of the panic:
>>
>> Fatal trap 18: integer divide fault while in kernel mode
>> cpuid = 2; apic id = 02
>> instruction pointer     = 0x20:0xffffffff807826cf
>> stack pointer           = 0x28:0xffffff8000305090
>> frame pointer           = 0x28:0xffffff80003050a0
>> code segment            = base 0x0, limit 0xfffff, type 0x1b
>>                          = DPL 0, pres 1, long 1, def32 0, gran 1
>> processor eflags        = interrupt enabled, resume, IOPL = 0
>> current process         = 15 (usbus0)
>> trap number             = 18
>> panic: integer divide fault
>> cpuid = 2
>> KDB: stack backtrace:
>> #0 0xffffffff809257e6 at kdb_backtrace+0x66
>> #1 0xffffffff808eb3ae at panic+0x1ce
>> #2 0xffffffff80cd2c30 at trap_fatal+0x290
>> #3 0xffffffff80cd3480 at trap+0x250
>> #4 0xffffffff80cbc783 at calltrap+0x8
>> #5 0xffffffff80783d90 at ural_start+0x1d0
>> #6 0xffffffff809aa2ea at if_transmit+0xea
>> #7 0xffffffff809ef7b2 at ieee80211_start+0x542
>> #8 0xffffffff809aa2ea at if_transmit+0xea
>> #9 0xffffffff809ae8b3 at ether_output_frame+0x33
>> #10 0xffffffff809aee30 at ether_output+0x530
>> #11 0xffffffff80a186b4 at ip_output+0xd74
>> #12 0xffffffff80a87d2a at tcp_output+0xfea
>> #13 0xffffffff80a82222 at tcp_do_segment+0xc02
>> #14 0xffffffff80a85219 at tcp_input+0xa29
>> #15 0xffffffff80a155fa at ip_input+0xaa
>> #16 0xffffffff809b7808 at netisr_dispatch_src+0x218
>> #17 0xffffffff809ae3fd at ether_demux+0x14d
>
> Hm, so at some point that rate was not assigned to something. Can you
> trace the ural_start path to see where it's supposed to be calculating
> the rate?
>

Rate comes from this:

         tp = &vap->iv_txparms[ieee80211_chan2mode(ni->ni_chan)];
         if (IEEE80211_IS_MULTICAST(wh->i_addr1))
                 rate = tp->mcastrate;
         else if (tp->ucastrate != IEEE80211_FIXED_RATE_NONE)
                 rate = tp->ucastrate;
         else
                 rate = ni->ni_txrate;

--HPS