On Fri, Apr 8, 2016 at 3:15 AM, Johannes Berg <johan...@sipsolutions.net> wrote:
> On Fri, 2016-04-08 at 09:01 +0200, Johannes Berg wrote:
>> On Fri, 2016-04-08 at 08:56 +0200, Johannes Berg wrote:
>> > On Thu, 2016-04-07 at 21:32 -0400, Avery Pennarun wrote:
>> > > Yes.  Here it is:
>> > > http://apenwarr.ca/tmp/mac80211-agg-status-crash.ko
>> > >
>> > Unfortunately there are no debug symbols in this file, so it
>> > doesn't
>> > help me much. I can't even seem to get objdump to disassemble it
>> > correctly: looks like the file is in thumb, going from things
>> > like R_ARM_THM_CALL relocations, but even -Mforce-thumb doesn't
>> > seem
>> > to DRT; sta_agg_status_read+0xeb isn't even a valid instruction
>> > offset in regular ARM mode.
>> >
>> It *seems* that it most likely crashes on the first access to tid_tx,
>> which is consistent with the story of disabling TX aggregation
>> timeouts
>> reducing the chances.
>>
>> So I guess we have to look for some TX aggregation teardown RCU
>> pointer problem?
>
> Can't find anything. The only other thing I saw now is that the TID
> appears to be 7 (in r7), might be worth looking for whether that's a
> common thing or not?

Just to be clear, this crash is only from *reading* the agg_status
files.  I don't know if the crashiness reduces when disabling the
aggregation timeouts, since that's a separate bug (in which the queue
gets stuck and the 'pending' column of this file just keeps
increasing).

I'll try twiddling some options again tomorrow and see if I can get
one with proper debug symbols.  For what it's worth, this platform is
"ARMv7 Processor rev 1 (v7l)" and the gcc build is made for Cortex A9.
You can find an x86 build of our toolchain in the git repo at
https://gfiber.googlesource.com/toolchains/mindspeed.

Thanks for looking into it :)

Avery
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