[OpenAFS-devel] LWP and clang

[Benjamin Kaduk]

On Wed, 16 Oct 2013, Marc Dionne wrote:

> On Wed, Oct 16, 2013 at 2:00 PM, Benjamin Kaduk <kaduk@mit.edu> wrote:
>> On Wed, 16 Oct 2013, Marc Dionne wrote:
>>
>>> On Wed, Oct 16, 2013 at 1:26 PM, Benjamin Kaduk <kaduk@mit.edu> wrote:
>>>>
>>>> Hi all,
>>>>
>>>> I've been seeing lots of runtime crashes when running clang-compiled
>>>> LWP-using binaries, for several months now at least.  My experiences have
>>>
>>>
>>> Anything interesting about where the crashes occur - in the lwp
>>> functions themselves (savecontext, etc.) ?  and does it crash every
>>> time it is switching lwps or are these sporadic?
>>
>>
>> I only remember crashes that reliably occur at program startup, perhaps even
>> before switching LWPs.
>>
>> Hmm, the example I have handy (aklog.core from ~tip-of-1.6.x) shows the
>> faulting line of source as:
>> rx_lwp.c:174:
>> 174     char name[MAXTHREADNAMELENGTH] = "srv_0";
>
> Crashing here which is probably the first write into stack memory
> after starting the rx_ListenerProc LWP, so that would seem consistent
> with having a bogus stack pointer after switching lwps.

I can access memory at $rsp at the faulting instruction, but it seems to 
only be 8-byte aligned, which may be the issue.  (This is on amd64.)

I will look around a bit more.

-Ben

P.S. I looked at Chas's suggestion of src/lwp/rw, but it doesn't link, 
finding no main().