[Cbe-oss-dev] Potential issue with spu_stop in loop

[Kazunori Asayama]

malc wrote:
> Following up my own thread - I failed to note that the o/p has a ppu
> side context_create with SPE_EVENTS_ENABLE - but no event handler
> registered to consume them, creating the context without this mask,
> the original code works fine...
 >
 > malc.

We discussed this issue before. See the thread below:

     http://ozlabs.org/pipermail/cbe-oss-dev/2008-March/004355.html

I have alternative idea to solve this problem. I'll submit an
experimental patch to this ML later.

> 
> On Tue, Jun 3, 2008 at 12:58 AM, malc <mlashley at gmail.com> wrote:
>> Running the test code against a libspe2 built with debug symbols - it
>> blocks on a pipe-write here:
>>
>> #1  0x00000400000575a4 in _event_spe_context_run (spe=0x10014010,
>> entry=0xfffffd05f54, runflags=0, argp=0x0, envp=0x0,
>>    stopinfo=0xfffffd05f58) at spe_event.c:489
>> 489       if (write(evctx->stop_event_pipe[1], stopinfo,
>> sizeof(*stopinfo)) != sizeof(*stopinfo)) {
>> 490       /* error check. */
>> 491       }
>>
>> I have proved this to be the case, a simple 'cat /proc/<pid>/fd/7'
>> will allow the test-application to run to completion each time.
>>
>> It tallies - since kernel 2.6.11 or so pipe size has been 64K - test
>> app bails at around 2720, sizeof(*stopinfo) is 24 bytes, giving us
>> 65xxx or thereabouts.
>>
>> In _event_spe_context_initialize - we make the read-side of the pipe
>> non-blocking, but not the write side. Given the comment about error
>> check above - I guess the author intended to set the write-side
>> likewise. I did this - and the test-app runs to completion.
>>
>> I'd submit a patch - but I still can't see what's *consuming* the
>> stopinfo at the read-side of the pipe - breakpoint @
>> _event_spe_stop_info_read() doesn't get hit... and also I can't
>> explain why this isn't hit on the QS21 blades (as reported in the
>> developerworks thread)
>>
>> Cheers,
>> malc.
>>
>>
>>
>>
>>
>> On Mon, Jun 2, 2008 at 10:21 PM, Goffredo Marocchi <panajev at gmail.com> wrote:
>>> http://www-128.ibm.com/developerworks/forums/thread.jspa?threadID=205730&tstart=0
>>>
>>> It only seems to be a problem for PS3 and not for Cell Blades: it fails on
>>> the thread starter's PS3 Linux set-up as it fails on mine, but works
>>> flawlessly on the two Cell Blades other users tested that code on.
>>>
>>> The code is available as an attachment to the second post:
>>>
>>> http://www-128.ibm.com/developerworks/forums/servlet/JiveServlet/download/739-205730-14088270-322870/spu_stop_ex.tar.gz
>>>
>>> Could it be a PS3 Linux kernel related issue ?

-- 
(ASAYAMA Kazunori
   (asayama at sm.sony.co.jp))
t