Re: [PATCH] ACPI : Avoid bogus timeout about SMbus check

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On Thursday 04 of September 2008 at 14:18:20, Andi Kleen wrote:
> On Tue, Aug 26, 2008 at 01:57:34PM +0800, Zhao Yakui wrote:
> > Subject: ACPI: Avoid bogus timeout about SMbus check
> >
> > >From :  Zhao Yakui <yakui.zhao@xxxxxxxxx>
> >
> > In the function of wait_transaction_complete when the timeout happens,
> > OS will try to check the status of SMbus again. If the status is what OS
> > expected, it will be regarded as the bogus timeout. Otherwise it will be
> > treated as ETIME.
> >
> > http://bugzilla.kernel.org/show_bug.cgi?id=10483
>
> I added it for 2.6.27 thanks (since it seems to be a regression)

Hi all,

the problem in bug 10483 isn't solved, unfortunately the patch applied to 
2.6.27 isn't the one I tested.

The problem I face is that wait_transaction_complete() in sbshc.c doesn't take 
at most "timeout" time (=one second), but it rather often takes very long 
time to complete on my system (several minutes) - notebook Acer TravelMate 
4502WLMi.

To describe the problem I need to go into wait_event_timeout() macro as used 
in wait_transaction_complete(): it first calls the user method 
smb_check_done() to check if the loop should end and if not, it waits for at 
most "timeout" time. The wait can be woken-up by a wake_up() method and if 
so, it remembers the remaining "timeout", repeats the call to user method 
smb_check_done() and possibly continues with wait (with the 
remaining "timeout"). This is done in a loop.

Now my problem: the wait_event_timeout() loop takes several minutes instead of 
one second (as specified by the parameter "timeout"). The reason for that - as 
I think - is this:

  1. The smb_check_done() method called each loop takes some time to execute, 
but this time is not included into the overall timeout.
  2. The wait_event_timeout() is woken-up by smbus_alarm() very early each 
loop, so the remaining "timeout" gets lower very slow (I think it is so, but 
I haven't verified this hypothesis yet).

So my question is what I shoud do now? If you want to see some logs (and the 
original patch), please go to my bug report:

  http://bugzilla.kernel.org/show_bug.cgi?id=10483

Thanks.

Note: I'm building my house after my normal work, so I don't have much time 
left, but I will do my best to try whatever you suggest. And sorry for my 
english :-)

Regards,
Oldrich.

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