RFR: 7131399: Poll system call appears to be broken on Mac OS [macosx]

[Chris Hegarty]

Thanks the explanations. As I said, I'm fine with the change as is.

-Chris.

On 01/24/12 10:41 AM, Michael McMahon wrote:
> On 24/01/12 10:23, Chris Hegarty wrote:
>> I'm OK with this as it, but here are a few comments:
>>
>> The logic around the initial setting of the timeout seems a little
>> unnecessary (and the additional pointer), but not wrong.
>>
> Chris,
>
> The setting of the timeval could be combined ok, but I wanted to avoid
> calling gettimeofday()
> in the case where timeout == 0
>> The comments should also be updated.
>>
> Yes, I'll do that. It still refers to poll() instead of select() now.
> I'll add a comment about
> the bug too.
>> Given this problem should the build be setting USE_SELECT?
>>
> I thought about that, and decided against it for two reasons.
>
> 1) it's only used by PlainSocketImpl in the networking code, and that
> usage doesn't seem
> to be affected by this problem. poll() is potentially a little more
> efficient than select() also
>
> 2) USE_SELECT is referenced in other places in other native code (in AWT)
> and I don't want to affect those usages. Granted that raises a question
> as to whether they
> are affected by this bug. But, I don't believe they are since, as far as
> I can see UDP sockets
> aren't used there.
>
> - Michael
>
>
>> -Chris.
>>
>> On 01/23/12 10:32 PM, Michael McMahon wrote:
>>> On 23/01/12 21:30, Alan Bateman wrote:
>>>> On 23/01/2012 17:09, Michael McMahon wrote:
>>>>> Can I get the following change reviewed please?
>>>>>
>>>>> http://cr.openjdk.java.net/~michaelm/7131399/webrev.1/
>>>>>
>>>>> The problem is that poll(2) doesn't seem to work in a specific edge
>>>>> case tested by JCK,
>>>>> namely, when a zero length UDP message is sent on a DatagramSocket.
>>>>> The problem is only
>>>>> detected on timed reads, ie. normal blocking reads work fine.
>>>>>
>>>>> The fix is to make the NET_Timeout() function use select() instead of
>>>>> poll().
>>>>>
>>>>> Thanks,
>>>>> Michael.
>>>>>
>>>> The first argument to select is s+1, shouldn't is be 1?
>>>>
>>>> -alan
>>> No, I don't think so. fd_sets are bit masks and you have to specify the
>>> highest numbered bit in the
>>> mask (+1).
>>>
>>> - Michael.
>