[Mono-dev] ConcurrentStack with value type in 2.10

[Yuriy Solodkyy]

Hi All,

I just check this on fresh build mono from master.

It is not the problem that you can see on each run.  You need to run
on 8-cores to observe it frequently enough.
My environment is Linux x64 (tried: ubuntu 10, ubuntu 12, opensuse 12).

Typically if you start test app and it does not crash it will not crash later.

However, I just got it again, the stack trace is below.  This is just
a different favor of the same problem.  Sometimes ConcurrentStack
returns inconsistent data, sometimes it crashes.
See the code sample at

https://github.com/ysw/mono-socket-problem/tree/master/ConcurrentTest



ubuntu at ip-10-244-0-134:~/mono-socket-problem/ConcurrentTest/bin/Debug$
m CocurrentTest.exe
Hello World!

Unhandled Exception:
mono() [0x49545d]
mono() [0x497079]
mono() [0x49918b]
mono() [0x4f0e67]
[0x4199f9ac]

[ERROR] FATAL UNHANDLED EXCEPTION: System.IndexOutOfRangeException:
Array index is out of range.
  at (wrapper stelemref) object:virt_stelemref_class (intptr,object)
  at System.Collections.Concurrent.ObjectPool`1[T].Release
(System.Collections.Concurrent.T obj) [0x00000] in <filename
unknown>:0
  at System.Collections.Concurrent.ConcurrentStack`1[CocurrentTest.MainClass+Data].TryPop
(CocurrentTest.Data& result) [0x00000] in <filename unknown>:0
  at CocurrentTest.MainClass+<Main>c__AnonStorey0.<>m__0
(System.Object v) [0x00000] in <filename unknown>:0
  at System.Threading.Thread.StartInternal () [0x00000] in <filename unknown>:0
ubuntu at ip-10-244-0-134:~/mono-socket-problem/ConcurrentTest/bin/Debug$



Updating https://bugzilla.xamarin.com/show_bug.cgi?id=6229 as well

--yuriy


On Mon, Jul 23, 2012 at 3:45 PM, Alan <alan.mcgovern at gmail.com> wrote:
> I cannot reproduce the problem either. What exact version of 2.10 did
> you test against? It's possible the bug has already been fixed in a
> newer release of the 2.10 series.
>
> Alan
>
> On 23 July 2012 13:32, Rodrigo Kumpera <kumpera at gmail.com> wrote:
>> Hi Yuriy,
>>
>> With how many cores and on what CPU did managed to reproduce this?
>> I'm running this on my 4 cores nehalem mac without any luck. I'll diff
>> ConcurrentStack
>> between 2.8 and 2.10 to see what could be.
>>
>> On Sun, Jul 22, 2012 at 5:10 AM, Yuriy Solodkyy <yuriy at couldbedone.com>
>> wrote:
>>>
>>> Hi,
>>>
>>> It looks like the ConcurrentStack does not work with big enough
>>> structures anymore.  12 bytes struct is enough to reproduce the
>>> problem occasionally, 16 bytes structure to reproduce it immediately.
>>> It worked fine in mono 2.8.  The following code shows that we may pop
>>> inconsistent structure from the stack from time to time.
>>>
>>> using System;
>>> using System.Collections.Concurrent;
>>> namespace CocurrentTest {
>>>         class MainClass {
>>>                 struct Data {
>>>                         public int A; public int B; public int C; public
>>> int D;
>>>                         public Data(int v) {
>>>                                 A = v; B = -v; C = v; D = -v;
>>>                         }
>>>                 }
>>>
>>>                 public static void Main (string[] args) {
>>>                         Console.WriteLine ("Hello World!");
>>>                         var data = new byte[1024 * 1024];
>>>                         var stack = new ConcurrentStack<Data> ();
>>>
>>>                         for (var i = 0; i < 50; i++) {
>>>
>>>                                 var thread = new System.Threading.Thread
>>> (v => {
>>>
>>>                                         var rnd = new Random ();
>>>                                         while (true) {
>>>                                                 int pushCount = rnd.Next
>>> (50);
>>>                                                 int popCount = rnd.Next
>>> (50);
>>>
>>>                                                 for (var k = 0; k <
>>> pushCount; k++) {
>>>
>>>
>>>                                                         var sample =
>>> new Data (rnd.Next(Int32.MaxValue));
>>>                                                         CheckSample
>>> (sample);
>>>
>>>                                                         stack.Push
>>> (sample);
>>>                                                 }
>>>
>>>                                                 for (var k = 0; k <
>>> popCount; k++) {
>>>                                                         Data
>>> retrievedSample = new Data();
>>>                                                         if
>>> (stack.TryPop (out retrievedSample)) {
>>>
>>> CheckSample (retrievedSample);
>>>                                                         }
>>>                                                 }
>>>                                         }
>>>                                 }
>>>                                 );
>>>
>>>                                 thread.Start ();
>>>                         }
>>>                 }
>>>
>>>                 static void CheckSample (Data sample){
>>>                         if (sample.A != -sample.B || sample.A !=
>>> sample.C || sample.B != sample.D)
>>>                                 throw new Exception (string.Format
>>> ("Invalid sample detected"));
>>>                 }
>>>         }
>>> }
>>>
>>>
>>> --
>>> Yuriy Solodkyy
>>> _______________________________________________
>>> Mono-devel-list mailing list
>>> Mono-devel-list at lists.ximian.com
>>> http://lists.ximian.com/mailman/listinfo/mono-devel-list
>>
>>
>>
>> _______________________________________________
>> Mono-devel-list mailing list
>> Mono-devel-list at lists.ximian.com
>> http://lists.ximian.com/mailman/listinfo/mono-devel-list
>>



-- 
Yuriy Solodkyy
(y.solodkyy at gmail.com)