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Created September 20, 2012 13:36
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mono concurrent queue
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gistfile1.txt
Here are some tests that show some of the failure modes of concurrent queue (all work in CLR impl)
Unhandled Exception:
System.NullReferenceException: Object reference not set to an instance of an object
at System.Collections.Concurrent.ConcurrentQueue`1[T].TryDequeue (System.Collections.Concurrent.T& result) [0x00000] in <filename unknown>:0
at ConsoleApplication1.Program+<TestMonoConcurrentQueueReference>c__AnonStorey1.<>m__0 (System.Object x) [0x00000] in <filename unknown>:0
at System.Threading.Thread.StartInternal () [0x00000] in <filename unknown>:0
[ERROR] FATAL UNHANDLED EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object
at System.Collections.Concurrent.ConcurrentQueue`1[T].TryDequeue (System.Collections.Concurrent.T& result) [0x00000] in <filename unknown>:0
at ConsoleApplication1.Program+<TestMonoConcurrentQueueReference>c__AnonStorey1.<>m__0 (System.Object x) [0x00000] in <filename unknown>:0
at System.Threading.Thread.StartInternal () [0x00000] in <filename unknown>:0
On my machine (8 cores comes within 5 seconds of running)
private static void TestMonoConcurrentQueueReference()
{
var queue = new ConcurrentQueue<object>();
var waits = new List<AutoResetEvent>();
for (int i = 0; i < 5; i++)
{
int q = i;
waits.Add(new AutoResetEvent(false));
var t = new Thread(x =>
{
for (int j = 0; j < 100000000; j++)
{
if (j % 1000000 == 0) Console.Write(".");
queue.Enqueue(new object());
object item;
if (queue.TryDequeue(out item))
{
}
}
waits[q].Set();
});
t.Start();
}
Console.WriteLine("waiting.");
waits.ForEach(x => x.WaitOne());
Console.WriteLine("done.");
}
I end up in the else {} on try dequeue here don't think I should ever be allowed to (and dont end up there in MS impl)
struct TestStruct
{
public long X;
public long Y;
public TestStruct(long x, long y) : this()
{
X = x;
Y = y;
}
}
private static void TestMonoConcurrentQueueBiggerThanReference()
{
var queue = new ConcurrentQueue<TestStruct>();
var waits = new List<AutoResetEvent>();
for(int i=0;i<5;i++)
{
int q = i;
waits.Add(new AutoResetEvent(false));
var t = new Thread(x =>
{
for(int j=0;j<100000000;j++)
{
if(j% 1000000 == 0) Console.Write(".");
queue.Enqueue(new TestStruct(0x11223344, 0x99887766));
TestStruct item;
if(queue.TryDequeue(out item))
{
if(item.X != 0x11223344) throw new Exception("bad x");
if(item.Y != 0x99887766) throw new Exception("bad y");
} else
{
throw new Exception("unable to read."); <~~~~ should never hit this.
}
}
waits[q].Set();
});
t.Start();
}
Console.WriteLine("waiting.");
waits.ForEach(x => x.WaitOne());
Console.WriteLine("done.");
}
For good measure lets take out the exception in the last about not being able to read when it should be able to (eg comment out the throw)
Unhandled Exception:
System.Exception: bad y
at ConsoleApplication1.Program+<TestMonoConcurrentQueueBiggerThanReference>c__AnonStorey3.<>m__2 (System.Object x) [0x00000] in <filename unknown>:0
at System.Threading.Thread.StartInternal () [0x00000] in <filename unknown>:0
Unhandled Exception:
System.NullReferenceException: Object reference not set to an instance of an object
at System.Collections.Concurrent.ConcurrentQueue`1[ConsoleApplication1.Program+TestStruct].TryDequeue (ConsoleApplication1.TestStruct& result) [0x00000] in <filename unknown>:0
at ConsoleApplication1.Program+<TestMonoConcurrentQueueBiggerThanReference>c__AnonStorey3.<>m__2 (System.Object x) [0x00000] in <filename unknown>:0
at System.Threading.Thread.StartInternal () [0x00000] in <filename unknown>:0
Unhandled Exception:
System.NullReferenceException: Object reference not set to an instance of an object
at System.Collections.Concurrent.ConcurrentQueue`1[ConsoleApplication1.Program+TestStruct].TryDequeue (ConsoleApplication1.TestStruct& result) [0x00000] in <filename unknown>:0
at ConsoleApplication1.Program+<TestMonoConcurrentQueueBiggerThanReference>c__AnonStorey3.<>m__2 (System.Object x) [0x00000] in <filename unknown>:0
at System.Threading.Thread.StartInternal () [0x00000] in <filename unknown>:0
Unhandled Exception:
System.NullReferenceException: Object reference not set to an instance of an object
at System.Collections.Concurrent.ConcurrentQueue`1[ConsoleApplication1.Program+TestStruct].TryDequeue (ConsoleApplication1.TestStruct& result) [0x00000] in <filename unknown>:0
at ConsoleApplication1.Program+<TestMonoConcurrentQueueBiggerThanReference>c__AnonStorey3.<>m__2 (System.Object x) [0x00000] in <filename unknown>:0
at System.Threading.Thread.StartInternal () [0x00000] in <filename unknown>:0
Unhandled Exception:
System.NullReferenceException: Object reference not set to an instance of an object
at System.Collections.Concurrent.ConcurrentQueue`1[ConsoleApplication1.Program+TestStruct].TryDequeue (ConsoleApplication1.TestStruct& result) [0x00000] in <filename unknown>:0
at ConsoleApplication1.Program+<TestMonoConcurrentQueueBiggerThanReference>c__AnonStorey3.<>m__2 (System.Object x) [0x00000] in <filename unknown>:0
at System.Threading.Thread.StartInternal () [0x00000] in <filename unknown>:0
[ERROR] FATAL UNHANDLED EXCEPTION: System.Exception: bad y
at ConsoleApplication1.Program+<TestMonoConcurrentQueueBiggerThanReference>c__AnonStorey3.<>m__2 (System.Object x) [0x00000] in <filename unknown>:0
at System.Threading.Thread.StartInternal () [0x00000] in <filename unknown>:0
[ERROR] FATAL UNHANDLED EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object
at System.Collections.Concurrent.ConcurrentQueue`1[ConsoleApplication1.Program+TestStruct].TryDequeue (ConsoleApplication1.TestStruct& result) [0x00000] in <filename unknown>:0
at ConsoleApplication1.Program+<TestMonoConcurrentQueueBiggerThanReference>c__AnonStorey3.<>m__2 (System.Object x) [0x00000] in <filename unknown>:0
at System.Threading.Thread.StartInternal () [0x00000] in <filename unknown>:0
[ERROR] FATAL UNHANDLED EXCEPTION: System.NullReferenceException: Object reference not set to an instance of an object
at System.Collections.Concurrent.ConcurrentQueue`1[ConsoleApplication1.Program+TestStruct].TryDequeue (ConsoleApplication1.TestStruct& result) [0x00000] in <filename unknown>:0
at ConsoleApplication1.Program+<TestMonoConcurrentQueueBiggerThanReference>c__AnonStorey3.<>m__2 (System.Object x) [0x00000] in <filename unknown>:0
at System.Threading.Thread.StartInternal () [0x00000] in <filename unknown>:0
private static void TestMonoConcurrentQueueBiggerThanReference()
{
var queue = new ConcurrentQueue<TestStruct>();
var waits = new List<AutoResetEvent>();
for(int i=0;i<5;i++)
{
int q = i;
waits.Add(new AutoResetEvent(false));
var t = new Thread(x =>
{
for(int j=0;j<100000000;j++)
{
if(j% 1000000 == 0) Console.Write(".");
queue.Enqueue(new TestStruct(0x11223344, 0x99887766));
TestStruct item;
if(queue.TryDequeue(out item))
{
if(item.X != 0x11223344) throw new Exception("bad x");
if(item.Y != 0x99887766) throw new Exception("bad y");
} else
{
//throw new Exception("unable to read."); <~~~~ should never hit this.
}
}
waits[q].Set();
});
t.Start();
}
Console.WriteLine("waiting.");
waits.ForEach(x => x.WaitOne());
Console.WriteLine("done.");
}
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