Bug 24213 - ConcurrentBag.TryTake returns the same instance twice...
Summary: ConcurrentBag.TryTake returns the same instance twice...
Status: RESOLVED FIXED
Alias: None
Product: Class Libraries
Classification: Mono
Component: System ()
Version: master
Hardware: Macintosh Mac OS
: --- normal
Target Milestone: Untriaged
Assignee: marcos.henrich
URL:
Depends on:
Blocks:
 
Reported: 2014-11-02 10:14 UTC by mikey10
Modified: 2014-11-20 09:58 UTC (History)
2 users (show)

Tags:
Is this bug a regression?: ---
Last known good build:

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Status:
RESOLVED FIXED

Description mikey10 2014-11-02 10:14:12 UTC
One of my unit tests of an object pool implementation based on ConcurrentBag failed mysterious even on a non-concurrent tests...
Tracked down to something curiously at the ConcurrentBag. 

If u put 2049 unique object instances in a ConcurrentBag (<=2048 works fine...) and take out all of them, the first and the last taken object are equal ... scary...

Code to reproduce below...

var list = new List<Object>();
var bag = new ConcurrentBag<Object>();
for( int i = 0; i < 2049; i++ )
bag.Add( new Object() );

Assert.AreEqual( 2049, bag.Count );

for( int i = 0; i < 2049; i++ )
{
Object b = null;
Assert.IsTrue( bag.TryTake( out b ) );
list.Add( b );
}

Assert.IsFalse( Object.ReferenceEquals( list[0], list[2047] ), "first assert" );
Assert.IsFalse( Object.ReferenceEquals( list[0], list[2048] ), "second assert" );
Comment 1 marcos.henrich 2014-11-20 09:32:06 UTC
Hi Mikey,

Thank you for the detailed bug report.

The pull request for this issue can be found in the link below.
https://github.com/mono/mono/pull/1418
Comment 2 marcos.henrich 2014-11-20 09:58:04 UTC
Fixed in master de75999a8ad897f0b229b0a570a5a10302c03f3e.
https://github.com/mono/mono/commit/de75999a8ad897f0b229b0a570a5a10302c03f3e