[Mono-list] CurrentTimeZone race condition - fix

[Jaroslaw Kowalski]

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Hi all!

Included is a patch that eliminates a race condition that occurs in
CurrentTimeZone.GetDaylightChanges() (in TimeZone.cs).

Before the patch, when 2 threads call DateTime.Now at the same time (for
the very first time in the whole program) an exception is thrown, when a
duplicate key is being added to the hashtable.

in <0x002ff> 00 System.Collections.Hashtable:PutImpl (object,object,bool)
in <0x00018> 00 System.Collections.Hashtable:Add (object,object)
in <0x00279> 00 System.CurrentTimeZone:GetDaylightChanges (int)
in <0x00028> 00 System.TimeZone:IsDaylightSavingTime (System.DateTime)
in <0x0002b> 00 System.CurrentTimeZone:GetUtcOffset (System.DateTime)
in <0x0008f> 00 System.DateTime:.ctor (bool,long)
in <0x00036> 00 System.DateTime:get_Now ()

The patch that adds a critical section in  GetDaylightChanges() which
fixes the problem. Can you, please add it to CVS?

Jarek

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