diskLib Multi threading

[arent_t]

I am trying to use the vddk 1.1 in a multithreaded application, all goes fine for one thread but as soon as I kick of mutliple threads I get an AccessViolationException error on the diskLib_Open function.

I did exactly as written on page 24 of the programming guide, one main thread that initializes the library, then I start one or more threads that will "disklib_connect" and opens a seperate thread to get my diskhandle (disklib_open) , once I get the diskhandle I can access the disk. Now this works for the first worker thread but as soon as the a second thread tries to open disk (disklib_open) I get an access violation error ?

Anyone any suggestions on what I am doing wrong ?

Thanks,

Tom

[fixitchris]

Tom, can you post some code?

[admin · Accepted solution]

The guidelines for using vixDiskLib in a multi-threaded app are as follows (some of these are unnecessary, we are planning on fixing them)

This is from page 24, please disregard the section at the top.

• VixDiskLib_InitEx() or VixDiskLib_Init() should be called only once per process. VMware

recommends that you call them from the main thread.

• In the VixDiskLib_InitEx() or VixDiskLib_Init() call, you can leave the logging callbacks as NULL.

This causes VixDiskLib to provide default logging functions, which are not thread safe. If you are using

VDDK in a multithreaded environment, you should provide your own thread safe logging functions.

• When you call VixDiskLib_Open() and VixDiskLib_Close(), VDDK initializes and uninitializes a

number of libraries. Some of these libraries fail to work if called from multiple threads. For example, the

following call sequence does not work:

Thread 1: VixDiskLib_Open ...... VixDiskLib_Close

Thread 2: ................................... VixDiskLib_Open ...... VixDiskLib_Close

The workaround is to use one designated thread to do all opens and closes, and to have other worker threads

doing reads and writes.

I think your program may not be following the third guideline.

Thanks

Sudarsan

[arent_t]

Public Delegate Function getDiskHandle(byval connection as intptr, Byval filename as string) as intptr

Class Main

Shared m_getdiskHandle As getdiskHandle

Public Shared Sub main()

m_getdiskHandle = New getdiskHandle(AddressOf getMyDiskHandle)

DiskLib_Init(1, 1, Nothing, Nothing, Nothing, Nothing)

Dim nT As Thread = New Thread(AddressOf doDiskTask)

nT.IsBackground = True

nT.Name = "Thread 1"

nT.Start()

' So far so good !

Dim nT1 As Thread = New Thread(AddressOf doDiskTask)

nT1.IsBackground = True

nT1.Name = "Thread 2"

nT1.Start()

' Second thread tries to open the disk handle and I get an accessviolation error !?

End Sub

Public Shared Function getMyDiskHandle(ByVal connection As IntPtr, ByVal fileName As String) As Intptr vixDisk.Open(connection, fileName, Nothing, diskPtr)

return diskPtr

End Function

Public Shared Function doDiskTask()

Dim cnxParamsUID As VixDiskLibConnectParams = New VixDiskLibConnectParams

cnxParamsUID.serverName = Me.serverName

cnxParamsUID.credType = VixDiskLibCredType.VIXDISKLIB_CRED_UID

cnxParamsUID.creds.uid.userName = m_userName

cnxParamsUID.creds.uid.password = m_password

cnxParamsUID.vmxSpec = "moref=" + vmMor.Value

cnxParamsUID.port = Nothing

vixDiskLib.ConnectEx(cnxParamsUID, True, Nothing, Nothing, connPtr)

diskPtr = main.getMyDiskHandle(connPtr, diskBacking.fileName)

End Function

End Class

[arent_t]

Yes you were right, I didnt follow the 3rd guideline. its working now.

Thanks