Hi Stefano & Dario, Did you follow carefully the instructions given at: http://root.cern.ch/root/htmldoc/TMapFile.html#TMapFile:SetMapAddress for SetMapAddress and MaptoAddress ? Rene Brun On 24 Apr 2002, Stefano Magni wrote: > Dear Rene & C, > We are developing a DAQ system that makes heavy use of IPC calls to > create and manage shared memories and message queues. > In the same time we would like to use the facilities provided by root to > share histograms among cooperating processes via TMapFile. > We run into a problem: > if we just invoke TMapFile::Create with default values, our producer > process crashes at the firt call of the fill method of a histogram in > the shared map file. > We noticed that the base address, shown by TMapFile, overlaps with one > of our shared memories. > We therefore decided (arbitrarily?) to force TMapFile to a fixed base > address using TMapFile::SetMapAddress specifying the last location > allocated to our shared memory segment. In this configuration everything > seems working properly. > Since the basic mechanism to allocate shared memory by means of IPC > calls does not provide a method to specify it's phyical location at > specified addresses, we suspect that this solution, albeit fixing our > problem, is not of a sufficiently general nature. > With the call to SetMapAddress we apparently fixed the problem of the > overlap with just one of our shared memories. How can we be sure to > prevent a clash with one of the other shared memories and/or the message > queue? > Does anyone have a suggestion about the proper way to handle the mix of > TMapFile and ICP calls? > > Stefano Magni & Dario Menasce > > -- > ********************************************** > Dr. Stefano Magni > I.N.F.N Via Celoria 16, Milano > tel : 0250317738 > ********************************************** >
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