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    SubjectRe: Thread_Id

    Jakub Jelinek wrote:

    >On Thu, Jul 14, 2005 at 02:25:43PM +0200, Arjan van de Ven wrote:
    >
    >
    >>pure luck. NPTL threading uses it to store a pointer to per thread info
    >>structure; other threading (linuxthreads) may have stored a pid there to
    >>identify the internal thread. nptl is 2.6 only so you might have
    >>switched implementation of threading when you switched kernels.
    >>
    >>
    >
    >Actually, in linuxthreads what pthread_self () returned has the first slot
    >in its internal threads array (up to max number of supported threads)
    >that was unused at thread creation time in the low order bits and sequence
    >number of thread creation in its high order bits.
    >So unless you are using yet another threading library (I thought NGPT
    >is dead for years...), the claim that you get the same numbers from
    >gettid() syscall under NPTL as pthread_self () gives you under LinuxThreads
    >is simply not true. And you certainly shouldn't be using gettid ()
    >syscall in NPTL, as it is just an implementation detail that there is
    >a 1:1 mapping between NPTL threads and kernel threads. It can change
    >at any time.
    >
    >
    >
    Which ever is the implementation its expected to be backward compatible.
    Especially thread libraries. As lot of applications using that.

    rvk

    > Jakub
    >
    >
    >

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