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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.


> Jakub

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