Re: same pid ?
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2011/2/11 Steve Graegert (スティーブ) <graegerts@xxxxxxxxx>: > POSIX.1 requires threads to share a couple of attributes (mainly > process attributes) like the process ID, open FDs and many others. > What you are referring to ("everything as task") is the fact that each > thread is associated with a single scheduling entity within the kernel > implementing a 1:1 mapping. Yet, threads created within the same > process share a single PID. > Thanks steve. I found some more info. posix thread uses CLONE_THREAD with clone() system call. i quoted from - man clone CLONE_THREAD (since Linux 2.4.0-test8) If CLONE_THREAD is set, the child is placed in the same thread group as the calling process. To make the remainder of the discussion of CLONE_THREAD more readable, the term "thread" is used to refer to the processes within a thread group. Thread groups were a feature added in Linux 2.4 to support the POSIX threads notion of a set of threads that share a single PID. Internally, this shared PID is the so-called thread group identifier (TGID) for the thread group. Since Linux 2.4, calls to getpid(2) return the TGID of the caller. -Ratheesh > On Fri, Feb 11, 2011 at 03:18, ratheesh k <ratheesh.ksz@xxxxxxxxx> wrote: >>>On Fri, Feb 11, 2011 at 4:56 AM, Jonathan Isom <jeisom@xxxxxxxxx> wrote: >>> Newer distros use Native POSIX Thread Library (NPTL). They return the same pid. >> >> if linux treats every thing as task (both thread and process ) and >> CLONE_PID flag is obsolete, i expected unique pid. > > You are advised to consult pthreads(7) to make yourself familiar with the topic. > > Steve > -- To unsubscribe from this list: send the line "unsubscribe linux-c-programming" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html