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Message-ID: <957BD1C2BF3CD411B6C500A0C944CA260216C228@pdsmsx32.pd.intel.com>
From: "Hu, Boris" <boris.hu@intel.com>
To: "NPTL list (E-mail)" <phil-list@redhat.com>
Cc: "Linux Kernel ML (E-mail)" <linux-kernel@vger.kernel.org>
Subject: what's the relationship between tgid, tid and pid ?
Date: Fri, 6 Dec 2002 03:36:21 +0800 
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Linux 2.5.49
NTPL 0.10

I learned from the kernel source. sys_getpid() returns tgid and 
sys_gettid() returns pid. Moreover, 
/kernel/source/fork.c
copy_process() 
771 if (clone_flags & CLONE_PARENT_SETTID)
772 if (put_user(p->pid, parent_tidptr))  // parent_tidptr is tid in struct
pthread
                                   ....
It seems tid = pid, while tgid is head pthread pid. 

But the following lines let me confused.
/kernel/source/fork.c
copy_process()              
893         p->tgid = p->pid;
894         p->group_leader = p;
every pthread_create()->sys_clone()->do_fork()->copy_process()
p->tgid will be overwritten every time?

any comments? thanks. 

  Boris
=========================
To know what I don't know
To learn what I don't know
To contribute what I know
=========================

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