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Re: Calls to getpid() in clone'd child return parent's pid.

From: "Carlos O'Donell" <carlos at systemhalted dot org>
To: "Daniel Jacobowitz" <drow at false dot org>, libc-ports at sourceware dot org
Date: Fri, 15 Sep 2006 23:02:55 -0400
Subject: Re: Calls to getpid() in clone'd child return parent's pid.
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References: <119aab440609131910g2237f51frdd94774f03e1466@mail.gmail.com> <20060914030059.GA31135@nevyn.them.org> <119aab440609132102r2dae6015m67fa8051b4ae7952@mail.gmail.com> <20060914040359.GA32539@nevyn.them.org>

On 9/14/06, Daniel Jacobowitz <drow@false.org> wrote:

I've got no idea any more :-)  But not quite - I distinctly remember
some CLONE_VM handling.

It seems to be:

If CLONE_THREAD was set, skip touching the thread's PID/TID
If CLONE_VM was set, write -1 into the PID/TID
If neither CLONE_THREAD or CLONE_VM was set, then call
__NR_getpid and write that result into PID/TID.

If someone more knowledgable could respond that would rock.
My RESET_PID patch fixes tst-getpid1/2 and tst-align2, but
causes tst-cond16 and tst-cond17 to fail with:

pthread_mutex_lock.c:82: __pthread_mutex_lock: Assertion
`mutex->__data.__owner == 0' failed.

I it is sensitive to PID/TID because __owner is set to TID. The call
to do_clone, and subsequently ARCH_CLONE, has CLONE_VM set, but not
CLONE_THREAD. Therefore I am worried that writing "-1" into PID/TID is
incorrect.

Cheers,
Carlos.

References:
- Calls to getpid() in clone'd child return parent's pid.
  - From: Carlos O'Donell
- Re: Calls to getpid() in clone'd child return parent's pid.
  - From: Daniel Jacobowitz
- Re: Calls to getpid() in clone'd child return parent's pid.
  - From: Carlos O'Donell
- Re: Calls to getpid() in clone'd child return parent's pid.
  - From: Daniel Jacobowitz

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