Re: clone() <-> getpid() bug in 2.6?

[Russell Leighton]

I have read the discussion on this issue and I wanted to get 
confirmation of my understanding...

Issue:
   It seems glibc is caching getpid() which is wrong and breaks 
programs like mine.

   You are using an older version of  glibc than I and that is why you 
could run the test program.

Given the above, that means that:
   Upgrading my kernel on the FedoraCore2 system won't help because the 
bug is in glibc

   Assuming that this is a "new" feature of glibc, any others upgrading 
would then starting seeing this bug

Linus Torvalds wrote:

> On Sat, 5 Jun 2004, Russell Leighton wrote:
>  
>
> > I have a test program (see attached) that shows what looks like a bug in 
> > 2.6.5-1.358 (FedoraCore2)...and breaks my program :(
> >
> > In summary, I am doing:
> >
> > clone(run_thread, stack + sizeof(stack) -1,
> >            CLONE_FS|CLONE_FILES|CLONE_VM|SIGCHLD, NULL))
> >
> > According to the man page the child process should have its own pid as 
> > returned by getpid()...much like fork().
> >
> > In 2.6 the child receives the parent's pid from getpid(), while 2.4 
> > works as documented:
> >
> > In 2.4 the test program does:
> > parent pid: 26647
> > clone returned pid: 26648
> > thread reported pid: 26648
> >
> > In 2.6 the test program does:
> > parent pid: 16665
> > thread reported pid: 16665
> > clone returned pid: 16666
> >    
>
> Hmm.. The above is the correct behaviour if you use CLONE_THREAD 
> ("getpid()" will then return the _thread_ ID), but it shouldn't happen 
> without that. And clearly you don't have it set.
>
> And indeed, it doesn't happen for me on my system:
>
> 	parent pid: 13552
> 	thread reported pid: 13553
> 	clone returned pid: 13553
>
> so I wonder if either the Fedora libc always adds that CLONE_THREAD thing
> to the clone() calls, or whether the FC2 kernel is buggy.
>
> Arjan?
>
> 		Linus
>
>
>  

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