Re: [PATCH 2.6.13.1] Patch for invisible threads

[Sripathi Kodi <sripathik@in.ibm.com>]

Andrew,

Andrew Morton wrote:
> Sripathi Kodi <sripathik@in.ibm.com> wrote:
>
> > Hi,
> >
> > When the main thread of a multi-threaded program calls 'pthread_exit' before
> > other threads have exited, it results in the other threads becoming
> > 'invisible' to commands like 'ps'.
>
>
> This stuff is subtle.   Let me cc some subtle people.
>
>
> > Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>
> >
> > --- linux-2.6.13.1/kernel/exit.c	2005-09-12 02:46:26.000000000 -0500
> > +++ /home/sripathi/17794/patch_2.6.13.1/exit.c	2005-09-12 02:46:15.000000000 
> > -0500
> > @@ -463,9 +463,11 @@ static inline void __exit_fs(struct task
> >  	struct fs_struct * fs = tsk->fs;
> >
> >  	if (fs) {
> > -		task_lock(tsk);
> > -		tsk->fs = NULL;
> > -		task_unlock(tsk);
> > +		if (!thread_group_leader(tsk) || !atomic_read(&tsk->signal->live)) {
> > +			task_lock(tsk);
> > +			tsk->fs = NULL;
> > +			task_unlock(tsk);
> > +		}
> >  		__put_fs_struct(fs);
> >  	}
> >  }
>
>
> A comment in there would be nice.

Below is the patch with a comment.

Thanks and regards,
Sripathi.

Signed-off-by: Sripathi Kodi <sripathik@in.ibm.com>

--- linux-2.6.13.1/kernel/exit.c	2005-09-13 15:39:48.738542872 -0500
+++ /home/sripathi/17794/patch_2.6.13.1/exit.c	2005-09-13 15:39:27.367791720 
-0500
@@ -463,9 +463,13 @@ static inline void __exit_fs(struct task
 	struct fs_struct * fs = tsk->fs;

 	if (fs) {
-		task_lock(tsk);
-		tsk->fs = NULL;
-		task_unlock(tsk);
+		/* If tsk is thread group leader and if group still has alive
+		 * threads, those threads may use tsk->fs */
+		if (!thread_group_leader(tsk) || !atomic_read(&tsk->signal->live)) {
+			task_lock(tsk);
+			tsk->fs = NULL;
+			task_unlock(tsk);
+		}
 		__put_fs_struct(fs);
 	}
 }
-
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