[PATCH 2.6.21-rc4] kernel/exit: Fix a comment and code contradiction

[PATCH 2.6.21-rc4] kernel/exit: Fix a comment and code contradiction

[Ahmed S. Darwish]

Hi list,

Comment in release_task() claims that group leader's parent process 
is signalled only if it desires so, which is not true.

Signed-off-by: Ahmed S. Darwish <darwish.07@gmail.com>
---

To save your time, here's the contradictory code which don't appear in 
the patch (appears after its last line):

      leader = p->group_leader;
      if (leader != p && thread_group_empty(leader) && leader->exit_state == EXIT_ZOMBIE) {
		BUG_ON(leader->exit_signal == -1);
		do_notify_parent(leader, leader->exit_signal);


diff --git a/kernel/exit.c b/kernel/exit.c
index f132349..4a0a35f 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -152,7 +152,7 @@ repeat:
 	/*
 	 * If we are the last non-leader member of the thread
 	 * group, and the leader is zombie, then notify the
-	 * group leader's parent process. (if it wants notification.)
+	 * group leader's parent process.
 	 */
 	zap_leader = 0;
 	leader = p->group_leader;

-- 
Ahmed S. Darwish
http://darwish.07.googlepages.com

Re: [PATCH 2.6.21-rc4] kernel/exit: Fix a comment and code contradiction

[Johannes Weiner]

Hi,

On Sat, Mar 17, 2007 at 08:21:32AM +0200, Ahmed S. Darwish wrote:
> Comment in release_task() claims that group leader's parent process 
> is signalled only if it desires so, which is not true.

AFAIS, `if it wants notification' means, it does not ignore its children
via SIG_IGN als handler for SIGCHLD.

do_notify_parent() checks if the parent wants to get informed about the
child states.

- Johannes

Re: [PATCH 2.6.21-rc4] kernel/exit: Fix a comment and code contradiction

[Ahmed S. Darwish]

[Johannes please use replay-to-all to notify all readers]

On 2007-03-17 9:45:36 Johannes Weiner wrote:
> On Sat, Mar 17, 2007 at 08:21:32AM +0200, Ahmed S. Darwish wrote:
> > Comment in release_task() claims that group leader's parent process 
> > is signalled only if it desires so, which is not true.
>
> AFAIS, `if it wants notification' means, it does not ignore its children
> via SIG_IGN als handler for SIGCHLD.
>

AFAIK, exit_signal = -1 means that the parent don't want to be signalled,
like what happenes when using CLONE_THREAD. 

But it's even signalled in that case (after issuing a BUG):
   BUG_ON(leader->exit_signal == -1);
   do_notify_parent(leader, leader->exit_signal);

> do_notify_parent() checks if the parent wants to get informed about the
> child states.
>

Yes it does the check but it notifies the given task_struct anyway:

	BUG_ON(sig == -1);
	[ Continue parent notification normally ]
-- 
Ahmed S. Darwish
http://darwish.07.googlepages.com