linux-kernel - Re: [RFC, PATCH 3/3] use CLONE_KERNEL

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Date:	Mon, 9 Apr 2007 11:19:21 -0500
From:	"Serge E. Hallyn" <serge@...lyn.com>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Davide Libenzi <davidel@...ilserver.org>,
	Ingo Molnar <mingo@...e.hu>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Robin Holt <holt@....com>, Roland McGrath <roland@...hat.com>,
	linux-kernel@...r.kernel.org, linux-arch@...r.kernel.org
Subject: Re: [RFC, PATCH 3/3] use CLONE_KERNEL_THREAD

Quoting Oleg Nesterov (oleg@...sign.ru):
> For review only.
> 
> Add CLONE_KERNEL_THREAD to kthread_create() and change reparent_to_init()
> to match CLONE_KERNEL_THREAD.
> 
> Signed-off-by: Oleg Nesterov <oleg@...sign.ru>
> 
>  kthread.c |    2 +-
>  exit.c    |   20 +++++++++-----------
>  2 files changed, 10 insertions(+), 12 deletions(-)
> 
> --- 2.6.21-rc5-mm4/kernel/kthread.c~3_USE	2007-04-05 12:18:28.000000000 +0400
> +++ 2.6.21-rc5-mm4/kernel/kthread.c	2007-04-08 19:18:59.000000000 +0400
> @@ -120,7 +120,7 @@ static void keventd_create_kthread(struc
>  	int pid;
>  
>  	/* We want our own signal handler (we take no signals by default). */
> -	pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | SIGCHLD);
> +	pid = kernel_thread(kthread, create, CLONE_FS | CLONE_FILES | CLONE_KERNEL_THREAD);
>  	if (pid < 0) {
>  		create->result = ERR_PTR(pid);
>  	} else {
> --- 2.6.21-rc5-mm4/kernel/exit.c~3_USE	2007-04-08 19:06:27.000000000 +0400
> +++ 2.6.21-rc5-mm4/kernel/exit.c	2007-04-08 19:23:18.000000000 +0400
> @@ -279,28 +279,26 @@ static int has_stopped_jobs(struct pid *
>  }
>  
>  /**
> - * reparent_to_init - Reparent the calling kernel thread to the init task of the pid space that the thread belongs to.
> + * reparent_kthread - Reparent the calling kernel thread to swapper.
>   *
>   * If a kernel thread is launched as a result of a system call, or if
> - * it ever exits, it should generally reparent itself to init so that
> - * it is correctly cleaned up on exit.
> + * it ever exits, it should generally reparent itself so that it is
> + * correctly cleaned up on exit.
>   *
>   * The various task state such as scheduling policy and priority may have
>   * been inherited from a user process, so we reset them to sane values here.
>   *
> - * NOTE that reparent_to_init() gives the caller full capabilities.
> + * NOTE that reparent_kthread() gives the caller full capabilities.
>   */
> -static void reparent_to_init(void)
> +static void reparent_kthread(void)

Thanks.  The use of 'child_reaper(current)' makes it clear that
'reparent_to_init' had turned into a confusing name in the name
of per-pidspace inits.

-serge

>  {
>  	write_lock_irq(&tasklist_lock);
>  
> -	/* Reparent to init */
>  	remove_parent(current);
> -	current->parent = child_reaper(current);
> -	add_parent(current);
>  
> -	/* Set the exit signal to SIGCHLD so we signal init on exit */
> -	current->exit_signal = SIGCHLD;
> +	current->parent = &init_task;
> +	add_parent(current);
> +	current->exit_signal = -1;
>  
>  	if (!has_rt_policy(current) && (task_nice(current) < 0))
>  		set_user_nice(current, 0);
> @@ -423,7 +421,7 @@ void daemonize(const char *name, ...)
>  	current->files = init_task.files;
>  	atomic_inc(&current->files->count);
>  
> -	reparent_to_init();
> +	reparent_kthread();
>  }
>  
>  EXPORT_SYMBOL(daemonize);
> 
> -
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