linux-kernel - Re: [PATCH v2.6.36-rc7] init: don't call flush_scheduled_work() from do

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Message-Id: <20101021171203.37d0d6d6.akpm@linux-foundation.org>
Date:	Thu, 21 Oct 2010 17:12:03 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Tejun Heo <tj@...nel.org>
Cc:	lkml <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: [PATCH v2.6.36-rc7] init: don't call flush_scheduled_work()
 from do_initcalls()

On Fri, 15 Oct 2010 17:13:24 +0200
Tejun Heo <tj@...nel.org> wrote:

> It's unclear what flush_scheduled_work() in do_initcalls() tries to
> achieve.  The call doesn't make much sense - there already are
> multiple system workqueues which aren't affected by
> flush_scheduled_wokr() and subsystems are free to create and use their
> own.  Ordering requirements are and should be expressed explicitly.
> 
> Drop the call to prepare for deprecation and removal of
> flush_scheduled_work().
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> ---
> If no one objects, I'll route this through wq tree.
> 
> Thank you.
> 
>  init/main.c |    3 ---
>  1 file changed, 3 deletions(-)
> 
> Index: work/init/main.c
> ===================================================================
> --- work.orig/init/main.c
> +++ work/init/main.c
> @@ -778,9 +778,6 @@ static void __init do_initcalls(void)
> 
>  	for (fn = __early_initcall_end; fn < __initcall_end; fn++)
>  		do_one_initcall(*fn);
> -
> -	/* Make sure there is no pending stuff from the initcall sequence */
> -	flush_scheduled_work();
>  }
> 

hm, that predates the initial 2002 BK tree.

If some initcall function leaves a work scheduled and doesn't flush it
then free_initmem() can come along and pull the rug out from under its
feet.  Then you will own both pieces :)

If you really don't like people sending you angry emails then I suppose
you could add some warning here if a scheduled work is pending, and
that the scheduled work's callback existed in init.text memory.  Which
would be a bit of a pain to implement.

Oh well.  The oops traces will make it fairly clear what happened.
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