Re: [PATCH, RFC] char dev BKL pushdown

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To: Jonathan Corbet <corbet@...>
Cc: Linus Torvalds <torvalds@...>, Ingo Molnar <mingo@...>, Andrew Morton <akpm@...>, Peter Zijlstra <a.p.zijlstra@...>, Thomas Gleixner <tglx@...>, Alan Cox <alan@...>, Alexander Viro <viro@...>, <linux-kernel@...>, Wim Van Sebroeck <wim@...>
Date: Tuesday, May 20, 2008 - 1:21 pm

On Tuesday 20 May 2008, Jonathan Corbet wrote:

Right, unless Alan or Wim are confident enough that removing the
BKL won't break the drivers (more than they are today).
Almost all of the open functions go along the lines of

int open(struct file *f, struct inode *i)
{
	if (wd_is_open)
		return -EBUSY;
	wd_is_open = 1;
	
	start_wd();

	return nonseekable_open(f, i);
}

nonseekable_open doesn't need the BKL by itself, and the wd_is_open
variable is protected by the misc_mtx mutex.
I can't see any scenario in which start_wd() would need the BKL, or
where a watchdog driver needs cycle_kernel_lock(), but I was't confident
enough about that assessment, because I'm not really familiar with
the drivers.


I've done a semi-automated split and applied the patches on top of your
tree. You can pull these from

git://git.kernel.org/pub/scm/linux/kernel/git/arnd/cell-2.6 bkl-removal

(I guess I should do a separate tree for it, will do that if more stuff
comes up.)

	Arnd <><
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Messages in current thread:
[announce] "kill the Big Kernel Lock (BKL)" tree, Ingo Molnar, (Wed May 14, 1:49 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Linus Torvalds, (Thu May 15, 1:41 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Arjan van de Ven, (Thu May 15, 4:27 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Peter Zijlstra, (Thu May 15, 4:45 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Arjan van de Ven, (Thu May 15, 5:22 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Linus Torvalds, (Wed May 14, 2:41 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Ingo Molnar, (Wed May 14, 3:41 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Frederik Deweerdt, (Wed May 14, 4:05 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Andi Kleen, (Wed May 14, 2:30 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Andi Kleen, (Wed May 14, 5:13 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, H. Peter Anvin, (Wed May 14, 5:16 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Linus Torvalds, (Wed May 14, 5:45 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Andi Kleen, (Wed May 14, 6:03 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Andi Kleen, (Thu May 15, 10:27 am)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Andi Kleen, (Fri May 16, 6:21 am)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Ingo Molnar, (Thu May 15, 4:02 am)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree , Jonathan Corbet, (Wed May 14, 5:45 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree , Jan Engelhardt, (Thu May 15, 4:44 am)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Diego Calleja, (Thu May 15, 10:54 am)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree , Linus Torvalds, (Wed May 14, 5:56 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree , Jonathan Corbet, (Wed May 14, 6:07 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree , Linus Torvalds, (Wed May 14, 6:14 pm)
[PATCH, RFC] char dev BKL pushdown , Jonathan Corbet, (Fri May 16, 11:44 am)
Re: [PATCH, RFC] char dev BKL pushdown , Linus Torvalds, (Sat May 17, 5:58 pm)
Re: [PATCH, RFC] char dev BKL pushdown , Jonathan Corbet, (Sun May 18, 4:07 pm)
Re: [PATCH, RFC] char dev BKL pushdown , Linus Torvalds, (Fri May 16, 12:30 pm)
Re: [PATCH, RFC] char dev BKL pushdown , Jonathan Corbet, (Fri May 16, 12:43 pm)
Re: [PATCH, RFC] char dev BKL pushdown, Arnd Bergmann, (Sat May 17, 5:15 pm)
Re: [PATCH, RFC] char dev BKL pushdown , Jonathan Corbet, (Sun May 18, 4:26 pm)
Re: [PATCH, RFC] char dev BKL pushdown, Arnd Bergmann, (Mon May 19, 7:07 pm)
Re: [PATCH, RFC] char dev BKL pushdown , Jonathan Corbet, (Tue May 20, 11:13 am)
Re: [PATCH, RFC] char dev BKL pushdown, Arnd Bergmann, (Tue May 20, 1:21 pm)
Re: [PATCH, RFC] char dev BKL pushdown, Alan Cox, (Tue May 20, 2:51 pm)
[PATCH 1/3, RFC] misc char dev BKL pushdown, Arnd Bergmann, (Mon May 19, 7:26 pm)
Re: [PATCH 1/3, RFC] misc char dev BKL pushdown, Mike Frysinger, (Tue May 20, 7:01 pm)
Re: [PATCH 1/3, RFC] misc char dev BKL pushdown , Jonathan Corbet, (Tue May 20, 7:25 pm)
Re: [PATCH 1/3, RFC] misc char dev BKL pushdown, Mike Frysinger, (Wed May 21, 12:22 pm)
Re: [PATCH 1/3, RFC] misc char dev BKL pushdown, Alan Cox, (Tue May 20, 4:46 am)
Re: [PATCH 1/3, RFC] misc char dev BKL pushdown, Mike Frysinger, (Mon May 19, 8:07 pm)
Re: [PATCH 1/3, RFC] misc char dev BKL pushdown , Jonathan Corbet, (Mon May 19, 8:21 pm)
Re: [PATCH 1/3, RFC] misc char dev BKL pushdown, Mike Frysinger, (Mon May 19, 8:46 pm)
[PATCH 3/3, RFC] remove BKL from misc_open(), Arnd Bergmann, (Mon May 19, 7:34 pm)
Re: [PATCH, RFC] char dev BKL pushdown, Alan Cox, (Fri May 16, 12:22 pm)
Re: [PATCH, RFC] char dev BKL pushdown, Christoph Hellwig, (Fri May 16, 11:49 am)
[PATCH] kill empty chardev open/release methods, Christoph Hellwig, (Fri May 16, 12:03 pm)
Re: [PATCH] kill empty chardev open/release methods , Jonathan Corbet, (Sun May 18, 3:46 pm)
Re: [PATCH] kill empty chardev open/release methods, Alan Cox, (Fri May 16, 12:24 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Andi Kleen, (Wed May 14, 6:11 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Linus Torvalds, (Wed May 14, 6:16 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Andi Kleen, (Wed May 14, 6:21 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, John Stoffel, (Thu May 15, 11:05 am)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Andi Kleen, (Thu May 15, 11:10 am)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, John Stoffel, (Thu May 15, 11:18 am)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Andi Kleen, (Thu May 15, 11:45 am)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Kevin Winchester, (Fri May 16, 8:14 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Kevin Winchester, (Fri May 16, 8:37 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Linus Torvalds, (Wed May 14, 6:11 pm)
Re: [announce] "kill the Big Kernel Lock (BKL)" tree, Andi Kleen, (Wed May 14, 6:15 pm)