linux-kernel - Re: [GIT, RFC] Killing the Big Kernel Lock

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Date:	Sun, 28 Mar 2010 23:58:54 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Jiri Kosina <jkosina@...e.cz>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Frederic Weisbecker <fweisbec@...il.com>,
	linux-kernel@...r.kernel.org, Matthew Wilcox <matthew@....cx>,
	Thomas Gleixner <tglx@...utronix.de>, jblunck@...e.de,
	Alan Cox <alan@...ux.intel.com>, Ingo Molnar <mingo@...e.hu>,
	gregkh@...e.de
Subject: Re: [GIT, RFC] Killing the Big Kernel Lock

Jiri Kosina <jkosina@...e.cz> writes:

> On Wed, 24 Mar 2010, Arnd Bergmann wrote:
>
>> I've spent some time continuing the work of the people on Cc and many others
>> to remove the big kernel lock from Linux and I now have bkl-removal branch
>> in my git tree at git://git.kernel.org/pub/scm/linux/kernel/git/arnd/playground.git
>> that lets me run a kernel on my quad-core machine with the only users of the BKL
>> being mostly obscure device driver modules.
>
> 	config USB
> 	        tristate "Support for Host-side USB"
> 	        depends on USB_ARCH_HAS_HCD && BKL
>
> Well, that's very interesting definition of "obscure" :)

>From a quick grep at least EHCI doesn't seem to need it?

Except for those two guys in core/*.c:

                        /* keep API that guarantees BKL */
                        lock_kernel();
                        retval = driver->ioctl(intf, ctl->ioctl_code, buf);
                        unlock_kernel();
                        if (retval == -ENOIOCTLCMD)
                                retval = -ENOTTY;

I guess that could be just moved into the low level modules with unlocked_ioctl

And one use in the usbfs which seems quite bogus and can be probably removed.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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