linux-kernel - Re: [announce] "kill the Big Kernel Lock (BKL)" tree

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Wed, 14 May 2008 14:56:37 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Jonathan Corbet <corbet@....net>
cc:	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Thomas Gleixner <tglx@...utronix.de>,
	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Alexander Viro <viro@....linux.org.uk>,
	linux-kernel@...r.kernel.org
Subject: Re: [announce] "kill the Big Kernel Lock (BKL)" tree 



On Wed, 14 May 2008, Jonathan Corbet wrote:
> 
> There's also every char device open() method - a rather long list in its
> own right.  I'd be surprised if one in ten of them really needs it, but
> one has to look...

I don't think there are *that* many. I found only 83 instances of 
"register_chrdev()" in the kernel, so the open methods should be pretty 
limited.

Of course, some open methods call other sub-registrations, but you'd start 
off by moving the lock_kernel() down just *one* stage. 

So it literally should be:
 - remove one lock_kernel/unlock_kernel pair in fs/char_dev.c
 - add max 83 pairs in the places that register those things
 - external modules will need to add it themselves some day.

> 1: We could add an unlocked_open() to the file_operations structure;
>    drivers could be converted over as they are verified not to need the
>    BKL on open.  Disadvantages are that it grows this structure for a
>    relatively rare case - most open() calls already don't need the BKL.
>    But it's a relatively easy path without flag days.

I really don't think it's worth the pain. See above. The numbers aren't 
that huge, and external modules simply aren't a pressing enough issue.

		Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/