linux-kernel - Re: [patch] slub: provide /proc/slabinfo

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Message-ID: <alpine.LFD.1.00.0801041648470.2811@woody.linux-foundation.org>
Date:	Fri, 4 Jan 2008 16:49:06 -0800 (PST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Arjan van de Ven <arjan@...radead.org>
cc:	Ingo Molnar <mingo@...e.hu>, Theodore Tso <tytso@....edu>,
	Andi Kleen <andi@...stfloor.org>,
	Christoph Lameter <clameter@....com>, Willy Tarreau <w@....eu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Hellwig <hch@...radead.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: [patch] slub: provide /proc/slabinfo



On Fri, 4 Jan 2008, Arjan van de Ven wrote:
> 
> this is the part I'm not very thrilled about... at least on first sight 
> it looks like a user can now hold the read sem over system calls, and 
> for as long as it wants.

No, you misunderstand how seq-files work.

The start/stop sequence is done only overone single kernel buffer 
instance, not over the whole open/close (or even the copy to user space).

It's expressly designed so that you can hold locks (including spinlocks 
etc), and will not do any blocking ops (well - your *callbacks* can you 
blocking ops, but the seq_file stuff itself won't) between start/stop.

		Linus
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