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From: Linus Torvalds <torvalds@osdl.org>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: Marcelo Tosatti <marcelo.tosatti@cyclades.com>,
	Lukasz Trabinski <lukasz@wsisiz.edu.pl>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: uselib()  & 2.6.X?
Date: Fri, 7 Jan 2005 16:15:28 -0800 (PST)	[thread overview]
Message-ID: <Pine.LNX.4.58.0501071609540.2386@ppc970.osdl.org> (raw)
In-Reply-To: <1105136446.7628.11.camel@localhost.localdomain>



On Fri, 7 Jan 2005, Alan Cox wrote:
>
> Please don't use that for mainline - do_brk_locked doesn't follow kernel
> convention

I agree, I also find the "do_brk_locked()" naming confusing. To me it 
implies that we already _are_ locked, not that we're going to lock.

On the other hand, I think Alan's patch is equally confusing: the calling 
rules for "do_brk()" and "do_mmap()" are the same, and they are "caller 
takes mmap_sem". 

So I think you _both_ broke kernel conventions.

So I'd personally much prefer to just first fix the bug minimally (by just
taking the lock in the two places that need it), and then _separately_ say
"we should warn if anybody ever calls 'do_brk()' without the lock". That's 
how we tend to verify locking in other cases, ie we have things like

	if (!spin_is_locked(&t->sighand->siglock))
		BUG();

to verify the calling conventions. Same would go for mmap_sem (although we
don't seem to have any "sem_is_writelocked()" test - although you can fake
it with

	if (down_read_trylock(&mm->mmap_sem))
		BUG();

instead.

Now _that_ is a non-silent failure mode. The machine doesn't just silently 
deadlock: it tells you exactly what's wrong.

		Linus

  reply	other threads:[~2005-01-08  0:22 UTC|newest]

Thread overview: 42+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-01-07 15:59 uselib() & 2.6.X? Lukasz Trabinski
2005-01-07 17:07 ` Marcelo Tosatti
2005-01-07 20:27   ` linux-os
2005-01-07 22:29     ` Athanasius
2005-01-07 22:49   ` Alan Cox
2005-01-08  0:15     ` Linus Torvalds [this message]
2005-01-07 22:12       ` Marcelo Tosatti
2005-01-08 18:46         ` Linus Torvalds
2005-01-08 18:28           ` Marcelo Tosatti
2005-01-09  1:38             ` Linus Torvalds
2005-01-09 11:06               ` Marcelo Tosatti
2005-01-10  8:34                 ` Frank Steiner
2005-01-10 16:51                   ` Marcelo Tosatti
2005-01-10 18:28                   ` Alan Cox
2005-01-11  7:49                     ` Frank Steiner
2005-01-08 21:07           ` Andreas Schwab
2005-01-08 22:30             ` Barry K. Nathan
2005-01-08 23:21             ` Andi Kleen
2005-01-08 23:30               ` Alan Cox
2005-01-09  0:57                 ` Andi Kleen
2005-01-09  0:49             ` Andries Brouwer
2005-01-09  2:21               ` Jesper Juhl
2005-01-09  2:17                 ` Andries Brouwer
2005-01-08 21:47           ` Alan Cox
2005-01-11 22:51           ` [PATCH] make uselib configurable (was Re: uselib() & 2.6.X?) Barry K. Nathan
2005-01-11 23:42             ` Jesper Juhl
2005-01-11 23:59             ` Andries Brouwer
2005-01-12  1:06               ` Jesper Juhl
2005-01-12  1:18                 ` David Lang
2005-01-11 22:36                   ` Marcelo Tosatti
2005-01-12  2:32                     ` Barry K. Nathan
2005-01-12  0:56                       ` Marcelo Tosatti
2005-01-12  6:10                         ` Barry K. Nathan
2005-01-12 16:47                           ` Adrian Bunk
2005-01-12 17:10                             ` Barry K. Nathan
2005-01-12 20:16                     ` Matt Mackall
2005-01-12  2:12               ` Barry K. Nathan
2005-01-12  2:23                 ` David Lang
2005-01-12  2:30                 ` Adrian Bunk
2005-01-12  5:11                 ` Stephen Pollei
2005-01-12 16:54                   ` Adrian Bunk
2005-01-12  7:58               ` Christoph Hellwig

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