linux-kernel - Re: [PATCH 0/1] lockdep: Kill held_lock->check and "int check" arg of __lock

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Message-ID: <20140113183555.GA14125@redhat.com>
Date:	Mon, 13 Jan 2014 19:35:55 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
	Thomas Gleixner <tglx@...utronix.de>,
	Steven Rostedt <rostedt@...dmis.org>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH 0/1] lockdep: Kill held_lock->check and "int check" arg
	of __lock_acquire()

On 01/12, Peter Zijlstra wrote:
>
> On Sun, Jan 12, 2014 at 06:45:32PM +0100, Oleg Nesterov wrote:
> > But could someone please explain me what should lockdep_no_validate
> > actually do? 1704f47b5 "lockdep: Add novalidate class for dev->mutex
> > conversion" doesn't tell which kind of warnings it tries to avoid,
> > and it looks buggy (see another email from me).
>
> It should disable lock-order checks for the locks that set that as
> class. So we can still do the simple checks like detect if we free
> memory with a held lock in and make sure we do not return to userspace
> with a held lock; but the class should not participate in the lock
> graph.

Yes, this is what I more or less understood, but I was confused anyway.
Somehow I thought that this patch tries to suppress the warnings caused
by rw_semaphore -> mutex conversion, and I was completely puzzled. But
3142788b79 "drivers/base: Convert dev->sem to mutex" actually did the
semaphore -> mutex change!

Everything is clear now, thanks!

Oleg.

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