linux-kernel - Re: [tip:x86/asm] x86/entry, locking/lockdep: Move lockdep_sys_exit() to prepare_exit_to

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Message-ID: <CALCETrVgksgbXc5pMpnQqQjQZsrVBCmoGqXC8+9q7QX4MX62JQ@mail.gmail.com>
Date:	Fri, 9 Oct 2015 12:34:49 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Andrew Lutomirski <luto@...nel.org>,
	"H. Peter Anvin" <hpa@...or.com>, Borislav Petkov <bp@...en8.de>,
	Ingo Molnar <mingo@...nel.org>,
	Brian Gerst <brgerst@...il.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	"linux-tip-commits@...r.kernel.org" 
	<linux-tip-commits@...r.kernel.org>
Subject: Re: [tip:x86/asm] x86/entry, locking/lockdep: Move lockdep_sys_exit()
 to prepare_exit_to_usermode()

On Thu, Oct 8, 2015 at 1:59 AM, Peter Zijlstra <peterz@...radead.org> wrote:
> On Wed, Oct 07, 2015 at 09:17:44AM -0700, tip-bot for Andy Lutomirski wrote:
>> Commit-ID:  72f924783b8a87e4454516520ffb5f35e4930371
>> Gitweb:     http://git.kernel.org/tip/72f924783b8a87e4454516520ffb5f35e4930371
>> Author:     Andy Lutomirski <luto@...nel.org>
>> AuthorDate: Mon, 5 Oct 2015 17:47:54 -0700
>> Committer:  Ingo Molnar <mingo@...nel.org>
>> CommitDate: Wed, 7 Oct 2015 11:34:07 +0200
>>
>> x86/entry, locking/lockdep: Move lockdep_sys_exit() to prepare_exit_to_usermode()
>>
>> Rather than worrying about exactly where LOCKDEP_SYS_EXIT should
>> go in the asm code, add it to prepare_exit_from_usermode() and
>> remove all of the asm calls that are followed by
>> prepare_exit_to_usermode().
>>
>> LOCKDEP_SYS_EXIT now appears only in the syscall fast paths.
>
> Does that not pose a risk that something that always takes the slow path
> (signals? tracing?) will leak a lock to userspace?

No, because while LOCKDEP_SYS_EXIT only happens in the fast path,
lockdep_sys_exit (lowercase) will get called in the other cases.

--Andy
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