linux-kernel - Re: write_lock_irq(&tasklist

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Date:   Thu, 24 May 2018 13:49:31 +0100
From:   Will Deacon <will.deacon@....com>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     psodagud@...eaurora.org, Kees Cook <keescook@...omium.org>,
        Andy Lutomirski <luto@...capital.net>,
        Will Drewry <wad@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Rik van Riel <riel@...hat.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Eric Biggers <ebiggers@...gle.com>,
        Frederic Weisbecker <fweisbec@...il.com>, sherryy@...roid.com,
        Vegard Nossum <vegard.nossum@...cle.com>,
        Christoph Lameter <cl@...ux.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Sasha Levin <alexander.levin@...izon.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Boqun Feng <boqun.feng@...il.com>
Subject: Re: write_lock_irq(&tasklist_lock)

On Wed, May 23, 2018 at 09:26:35AM -0700, Linus Torvalds wrote:
> On Wed, May 23, 2018 at 8:35 AM Will Deacon <will.deacon@....com> wrote:
> 
> > In other words, qrwlock requires consistent locking order wrt spinlocks.
> 
> I *thought* lockdep already tracked and detected this. Or is that only with
> with the sleeping versions?

There are patches in-flight to detect this:

https://marc.info/?l=linux-kernel&m=152483640529740&w=2k

as part of Boqun's work into recursive read locking.

Will