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Date:   Thu, 24 May 2018 13:49:31 +0100
From:   Will Deacon <will.deacon@arm.com>
To:     Linus Torvalds <torvalds@linux-foundation.org>
Cc:     psodagud@codeaurora.org, Kees Cook <keescook@chromium.org>,
        Andy Lutomirski <luto@amacapital.net>,
        Will Drewry <wad@chromium.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Rik van Riel <riel@redhat.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Eric Biggers <ebiggers@google.com>,
        Frederic Weisbecker <fweisbec@gmail.com>, sherryy@android.com,
        Vegard Nossum <vegard.nossum@oracle.com>,
        Christoph Lameter <cl@linux.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Sasha Levin <alexander.levin@verizon.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Boqun Feng <boqun.feng@gmail.com>
Subject: Re: write_lock_irq(&tasklist_lock)
Message-ID: <20180524124928.GH8689@arm.com>
References: <0879f797135033e05e8e9166a3c85628@codeaurora.org>
 <20180523130547.GF26965@arm.com>
 <CA+55aFwKLBKdf3gdWkJSdewQYYXYYfN29SPT+etPqpopxA0CMQ@mail.gmail.com>
 <20180523153607.GD2983@arm.com>
 <CA+55aFy9mVCJUniAMVvJjqaa=ke2mx6HfkPhCGP54ncdh70peQ@mail.gmail.com>
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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@arm.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