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From: David Howells <dhowells@redhat.com>
In-Reply-To: <20180403133543.GA26653@andrea>
References: <20180403133543.GA26653@andrea> <1522600912-6208-2-git-send-email-andrea.parri@amarulasolutions.com> <1522600912-6208-1-git-send-email-andrea.parri@amarulasolutions.com> <29562.1522759749@warthog.procyon.org.uk>
To: Andrea Parri <andrea.parri@amarulasolutions.com>
Cc: dhowells@redhat.com, paulmck@linux.vnet.ibm.com,
        Ingo Molnar <mingo@redhat.com>, Peter Zijlstra <peterz@infradead.org>,
        linux-kernel@vger.kernel.org, Andrea Parri <parri.andrea@gmail.com>,
        Alan Stern <stern@rowland.harvard.edu>,
        Will Deacon <will.deacon@arm.com>, Boqun Feng <boqun.feng@gmail.com>,
        Nicholas Piggin <npiggin@gmail.com>,
        Jade Alglave <j.alglave@ucl.ac.uk>,
        Luc Maranget <luc.maranget@inria.fr>,
        Akira Yokosawa <akiyks@gmail.com>
Subject: Re: [PATCH v2 1/3] locking: Document the semantics of spin_is_locked()
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Date: Tue, 03 Apr 2018 14:52:33 +0100
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Andrea Parri <andrea.parri@amarulasolutions.com> wrote:

> > It's more complicated than that.  This function is dangerous and should be
> > used with extreme care.  In the case where CONFIG_SMP=n the value is locked
> > one way or the other and it might be the wrong way.
> 
> You mean "unlocked"? (aka, return 0)

No, I mean "fixed", sorry.  We've had problems stemming from this before on UP
systems.

David