linux-kernel - Re: [PATCH v3 1/1] ppc/crash: Reset spinlocks during crash

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Message-ID: <e304952f5177f85faff4560ded5aa1dad7af5fe2.camel@linux.ibm.com>
Date:   Wed, 01 Apr 2020 20:53:31 -0300
From:   Leonardo Bras <leonardo@...ux.ibm.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Paul Mackerras <paulus@...ba.org>,
        Michael Ellerman <mpe@...erman.id.au>,
        Enrico Weigelt <info@...ux.net>,
        Alexios Zavras <alexios.zavras@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Christophe Leroy <christophe.leroy@....fr>,
        linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/1] ppc/crash: Reset spinlocks during crash

Hello Peter, 

On Wed, 2020-04-01 at 11:26 +0200, Peter Zijlstra wrote:
> You might want to add a note to your asm/spinlock.h that you rely on
> spin_unlock() unconditionally clearing a lock.
> 
> This isn't naturally true for all lock implementations. Consider ticket
> locks, doing a surplus unlock will wreck your lock state in that case.
> So anybody poking at the powerpc spinlock implementation had better know
> you rely on this.

Good idea. I will add this to my changes and generate a v4.

Thank you,

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