linux-kernel - Re: [PATCH v2] powerpc/watchpoint: Disable watchpoint hit by larx/stcx instructions

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Message-Id: <46YtKb2HHTz9sPM@ozlabs.org>
Date:   Thu, 19 Sep 2019 20:25:55 +1000 (AEST)
From:   Michael Ellerman <patch-notifications@...erman.id.au>
To:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>, mikey@...ling.org
Cc:     Ravi Bangoria <ravi.bangoria@...ux.ibm.com>,
        linux-kernel@...r.kernel.org, paulus@...ba.org,
        "Naveen N . Rao" <naveen.n.rao@...ux.vnet.ibm.com>,
        linuxppc-dev@...ts.ozlabs.org
Subject: Re: [PATCH v2] powerpc/watchpoint: Disable watchpoint hit by larx/stcx instructions

On Tue, 2019-09-10 at 13:15:13 UTC, Ravi Bangoria wrote:
> If watchpoint exception is generated by larx/stcx instructions, the
> reservation created by larx gets lost while handling exception, and
> thus stcx instruction always fails. Generally these instructions are
> used in a while(1) loop, for example spinlocks. And because stcx
> never succeeds, it loops forever and ultimately hangs the system.
> 
> Note that ptrace anyway works in one-shot mode and thus for ptrace
> we don't change the behaviour. It's up to ptrace user to take care
> of this.
> 
> Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.ibm.com>
> Acked-by: Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/bc01bdf6c5df5023272a7399962cf64f8fedc93e

cheers