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Date:   Mon, 14 Jan 2019 11:09:32 -0600
From:   Josh Poimboeuf <jpoimboe@redhat.com>
To:     Joe Lawrence <joe.lawrence@redhat.com>
Cc:     Nicolai Stange <nstange@suse.de>, linux-kernel@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, live-patching@vger.kernel.org,
        Torsten Duwe <duwe@lst.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Jiri Kosina <jkosina@suse.cz>,
        Balbir Singh <bsingharora@gmail.com>
Subject: Re: ppc64le reliable stack unwinder and scheduled tasks
Message-ID: <20190114170932.awhuv7livfxhrcee@treble>
References: <7f468285-b149-37e2-e782-c9e538b997a9@redhat.com>
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 <20190111010808.GA17858@redhat.com>
 <87fttzbpid.fsf@suse.de>
 <20190114040937.GA6739@redhat.com>
 <877ef7bt6j.fsf@suse.de>
 <20190114164659.GA18643@redhat.com>
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On Mon, Jan 14, 2019 at 11:46:59AM -0500, Joe Lawrence wrote:
> @@ -158,11 +158,21 @@ save_stack_trace_tsk_reliable(struct task_struct *tsk,
>  			return 1; /* invalid backlink, too far up. */
>  		}
>  
> +		/* We can only trust the bottom frame's backlink, the rest
> +		 * of the frame may be uninitialized, continue to the next. */
> +		if (firstframe--)
> +			goto next;

Won't this decrement firstframe on every iteration, so when firstframe
is 0, it will decrement it to -1, causing it to 'goto next' on all
future iterations?

-- 
Josh