linux-kernel - Re: ppc64le reliable stack unwinder and scheduled tasks

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Message-ID: <20190114170932.awhuv7livfxhrcee@treble>
Date:   Mon, 14 Jan 2019 11:09:32 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Joe Lawrence <joe.lawrence@...hat.com>
Cc:     Nicolai Stange <nstange@...e.de>, linux-kernel@...r.kernel.org,
        linuxppc-dev@...ts.ozlabs.org, live-patching@...r.kernel.org,
        Torsten Duwe <duwe@....de>,
        Michael Ellerman <mpe@...erman.id.au>,
        Jiri Kosina <jkosina@...e.cz>,
        Balbir Singh <bsingharora@...il.com>
Subject: Re: ppc64le reliable stack unwinder and scheduled tasks

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