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Subject: Re: ppc64le reliable stack unwinder and scheduled tasks
To:     Josh Poimboeuf <jpoimboe@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>
References: <7f468285-b149-37e2-e782-c9e538b997a9@redhat.com>
 <87bm4ocbbt.fsf@suse.de> <20190111010808.GA17858@redhat.com>
 <87fttzbpid.fsf@suse.de> <20190114040937.GA6739@redhat.com>
 <877ef7bt6j.fsf@suse.de> <20190114164659.GA18643@redhat.com>
 <20190114170932.awhuv7livfxhrcee@treble>
From:   Joe Lawrence <joe.lawrence@redhat.com>
Message-ID: <4b95b2f3-c5e8-4d21-88fe-9de6cd346954@redhat.com>
Date:   Mon, 14 Jan 2019 12:54:52 -0500
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On 1/14/19 12:09 PM, Josh Poimboeuf wrote:
> 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?
> 

Argg, yes, that should be:

if (!firstframe) {
	firstframe = 0;
	goto next;
}

Apologies for the monday-morning crap-patch.

/runsoff to find some more caffeine

-- Joe