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Date: Mon, 08 Oct 2012 14:34:55 -0600
From: David Ahern <dsahern@gmail.com>
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To: Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
CC: linux-kernel@vger.kernel.org, mingo@kernel.org, peterz@infradead.org,
        fweisbec@gmail.com, Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com>,
        Dong Hao <haodong@linux.vnet.ibm.com>
Subject: Re: [PATCH 07/12] perf kvm: handle realloc failures
References: <1349716656-48165-1-git-send-email-dsahern@gmail.com> <1349716656-48165-8-git-send-email-dsahern@gmail.com> <20121008201956.GE2631@ghostprotocols.net>
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On 10/8/12 2:19 PM, Arnaldo Carvalho de Melo wrote:
> Em Mon, Oct 08, 2012 at 11:17:31AM -0600, David Ahern escreveu:
>> Save previous pointer and free on failure.
>
> <SNIP>
>
>> +	prev = event->vcpu;
>>   	event->vcpu = realloc(event->vcpu,
>>   			      event->max_vcpu * sizeof(*event->vcpu));
>>   	if (!event->vcpu) {
>> +		free(prev);
>>   		pr_err("Not enough memory\n");
>
> Unfamiliar way of doing it, usually we do it like:
>
>    	vcpu = realloc(event->vcpu, event->max_vcpu * sizeof(*event->vcpu));
>
> 	if (!vcpu) {
>    		pr_err("Not enough memory\n");
> 		return -1;
> 	}
>
> 	event->vcpu = vcpu;
>
> I.e. we don't trow away the old value of event->vcpu.

right. Command is going to exit on a failure, so leaving the old value 
does not have any impact. I can leave the old if you want it for 
consistency.

David