linux-kernel - Re: [PATCH 07/12] perf kvm: handle realloc failures

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Message-ID: <507338EF.3060801@gmail.com>
Date:	Mon, 08 Oct 2012 14:34:55 -0600
From:	David Ahern <dsahern@...il.com>
To:	Arnaldo Carvalho de Melo <acme@...stprotocols.net>
CC:	linux-kernel@...r.kernel.org, mingo@...nel.org,
	peterz@...radead.org, fweisbec@...il.com,
	Xiao Guangrong <xiaoguangrong@...ux.vnet.ibm.com>,
	Dong Hao <haodong@...ux.vnet.ibm.com>
Subject: Re: [PATCH 07/12] perf kvm: handle realloc failures

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

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