Re: [PATCH] memcg: Free spare array to avoid memory leak

[KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>]

On Fri, 09 Mar 2012 12:07:32 +0800
Sha Zhengju <handai.szj@gmail.com> wrote:

> On 03/09/2012 11:40 AM, KAMEZAWA Hiroyuki wrote:
> > On Tue,  6 Mar 2012 20:13:24 +0800
> > Sha Zhengju<handai.szj@gmail.com>  wrote:
> >
> >> From: Sha Zhengju<handai.szj@taobao.com>
> >>
> >> When the last event is unregistered, there is no need to keep the spare
> >> array anymore. So free it to avoid memory leak.
> >>
> >> Signed-off-by: Sha Zhengju<handai.szj@taobao.com>
> >>
> >> ---
> >>   mm/memcontrol.c |    6 ++++++
> >>   1 files changed, 6 insertions(+), 0 deletions(-)
> >>
> >> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> >> index 22d94f5..3c09a84 100644
> >> --- a/mm/memcontrol.c
> >> +++ b/mm/memcontrol.c
> >> @@ -4412,6 +4412,12 @@ static void mem_cgroup_usage_unregister_event(struct cgroup *cgrp,
> >>   swap_buffers:
> >>   	/* Swap primary and spare array */
> >>   	thresholds->spare = thresholds->primary;
> >> +	/* If all events are unregistered, free the spare array */
> >> +	if (!new) {
> >> +		kfree(thresholds->spare);
> >> +		thresholds->spare = NULL;
> >> +	}
> >> +
> > Could you clear thresholds->primary ? I don't like a pointer points to freed memory.
> Do you meaning I should set ‘thresholds->primary = NULL‘ ？
> But the following rcu_assign_pointer will do this :
> 
> +	/* If all events are unregistered, free the spare array */
> +	if (!new) {
> +		kfree(thresholds->spare);
> +		thresholds->spare = NULL;
> +	}
> +
>   	rcu_assign_pointer(thresholds->primary, new);<---------*HERE*
> 

Hm, ok.

Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>


BTW, can memory cgroup be destroyed while there are registered events ?



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