netdev - Re: [PATCH 1/4] flow: virtualize flow cache entry methods

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Date:	Sun, 4 Apr 2010 14:19:41 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Timo Teräs <timo.teras@....fi>
Cc:	netdev@...r.kernel.org
Subject: Re: [PATCH 1/4] flow: virtualize flow cache entry methods

On Sun, Apr 04, 2010 at 09:07:12AM +0300, Timo Teräs wrote:
>
> With 1/4 only, the bundle deletion is not touched. In that case
> the policy GC deletes explicitly the bundles. The bundles get
> deleted immediately, and only the struct xfrm_policy might get
> held up allocated longer.
>
> The code flow would be:
> 1. xfrm_policy_kill() queues to GC
> 2. xfrm_policy_gc_kill() called from xfrm_policy_gc_task()
>    frees all bundles in that policy
> 3. xfrm_policy_gc_kill() releases it's reference
> 4. ... time passes (flush, randomization, or flow hit occurs)
> 5. flow cache releases it's final reference, calls
>    xfrm_policy_destroy() which only frees the xfrm_policy memory

With 1/4 only, you've removed the flow cache flush when policies
are deleted.  However, you don't add the flow cache flush to the
NETDEV_DOWN case until 2/4.  So with only 1/4, bundles (and hence
netdev objects) may be held for up to 10 minutes.

Cheers,
-- 
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Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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