netdev - Re: [PATCH net 3/3] ipv6: Fix dst_entry refcnt bugs in ip6

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Message-ID: <1441234137.8932.209.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Wed, 02 Sep 2015 15:48:57 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Martin KaFai Lau <kafai@...com>
Cc:	netdev <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>,
	Kernel Team <kernel-team@...com>
Subject: Re: [PATCH net 3/3] ipv6: Fix dst_entry refcnt bugs in ip6_tunnel

On Wed, 2015-09-02 at 14:52 -0700, Martin KaFai Lau wrote:
> On Wed, Sep 02, 2015 at 02:30:45PM -0700, Eric Dumazet wrote:
> > Object cannot be freed until all cpus have exited their RCU sections.
> You meant the dst_destroy() here will wait for all cpus exited their RCU sections?
> 
> static inline void dst_free(struct dst_entry *dst)
> {
> 	if (dst->obsolete > 0)
> 		return;
> 	if (!atomic_read(&dst->__refcnt)) {
> 		dst = dst_destroy(dst);
> 		if (!dst)
> 			return;
> 	}
> 	__dst_free(dst);
> }

dst_free() is called after RCU grace period, in the case you are
interested in.

Look at dst_rcu_free() and rt_free()





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