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

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Message-ID: <20150902231031.GC78846@kafai-mba.local>
Date:	Wed, 2 Sep 2015 16:10:31 -0700
From:	Martin KaFai Lau <kafai@...com>
To:	Eric Dumazet <eric.dumazet@...il.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, Sep 02, 2015 at 03:48:57PM -0700, Eric Dumazet wrote:
> 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()
Yes for IPv4 FIB

Not for IPv6 FIB. F.e. rt6_release()
The IPv6 FIB is protected by rwlock now.
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