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From: David Miller <davem@davemloft.net>
To: herbert@gondor.apana.org.au
Cc: edumazet@google.com, netdev@vger.kernel.org,
	eric.dumazet@gmail.com, syzkaller@googlegroups.com
Subject: Re: [PATCH] inet: frags: Remove unnecessary smp_store_release/READ_ONCE
Date: Thu, 30 May 2019 11:51:54 -0700 (PDT)	[thread overview]
Message-ID: <20190530.115154.102635044166921930.davem@davemloft.net> (raw)
In-Reply-To: <20190529054026.fwcyhzt33dshma4h@gondor.apana.org.au>

From: Herbert Xu <herbert@gondor.apana.org.au>
Date: Wed, 29 May 2019 13:40:26 +0800

> The smp_store_release call in fqdir_exit cannot protect the setting
> of fqdir->dead as claimed because its memory barrier is only
> guaranteed to be one-way and the barrier precedes the setting of
> fqdir->dead.
> 
> IOW it doesn't provide any barriers between fq->dir and the following
> hash table destruction.
> 
> In fact, the code is safe anyway because call_rcu does provide both
> the memory barrier as well as a guarantee that when the destruction
> work starts executing all RCU readers will see the updated value for
> fqdir->dead.
> 
> Therefore this patch removes the unnecessary smp_store_release call
> as well as the corresponding READ_ONCE on the read-side in order to
> not confuse future readers of this code.  Comments have been added
> in their places.
> 
> Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

Applied.

  parent reply	other threads:[~2019-05-30 18:51 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-24 16:03 [PATCH net-next 00/11] inet: frags: avoid possible races at netns dismantle Eric Dumazet
2019-05-24 16:03 ` [PATCH net-next 01/11] inet: rename netns_frags to fqdir Eric Dumazet
2019-05-24 16:03 ` [PATCH net-next 02/11] net: rename inet_frags_exit_net() to fqdir_exit() Eric Dumazet
2019-05-24 16:03 ` [PATCH net-next 03/11] net: rename struct fqdir fields Eric Dumazet
2019-05-24 16:03 ` [PATCH net-next 04/11] ipv4: no longer reference init_net in ip4_frags_ns_ctl_table[] Eric Dumazet
2019-05-24 16:03 ` [PATCH net-next 05/11] ipv6: no longer reference init_net in ip6_frags_ns_ctl_table[] Eric Dumazet
2019-05-24 16:03 ` [PATCH net-next 06/11] netfilter: ipv6: nf_defrag: no longer reference init_net in nf_ct_frag6_sysctl_table Eric Dumazet
2019-05-24 16:03 ` [PATCH net-next 07/11] ieee820154: 6lowpan: no longer reference init_net in lowpan_frags_ns_ctl_table Eric Dumazet
2019-05-24 16:03 ` [PATCH net-next 08/11] net: rename inet_frags_init_net() to fdir_init() Eric Dumazet
2019-05-24 16:03 ` [PATCH net-next 09/11] net: add a net pointer to struct fqdir Eric Dumazet
2019-05-24 16:03 ` [PATCH net-next 10/11] net: dynamically allocate fqdir structures Eric Dumazet
2019-05-24 16:03 ` [PATCH net-next 11/11] inet: frags: rework rhashtable dismantle Eric Dumazet
2019-05-28  6:34   ` Herbert Xu
2019-05-28 13:31     ` Eric Dumazet
2019-05-29  5:40       ` [PATCH] inet: frags: Remove unnecessary smp_store_release/READ_ONCE Herbert Xu
2019-05-29  5:43         ` Dmitry Vyukov
2019-05-29  5:47           ` Herbert Xu
2019-05-31  8:24             ` Dmitry Vyukov
2019-05-31 14:45               ` Herbert Xu
2019-05-31 15:45                 ` Eric Dumazet
2019-05-31 16:29                   ` Andrea Parri
2019-05-31 17:11                     ` Eric Dumazet
2019-06-07 12:06                       ` Dmitry Vyukov
2019-05-31 17:11                   ` Paul E. McKenney
2019-05-31 17:18                     ` Eric Dumazet
2019-05-29 21:30         ` Eric Dumazet
2019-05-30 18:51         ` David Miller [this message]
2019-05-26 21:26 ` [PATCH net-next 00/11] inet: frags: avoid possible races at netns dismantle David Miller

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