From: David Miller <davem@davemloft.net>
To: sasha.levin@oracle.com
Cc: tgraf@suug.ch, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org, kaber@trash.net,
paulmck@linux.vnet.ibm.com, josh@joshtriplett.org,
challa@noironetworks.com, walpole@cs.pdx.edu,
dev@openvswitch.org, netfilter-devel@vger.kernel.org,
nikolay@redhat.com
Subject: Re: [PATCH net-next 2/3] netlink: Convert netlink_lookup() to use RCU protected hash table
Date: Mon, 04 Aug 2014 19:58:41 -0700 (PDT) [thread overview]
Message-ID: <20140804.195841.536725238366145203.davem@davemloft.net> (raw)
In-Reply-To: <53E03D0B.3000208@oracle.com>
From: Sasha Levin <sasha.levin@oracle.com>
Date: Mon, 04 Aug 2014 22:10:19 -0400
> On 08/02/2014 05:47 AM, Thomas Graf wrote:
>> static void *netlink_seq_start(struct seq_file *seq, loff_t *pos)
>> - __acquires(nl_table_lock)
>> {
>> - read_lock(&nl_table_lock);
>> + rcu_read_lock();
>> return *pos ? netlink_seq_socket_idx(seq, *pos - 1) : SEQ_START_TOKEN;
>> }
>
> I'm not sure how you expect this code to work. You're replacing a local lock
> with a RCU critical section. Imagine you're doing spin_lock() and just going
> back to userspace.
>
> It's quite easy to trigger this issue:
I think he expected the end of the seq sequence to drop the RCU lock,
via netlink_seq_stop().
next prev parent reply other threads:[~2014-08-05 2:58 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-08-02 9:47 [PATCH net-next v5 0/3] Lockless netlink_lookup() with new concurrent " Thomas Graf
2014-08-02 9:47 ` [PATCH net-next 1/3] lib: Resizable, Scalable, Concurrent Hash Table Thomas Graf
2014-08-02 10:32 ` Nikolay Aleksandrov
2014-08-02 9:47 ` [PATCH net-next 2/3] netlink: Convert netlink_lookup() to use RCU protected hash table Thomas Graf
2014-08-02 10:44 ` Nikolay Aleksandrov
2014-08-05 2:10 ` Sasha Levin
2014-08-05 2:58 ` David Miller [this message]
2014-08-05 5:50 ` Eric Dumazet
2014-08-05 5:58 ` David Miller
2014-08-02 9:47 ` [PATCH net-next 3/3] nftables: Convert nft_hash to use generic rhashtable Thomas Graf
2014-08-02 10:56 ` Nikolay Aleksandrov
2014-08-03 2:53 ` [PATCH net-next v5 0/3] Lockless netlink_lookup() with new concurrent hash table David Miller
-- strict thread matches above, loose matches on Subject: below --
2014-08-01 11:58 [PATCH net-next v4 " Thomas Graf
2014-08-01 11:58 ` [PATCH net-next 2/3] netlink: Convert netlink_lookup() to use RCU protected " Thomas Graf
2014-08-01 14:51 ` Nikolay Aleksandrov
2014-08-01 15:15 ` Thomas Graf
2014-08-01 15:20 ` Nikolay Aleksandrov
2014-08-01 8:51 [PATCH net-next v3 0/3] Lockless netlink_lookup() with new concurrent " Thomas Graf
2014-08-01 8:51 ` [PATCH net-next 2/3] netlink: Convert netlink_lookup() to use RCU protected " Thomas Graf
2014-07-31 22:56 [PATCH v2 0/3 net-next] Lockless netlink_lookup() with new concurrent " Thomas Graf
2014-07-31 22:56 ` [PATCH net-next 2/3] netlink: Convert netlink_lookup() to use RCU protected " Thomas Graf
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