From: Qian Cai <cai@lca.pw>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: davem@davemloft.net, kuznet@ms2.inr.ac.ru,
yoshfuji@linux-ipv6.org, kuba@kernel.org, netdev@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] ipv4: fix a RCU-list lock in fib_triestat_seq_show
Date: Wed, 25 Mar 2020 13:34:46 -0400 [thread overview]
Message-ID: <92C7474D-4592-44BF-B0ED-26253196511E@lca.pw> (raw)
In-Reply-To: <5e2ed86a-23bc-d3e5-05ad-4e7ed147539c@gmail.com>
> On Mar 25, 2020, at 12:13 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
>
> I would prefer :
>
> diff --git a/net/ipv4/fib_trie.c b/net/ipv4/fib_trie.c
> index ff0c24371e3309b3068980f46d1ed743337d2a3e..4b98ffb27136d3b43f179d6b1b42fe84586acc06 100644
> --- a/net/ipv4/fib_trie.c
> +++ b/net/ipv4/fib_trie.c
> @@ -2581,6 +2581,7 @@ static int fib_triestat_seq_show(struct seq_file *seq, void *v)
> struct hlist_head *head = &net->ipv4.fib_table_hash[h];
> struct fib_table *tb;
>
> + rcu_read_lock();
> hlist_for_each_entry_rcu(tb, head, tb_hlist) {
> struct trie *t = (struct trie *) tb->tb_data;
> struct trie_stat stat;
> @@ -2596,6 +2597,7 @@ static int fib_triestat_seq_show(struct seq_file *seq, void *v)
> trie_show_usage(seq, t->stats);
> #endif
> }
> + rcu_read_unlock();
> }
>
> return 0;
I have no strong opinion either way. My initial thought was to save 255 extra lock/unlock with a single lock/unlock, but I am not sure how time-consuming for each iteration of the outer loop could be. If it could take a bit too long, it does make a lot of sense to reduce the critical section.
next prev parent reply other threads:[~2020-03-25 17:34 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-03-25 15:55 [PATCH] ipv4: fix a RCU-list lock in fib_triestat_seq_show Qian Cai
2020-03-25 16:13 ` Eric Dumazet
2020-03-25 17:34 ` Qian Cai [this message]
2020-03-25 18:31 ` Eric Dumazet
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