From: Vlad Yasevich <vyasevich@gmail.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Neil Horman <nhorman@tuxdriver.com>,
Sasha Levin <sasha.levin@oracle.com>,
sri@us.ibm.com, "David S. Miller" <davem@davemloft.net>,
linux-sctp@vger.kernel.org, netdev@vger.kernel.org,
Dave Jones <davej@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: sctp: hang in sctp_remaddr_seq_show
Date: Mon, 18 Mar 2013 15:31:06 +0000 [thread overview]
Message-ID: <5147333A.3010907@gmail.com> (raw)
In-Reply-To: <1363620340.29475.132.camel@edumazet-glaptop>
On 03/18/2013 11:25 AM, Eric Dumazet wrote:
> On Mon, 2013-03-18 at 07:04 -0400, Neil Horman wrote:
>
>> I'm not sure why the process would never get back to the schedule, but looking
>> at the sctp_remaddr_seq_show function, I think that we should convert this
>> sequence:
>> sctp_local_bh_disable();
>> read_lock(&head->lock);
>> rcu_read_lock();
>>
>> to this:
>> read_lock(&head->lock);
>> rcu_read_lock_bh();
>>
>> Neil
>
> I dont think so.
>
> BH needs to be disabled before read_lock(&head->lock);
>
> or else, write_lock() could deadlock (assuming it can be called from BH)
>
>
If anything, this should probably be done like this:
rcu_read_lock();
read_lock_bh(&head->lock)
...
read_unlock_bh(&head->lock)
rcu_read_unlock();
-vlad
WARNING: multiple messages have this Message-ID (diff)
From: Vlad Yasevich <vyasevich@gmail.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Neil Horman <nhorman@tuxdriver.com>,
Sasha Levin <sasha.levin@oracle.com>,
sri@us.ibm.com, "David S. Miller" <davem@davemloft.net>,
linux-sctp@vger.kernel.org, netdev@vger.kernel.org,
Dave Jones <davej@redhat.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: sctp: hang in sctp_remaddr_seq_show
Date: Mon, 18 Mar 2013 11:31:06 -0400 [thread overview]
Message-ID: <5147333A.3010907@gmail.com> (raw)
In-Reply-To: <1363620340.29475.132.camel@edumazet-glaptop>
On 03/18/2013 11:25 AM, Eric Dumazet wrote:
> On Mon, 2013-03-18 at 07:04 -0400, Neil Horman wrote:
>
>> I'm not sure why the process would never get back to the schedule, but looking
>> at the sctp_remaddr_seq_show function, I think that we should convert this
>> sequence:
>> sctp_local_bh_disable();
>> read_lock(&head->lock);
>> rcu_read_lock();
>>
>> to this:
>> read_lock(&head->lock);
>> rcu_read_lock_bh();
>>
>> Neil
>
> I dont think so.
>
> BH needs to be disabled before read_lock(&head->lock);
>
> or else, write_lock() could deadlock (assuming it can be called from BH)
>
>
If anything, this should probably be done like this:
rcu_read_lock();
read_lock_bh(&head->lock)
...
read_unlock_bh(&head->lock)
rcu_read_unlock();
-vlad
next prev parent reply other threads:[~2013-03-18 15:31 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-15 16:34 sctp: hang in sctp_remaddr_seq_show Sasha Levin
2013-03-15 16:34 ` Sasha Levin
2013-03-18 11:04 ` Neil Horman
2013-03-18 11:04 ` Neil Horman
2013-03-18 15:25 ` Eric Dumazet
2013-03-18 15:25 ` Eric Dumazet
2013-03-18 15:31 ` Vlad Yasevich [this message]
2013-03-18 15:31 ` Vlad Yasevich
2013-03-18 20:32 ` Neil Horman
2013-03-18 20:32 ` Neil Horman
2013-03-18 20:39 ` Vlad Yasevich
2013-03-18 20:39 ` Vlad Yasevich
2013-03-18 20:48 ` Eric Dumazet
2013-03-18 20:48 ` Eric Dumazet
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