From: Vlad Buslov <vladbu@mellanox.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Vlad Buslov <vladbu@mellanox.com>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>,
"jhs@mojatatu.com" <jhs@mojatatu.com>,
"xiyou.wangcong@gmail.com" <xiyou.wangcong@gmail.com>,
"jiri@resnulli.us" <jiri@resnulli.us>,
"davem@davemloft.net" <davem@davemloft.net>
Subject: Re: [PATCH net v2 1/3] net: sched: sch_htb: don't call qdisc_put() while holding tree lock
Date: Fri, 20 Sep 2019 06:34:28 +0000 [thread overview]
Message-ID: <vbfsgorzdam.fsf@mellanox.com> (raw)
In-Reply-To: <66e68933-a553-e078-b92b-6f629c740328@gmail.com>
On Fri 20 Sep 2019 at 01:49, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On 9/19/19 1:14 PM, Vlad Buslov wrote:
>> Recent changes that removed rtnl dependency from rules update path of tc
>> also made tcf_block_put() function sleeping. This function is called from
>> ops->destroy() of several Qdisc implementations, which in turn is called by
>> qdisc_put(). Some Qdiscs call qdisc_put() while holding sch tree spinlock,
>> which results sleeping-while-atomic BUG.
>>
>
>
> Note that calling qdisc_put() while holding sch tree lock can also
> trigger deadlocks.
>
> For example sch_pie.c has a del_timer_sync() in pie_destroy(),
> while the pie_timer() timer handler acquires the root_lock.
>
> (there are other cases like that, SFQ for example)
These and other examples of sleeping calls in cls APIs used by
tcf_block_put() that I described in one of my previous emails make me
think that putting might_sleep() at the beginning of qdisc_put() would
be a good idea, instead of waiting for syzbot to find correct
combination to trigger a crash.
next prev parent reply other threads:[~2019-09-20 6:34 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-19 20:14 [PATCH net v2 0/3] Fix Qdisc destroy issues caused by adding fine-grained locking to filter API Vlad Buslov
2019-09-19 20:14 ` [PATCH net v2 1/3] net: sched: sch_htb: don't call qdisc_put() while holding tree lock Vlad Buslov
2019-09-19 22:49 ` Eric Dumazet
2019-09-20 6:34 ` Vlad Buslov [this message]
2019-09-20 1:05 ` Cong Wang
2019-09-20 6:27 ` Vlad Buslov
2019-09-20 16:53 ` Cong Wang
2019-09-19 20:14 ` [PATCH net v2 2/3] net: sched: multiq: " Vlad Buslov
2019-09-19 20:14 ` [PATCH net v2 3/3] net: sched: sch_sfb: " Vlad Buslov
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