Messages in this thread | | | Date | Thu, 1 Sep 2016 10:11:46 +0200 | From | Sebastian Andrzej Siewior <> | Subject | Re: [RT PATCH 2/2] net: add a lock around icmp_sk() |
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On 2016-08-31 09:37:43 [-0700], Eric Dumazet wrote: > > --- a/net/ipv4/icmp.c > > +++ b/net/ipv4/icmp.c > > @@ -216,12 +219,14 @@ static inline struct sock *icmp_xmit_lock(struct net *net) > > > > local_bh_disable(); > > > > + local_lock(icmp_sk_lock); > > Deadlock alert ? > Please read the comment few lines after, explaining why we have to use > spin_trylock(). > Or maybe I should double check what is local_lock() in RT
On !RT local_lock() is preempt_disable(). On RT local_lock() is a per-CPU sleeping spinlock which can be taken recursively by the owner.
On a "normal" ping reply we have - icmp_reply() - icmp_xmit_lock() - local_lock() - icmp_push_reply() icmp_send() - local_lock()
so that works. I didn't manage to resolve a possible dst_link_failure() path but I would assume it is like the above (where the owner takes the same local_lock() multiple times).
Sebastian
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