On Wed, 2016-08-31 at 18:00 +0200, Sebastian Andrzej Siewior wrote:
> It looks like the this_cpu_ptr() access in icmp_sk() is protected with
> local_bh_disable(). To avoid missing serialization in -RT I am adding
> here a local lock. No crash has been observed, this is just precaution.
>
Hmm...
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
> ---
> net/ipv4/icmp.c | 8 ++++++++
> 1 file changed, 8 insertions(+)
>
> diff --git a/net/ipv4/icmp.c b/net/ipv4/icmp.c
> index c1f1d5030d37..63731fd6af3e 100644
> --- a/net/ipv4/icmp.c
> +++ b/net/ipv4/icmp.c
> @@ -78,6 +78,7 @@
> #include <linux/string.h>
> #include <linux/netfilter_ipv4.h>
> #include <linux/slab.h>
> +#include <linux/locallock.h>
> #include <net/snmp.h>
> #include <net/ip.h>
> #include <net/route.h>
> @@ -205,6 +206,8 @@ static const struct icmp_control icmp_pointers[NR_ICMP_TYPES+1];
> *
> * On SMP we have one ICMP socket per-cpu.
> */
> +static DEFINE_LOCAL_IRQ_LOCK(icmp_sk_lock);
> +
> static struct sock *icmp_sk(struct net *net)
> {
> return *this_cpu_ptr(net->ipv4.icmp_sk);
> @@ -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
> sk = icmp_sk(net);
>
> if (unlikely(!spin_trylock(&sk->sk_lock.slock))) {
...
> /* This can happen if the output path signals a
> * dst_link_failure() for an outgoing ICMP packet.
> */
> + local_unlock(icmp_sk_lock);
> local_bh_enable();
> return NULL;
--
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