Le vendredi 03 décembre 2010 à 07:32 +0100, Eric Dumazet a écrit : > Le mercredi 01 décembre 2010 à 10:18 -0800, David Miller a écrit : > > > However, I think it's still valuable to write a few JIT compilers for > > the existing BPF stuff. I considered working on a sparc64 JIT just to > > see what it would look like. > > > > If people work on the BPF optimizer and BPF JITs in parallel, we'll have > > both ready at the same time. win++ > > I began work on implementing a BPF JIT for x86_64 > > My plan is to use external helpers to load skb data/metadata, to keep > BPF program very short and have no dependencies against struct layouts. > > These helpers would be the three load_word, load_half, load_byte. > > In case the bits are in skb head, these helpers should be fast. > > For practical reasons, they would be in ASM for their fast path, and C > for the slow path. They are ASM because they are able to perform the > shortcut (in case of error, doing the stack unwind to perform the > "return 0;") so that we dont have to test their return from the JIT > program. > >
While working on this, I found an annoying problem with current code. This patch is a stable candidate. Thanks [PATCH] filter: fix sk_filter rcu handling Pavel Emelyanov tried to fix a race between sk_filter_(de|at)tach and sk_clone() in commit 47e958eac280c263397 Problem is we can have several clones sharing a common sk_filter, and these clones might want to sk_filter_attach() their own filters at the same time, and can overwrite old_filter->rcu, corrupting RCU queues. We can not use filter->rcu without being sure no other thread could do the same thing. Switch code to a more conventional ref-counting technique : Do the atomic decrement immediately and queue one rcu call back when last reference is released. Signed-off-by: Eric Dumazet <[email protected]> Cc: Pavel Emelyanov <[email protected]> Cc: Paul E. McKenney <[email protected]> Cc: [email protected] --- include/net/sock.h | 4 +++- net/core/filter.c | 19 ++++++------------- 2 files changed, 9 insertions(+), 14 deletions(-) diff --git a/include/net/sock.h b/include/net/sock.h index a6338d0..4308af7 100644 --- a/include/net/sock.h +++ b/include/net/sock.h @@ -1155,6 +1155,8 @@ extern void sk_common_release(struct sock *sk); /* Initialise core socket variables */ extern void sock_init_data(struct socket *sock, struct sock *sk); +extern void sk_filter_release_rcu(struct rcu_head *rcu); + /** * sk_filter_release - release a socket filter * @fp: filter to remove @@ -1165,7 +1167,7 @@ extern void sock_init_data(struct socket *sock, struct sock *sk); static inline void sk_filter_release(struct sk_filter *fp) { if (atomic_dec_and_test(&fp->refcnt)) - kfree(fp); + call_rcu_bh(&fp->rcu, sk_filter_release_rcu); } static inline void sk_filter_uncharge(struct sock *sk, struct sk_filter *fp) diff --git a/net/core/filter.c b/net/core/filter.c index c1ee800..ae21a0d 100644 --- a/net/core/filter.c +++ b/net/core/filter.c @@ -589,23 +589,16 @@ int sk_chk_filter(struct sock_filter *filter, int flen) EXPORT_SYMBOL(sk_chk_filter); /** - * sk_filter_rcu_release - Release a socket filter by rcu_head + * sk_filter_release_rcu - Release a socket filter by rcu_head * @rcu: rcu_head that contains the sk_filter to free */ -static void sk_filter_rcu_release(struct rcu_head *rcu) +void sk_filter_release_rcu(struct rcu_head *rcu) { struct sk_filter *fp = container_of(rcu, struct sk_filter, rcu); - sk_filter_release(fp); -} - -static void sk_filter_delayed_uncharge(struct sock *sk, struct sk_filter *fp) -{ - unsigned int size = sk_filter_len(fp); - - atomic_sub(size, &sk->sk_omem_alloc); - call_rcu_bh(&fp->rcu, sk_filter_rcu_release); + kfree(fp); } +EXPORT_SYMBOL(sk_filter_release_rcu); /** * sk_attach_filter - attach a socket filter @@ -649,7 +642,7 @@ int sk_attach_filter(struct sock_fprog *fprog, struct sock *sk) rcu_assign_pointer(sk->sk_filter, fp); if (old_fp) - sk_filter_delayed_uncharge(sk, old_fp); + sk_filter_uncharge(sk, old_fp); return 0; } EXPORT_SYMBOL_GPL(sk_attach_filter); @@ -663,7 +656,7 @@ int sk_detach_filter(struct sock *sk) sock_owned_by_user(sk)); if (filter) { rcu_assign_pointer(sk->sk_filter, NULL); - sk_filter_delayed_uncharge(sk, filter); + sk_filter_uncharge(sk, filter); ret = 0; } return ret; _______________________________________________ stable mailing list [email protected] http://linux.kernel.org/mailman/listinfo/stable
