diff options
author | Alex Shi <alex.shi@linaro.org> | 2017-10-04 12:03:49 +0800 |
---|---|---|
committer | Alex Shi <alex.shi@linaro.org> | 2017-10-04 12:03:49 +0800 |
commit | a38b2dd146c0bba28633fe857f0c4626e0c691cc (patch) | |
tree | 2d81121c3690a36a3679bc78552067eee74c2c81 /net/netfilter/nf_conntrack_core.c | |
parent | 7ecc9777c5c76d7b31c376ffd4f59c4a85472a1b (diff) | |
parent | d59dabdc4cb380b79c965af28cd4ba001f04834b (diff) |
Merge tag 'v4.9.52' into linux-linaro-lsk-v4.9lsk-v4.9-17.09
This is the 4.9.52 stable release
Diffstat (limited to 'net/netfilter/nf_conntrack_core.c')
-rw-r--r-- | net/netfilter/nf_conntrack_core.c | 52 |
1 files changed, 29 insertions, 23 deletions
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c index 6bd150882ba4..ed9ce7c63252 100644 --- a/net/netfilter/nf_conntrack_core.c +++ b/net/netfilter/nf_conntrack_core.c @@ -95,19 +95,26 @@ static struct conntrack_gc_work conntrack_gc_work; void nf_conntrack_lock(spinlock_t *lock) __acquires(lock) { + /* 1) Acquire the lock */ spin_lock(lock); - while (unlikely(nf_conntrack_locks_all)) { - spin_unlock(lock); - /* - * Order the 'nf_conntrack_locks_all' load vs. the - * spin_unlock_wait() loads below, to ensure - * that 'nf_conntrack_locks_all_lock' is indeed held: - */ - smp_rmb(); /* spin_lock(&nf_conntrack_locks_all_lock) */ - spin_unlock_wait(&nf_conntrack_locks_all_lock); - spin_lock(lock); - } + /* 2) read nf_conntrack_locks_all, with ACQUIRE semantics + * It pairs with the smp_store_release() in nf_conntrack_all_unlock() + */ + if (likely(smp_load_acquire(&nf_conntrack_locks_all) == false)) + return; + + /* fast path failed, unlock */ + spin_unlock(lock); + + /* Slow path 1) get global lock */ + spin_lock(&nf_conntrack_locks_all_lock); + + /* Slow path 2) get the lock we want */ + spin_lock(lock); + + /* Slow path 3) release the global lock */ + spin_unlock(&nf_conntrack_locks_all_lock); } EXPORT_SYMBOL_GPL(nf_conntrack_lock); @@ -148,28 +155,27 @@ static void nf_conntrack_all_lock(void) int i; spin_lock(&nf_conntrack_locks_all_lock); - nf_conntrack_locks_all = true; - /* - * Order the above store of 'nf_conntrack_locks_all' against - * the spin_unlock_wait() loads below, such that if - * nf_conntrack_lock() observes 'nf_conntrack_locks_all' - * we must observe nf_conntrack_locks[] held: - */ - smp_mb(); /* spin_lock(&nf_conntrack_locks_all_lock) */ + nf_conntrack_locks_all = true; for (i = 0; i < CONNTRACK_LOCKS; i++) { - spin_unlock_wait(&nf_conntrack_locks[i]); + spin_lock(&nf_conntrack_locks[i]); + + /* This spin_unlock provides the "release" to ensure that + * nf_conntrack_locks_all==true is visible to everyone that + * acquired spin_lock(&nf_conntrack_locks[]). + */ + spin_unlock(&nf_conntrack_locks[i]); } } static void nf_conntrack_all_unlock(void) { - /* - * All prior stores must be complete before we clear + /* All prior stores must be complete before we clear * 'nf_conntrack_locks_all'. Otherwise nf_conntrack_lock() * might observe the false value but not the entire - * critical section: + * critical section. + * It pairs with the smp_load_acquire() in nf_conntrack_lock() */ smp_store_release(&nf_conntrack_locks_all, false); spin_unlock(&nf_conntrack_locks_all_lock); |