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authorLinus Torvalds <torvalds@linux-foundation.org>2017-09-04 08:13:52 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2017-09-04 08:13:52 -0700
commit0081a0ce809b611c1f37da5d6ae5bc8027ffd1c4 (patch)
tree600b4fc3b74d5142fe4a2c2f72d934e6204ca432 /net/netfilter
parentfea1543760351e10e9c573ddf8861c2f23f5b866 (diff)
parent94edf6f3c20c9c8ee301bde04150a91bab4bf32c (diff)
Merge branch 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU updates from Ingo Molnad: "The main RCU related changes in this cycle were: - Removal of spin_unlock_wait() - SRCU updates - RCU torture-test updates - RCU Documentation updates - Extend the sys_membarrier() ABI with the MEMBARRIER_CMD_PRIVATE_EXPEDITED variant - Miscellaneous RCU fixes - CPU-hotplug fixes" * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (63 commits) arch: Remove spin_unlock_wait() arch-specific definitions locking: Remove spin_unlock_wait() generic definitions drivers/ata: Replace spin_unlock_wait() with lock/unlock pair ipc: Replace spin_unlock_wait() with lock/unlock pair exit: Replace spin_unlock_wait() with lock/unlock pair completion: Replace spin_unlock_wait() with lock/unlock pair doc: Set down RCU's scheduling-clock-interrupt needs doc: No longer allowed to use rcu_dereference on non-pointers doc: Add RCU files to docbook-generation files doc: Update memory-barriers.txt for read-to-write dependencies doc: Update RCU documentation membarrier: Provide expedited private command rcu: Remove exports from rcu_idle_exit() and rcu_idle_enter() rcu: Add warning to rcu_idle_enter() for irqs enabled rcu: Make rcu_idle_enter() rely on callers disabling irqs rcu: Add assertions verifying blocked-tasks list rcu/tracing: Set disable_rcu_irq_enter on rcu_eqs_exit() rcu: Add TPS() protection for _rcu_barrier_trace strings rcu: Use idle versions of swait to make idle-hack clear swait: Add idle variants which don't contribute to load average ...
Diffstat (limited to 'net/netfilter')
-rw-r--r--net/netfilter/nf_conntrack_core.c52
1 files changed, 29 insertions, 23 deletions
diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
index 9979f46c81dc..51390febd5e3 100644
--- a/net/netfilter/nf_conntrack_core.c
+++ b/net/netfilter/nf_conntrack_core.c
@@ -96,19 +96,26 @@ 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);
@@ -149,28 +156,27 @@ 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);