diff options
| -rw-r--r-- | include/qemu/rcu.h | 7 | ||||
| -rw-r--r-- | include/qemu/sys_membarrier.h | 17 | ||||
| -rw-r--r-- | util/rcu.c | 9 |
3 files changed, 26 insertions, 7 deletions
diff --git a/include/qemu/rcu.h b/include/qemu/rcu.h index 625f09ac09..22876d1428 100644 --- a/include/qemu/rcu.h +++ b/include/qemu/rcu.h @@ -27,6 +27,7 @@ #include "qemu/thread.h" #include "qemu/queue.h" #include "qemu/atomic.h" +#include "qemu/sys_membarrier.h" #ifdef __cplusplus extern "C" { @@ -82,7 +83,7 @@ static inline void rcu_read_lock(void) atomic_set(&p_rcu_reader->ctr, ctr); /* Write p_rcu_reader->ctr before reading RCU-protected pointers. */ - smp_mb(); + smp_mb_placeholder(); } static inline void rcu_read_unlock(void) @@ -96,13 +97,13 @@ static inline void rcu_read_unlock(void) /* Ensure that the critical section is seen to precede the * store to p_rcu_reader->ctr. Together with the following - * smp_mb(), this ensures writes to p_rcu_reader->ctr + * smp_mb_placeholder(), this ensures writes to p_rcu_reader->ctr * are sequentially consistent. */ atomic_store_release(&p_rcu_reader->ctr, 0); /* Write p_rcu_reader->ctr before reading p_rcu_reader->waiting. */ - smp_mb(); + smp_mb_placeholder(); if (unlikely(atomic_read(&p_rcu_reader->waiting))) { atomic_set(&p_rcu_reader->waiting, false); qemu_event_set(&rcu_gp_event); diff --git a/include/qemu/sys_membarrier.h b/include/qemu/sys_membarrier.h new file mode 100644 index 0000000000..9ce7f5210b --- /dev/null +++ b/include/qemu/sys_membarrier.h @@ -0,0 +1,17 @@ +/* + * Process-global memory barriers + * + * Copyright (c) 2018 Red Hat, Inc. + * + * Author: Paolo Bonzini <pbonzini@redhat.com> + */ + +#ifndef QEMU_SYS_MEMBARRIER_H +#define QEMU_SYS_MEMBARRIER_H 1 + +/* Keep it simple, execute a real memory barrier on both sides. */ +static inline void smp_mb_global_init(void) {} +#define smp_mb_global() smp_mb() +#define smp_mb_placeholder() smp_mb() + +#endif diff --git a/util/rcu.c b/util/rcu.c index 7366dc50dd..5676c22bd1 100644 --- a/util/rcu.c +++ b/util/rcu.c @@ -93,10 +93,10 @@ static void wait_for_readers(void) } /* Here, order the stores to index->waiting before the loads of - * index->ctr. Pairs with smp_mb() in rcu_read_unlock(), + * index->ctr. Pairs with smp_mb_placeholder() in rcu_read_unlock(), * ensuring that the loads of index->ctr are sequentially consistent. */ - smp_mb(); + smp_mb_global(); QLIST_FOREACH_SAFE(index, ®istry, node, tmp) { if (!rcu_gp_ongoing(&index->ctr)) { @@ -145,9 +145,9 @@ void synchronize_rcu(void) qemu_mutex_lock(&rcu_sync_lock); /* Write RCU-protected pointers before reading p_rcu_reader->ctr. - * Pairs with smp_mb() in rcu_read_lock(). + * Pairs with smp_mb_placeholder() in rcu_read_lock(). */ - smp_mb(); + smp_mb_global(); qemu_mutex_lock(&rcu_registry_lock); if (!QLIST_EMPTY(®istry)) { @@ -376,6 +376,7 @@ static void rcu_init_child(void) static void __attribute__((__constructor__)) rcu_init(void) { + smp_mb_global_init(); #ifdef CONFIG_POSIX pthread_atfork(rcu_init_lock, rcu_init_unlock, rcu_init_child); #endif |