diff options
Diffstat (limited to 'include/qemu/rcu.h')
| -rw-r--r-- | include/qemu/rcu.h | 16 |
1 files changed, 14 insertions, 2 deletions
diff --git a/include/qemu/rcu.h b/include/qemu/rcu.h index f19413d649..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" { @@ -79,7 +80,10 @@ static inline void rcu_read_lock(void) } ctr = atomic_read(&rcu_gp_ctr); - atomic_xchg(&p_rcu_reader->ctr, ctr); + atomic_set(&p_rcu_reader->ctr, ctr); + + /* Write p_rcu_reader->ctr before reading RCU-protected pointers. */ + smp_mb_placeholder(); } static inline void rcu_read_unlock(void) @@ -91,7 +95,15 @@ static inline void rcu_read_unlock(void) return; } - atomic_xchg(&p_rcu_reader->ctr, 0); + /* Ensure that the critical section is seen to precede the + * store to p_rcu_reader->ctr. Together with the following + * 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_placeholder(); if (unlikely(atomic_read(&p_rcu_reader->waiting))) { atomic_set(&p_rcu_reader->waiting, false); qemu_event_set(&rcu_gp_event); |