diff options
Diffstat (limited to 'include/qemu')
| -rw-r--r-- | include/qemu/rcu.h | 16 | ||||
| -rw-r--r-- | include/qemu/sys_membarrier.h | 27 | ||||
| -rw-r--r-- | include/qemu/timer.h | 14 |
3 files changed, 55 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); diff --git a/include/qemu/sys_membarrier.h b/include/qemu/sys_membarrier.h new file mode 100644 index 0000000000..316e3dc4a2 --- /dev/null +++ b/include/qemu/sys_membarrier.h @@ -0,0 +1,27 @@ +/* + * 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 + +#ifdef CONFIG_MEMBARRIER +/* Only block reordering at the compiler level in the performance-critical + * side. The slow side forces processor-level ordering on all other cores + * through a system call. + */ +extern void smp_mb_global_init(void); +extern void smp_mb_global(void); +#define smp_mb_placeholder() barrier() +#else +/* 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 + +#endif diff --git a/include/qemu/timer.h b/include/qemu/timer.h index 3b5a54b014..39ea907e65 100644 --- a/include/qemu/timer.h +++ b/include/qemu/timer.h @@ -251,6 +251,20 @@ bool qemu_clock_run_timers(QEMUClockType type); */ bool qemu_clock_run_all_timers(void); +/** + * qemu_clock_get_last: + * + * Returns last clock query time. + */ +uint64_t qemu_clock_get_last(QEMUClockType type); +/** + * qemu_clock_set_last: + * + * Sets last clock query time. + */ +void qemu_clock_set_last(QEMUClockType type, uint64_t last); + + /* * QEMUTimerList */ |