diff options
| author | Paolo Bonzini <pbonzini@redhat.com> | 2018-02-16 10:04:18 +0100 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2018-03-12 16:12:47 +0100 |
| commit | c8d3877e48c4f57381d72eaf8d016bff12ce2d7c (patch) | |
| tree | 204fd1c6da69bdfab70ac5e25007c67195d3e78f /include/qemu | |
| parent | 77a8b8462b02a10aea5cad389a8f9260f79ede36 (diff) | |
| download | qemu-c8d3877e48c4f57381d72eaf8d016bff12ce2d7c.tar.gz | |
membarrier: introduce qemu/sys_membarrier.h
This new header file provides heavy-weight "global" memory barriers that
enforce memory ordering on each running thread belonging to the current
process. For now, use a dummy implementation that issues memory barriers
on both sides (matching what QEMU has been doing so far).
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Diffstat (limited to 'include/qemu')
| -rw-r--r-- | include/qemu/rcu.h | 7 | ||||
| -rw-r--r-- | include/qemu/sys_membarrier.h | 17 |
2 files changed, 21 insertions, 3 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 |