[PATCH] cpus-common: stop using mb_set/mb_read

[PATCH] cpus-common: stop using mb_set/mb_read

[Paolo Bonzini]

Use a store-release at the end of the work item, and a load-acquire when
waiting for the item to be completed.  This is the standard message passing
pattern and is both enough and clearer than mb_read/mb_set.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 cpus-common.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/cpus-common.c b/cpus-common.c
index b0047e456f93..a53716deb437 100644
--- a/cpus-common.c
+++ b/cpus-common.c
@@ -157,7 +157,7 @@ void do_run_on_cpu(CPUState *cpu, run_on_cpu_func func, run_on_cpu_data data,
     wi.exclusive = false;
 
     queue_work_on_cpu(cpu, &wi);
-    while (!qatomic_mb_read(&wi.done)) {
+    while (!qatomic_load_acquire(&wi.done)) {
         CPUState *self_cpu = current_cpu;
 
         qemu_cond_wait(&qemu_work_cond, mutex);
@@ -363,7 +363,7 @@ void process_queued_cpu_work(CPUState *cpu)
         if (wi->free) {
             g_free(wi);
         } else {
-            qatomic_mb_set(&wi->done, true);
+            qatomic_store_release(&wi->done, true);
         }
     }
     qemu_mutex_unlock(&cpu->work_mutex);
-- 
2.40.0

Re: [PATCH] cpus-common: stop using mb_set/mb_read

[Richard Henderson]

On 4/28/23 11:17, Paolo Bonzini wrote:
> Use a store-release at the end of the work item, and a load-acquire when
> waiting for the item to be completed.  This is the standard message passing
> pattern and is both enough and clearer than mb_read/mb_set.
> 
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>

r~

>   cpus-common.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/cpus-common.c b/cpus-common.c
> index b0047e456f93..a53716deb437 100644
> --- a/cpus-common.c
> +++ b/cpus-common.c
> @@ -157,7 +157,7 @@ void do_run_on_cpu(CPUState *cpu, run_on_cpu_func func, run_on_cpu_data data,
>       wi.exclusive = false;
>   
>       queue_work_on_cpu(cpu, &wi);
> -    while (!qatomic_mb_read(&wi.done)) {
> +    while (!qatomic_load_acquire(&wi.done)) {
>           CPUState *self_cpu = current_cpu;
>   
>           qemu_cond_wait(&qemu_work_cond, mutex);
> @@ -363,7 +363,7 @@ void process_queued_cpu_work(CPUState *cpu)
>           if (wi->free) {
>               g_free(wi);
>           } else {
> -            qatomic_mb_set(&wi->done, true);
> +            qatomic_store_release(&wi->done, true);
>           }
>       }
>       qemu_mutex_unlock(&cpu->work_mutex);