[Qemu-devel] [PATCH 07/14] aio-wait: Increase num_waiters even in home thread

Kevin Wolf posted 14 patches 7 years, 1 month ago
There is a newer version of this series
[Qemu-devel] [PATCH 07/14] aio-wait: Increase num_waiters even in home thread
Posted by Kevin Wolf 7 years, 1 month ago
Even if AIO_WAIT_WHILE() is called in the home context of the
AioContext, we still want to allow the condition to change depending on
other threads as long as they kick the AioWait. Specfically block jobs
can be running in an I/O thread and should then be able to kick a drain
in the main loop context.

Signed-off-by: Kevin Wolf <kwolf@redhat.com>
---
 include/block/aio-wait.h | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/include/block/aio-wait.h b/include/block/aio-wait.h
index c85a62f798..46ba7f9111 100644
--- a/include/block/aio-wait.h
+++ b/include/block/aio-wait.h
@@ -77,10 +77,12 @@ typedef struct {
     AioWait *wait_ = (wait);                                       \
     AioContext *ctx_ = (ctx);                                      \
     if (ctx_ && in_aio_context_home_thread(ctx_)) {                \
+        atomic_inc(&wait_->num_waiters);                           \
         while ((cond)) {                                           \
             aio_poll(ctx_, true);                                  \
             waited_ = true;                                        \
         }                                                          \
+        atomic_dec(&wait_->num_waiters);                           \
     } else {                                                       \
         assert(qemu_get_current_aio_context() ==                   \
                qemu_get_aio_context());                            \
-- 
2.13.6


Re: [Qemu-devel] [PATCH 07/14] aio-wait: Increase num_waiters even in home thread
Posted by Fam Zheng 7 years, 1 month ago
On Fri, 09/07 18:15, Kevin Wolf wrote:
> Even if AIO_WAIT_WHILE() is called in the home context of the
> AioContext, we still want to allow the condition to change depending on
> other threads as long as they kick the AioWait. Specfically block jobs
> can be running in an I/O thread and should then be able to kick a drain
> in the main loop context.

We can now move the atomic_inc/atomic_dec pair outside the if/else block,
but that's cosmetic.

Reviewed-by: Fam Zheng <famz@redhat.com>


> 
> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
> ---
>  include/block/aio-wait.h | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/include/block/aio-wait.h b/include/block/aio-wait.h
> index c85a62f798..46ba7f9111 100644
> --- a/include/block/aio-wait.h
> +++ b/include/block/aio-wait.h
> @@ -77,10 +77,12 @@ typedef struct {
>      AioWait *wait_ = (wait);                                       \
>      AioContext *ctx_ = (ctx);                                      \
>      if (ctx_ && in_aio_context_home_thread(ctx_)) {                \
> +        atomic_inc(&wait_->num_waiters);                           \
>          while ((cond)) {                                           \
>              aio_poll(ctx_, true);                                  \
>              waited_ = true;                                        \
>          }                                                          \
> +        atomic_dec(&wait_->num_waiters);                           \
>      } else {                                                       \
>          assert(qemu_get_current_aio_context() ==                   \
>                 qemu_get_aio_context());                            \
> -- 
> 2.13.6
>