[PATCH v2 3/6] block: convert bdrv_graph_wrlock() to AIO_WAIT_WHILE_UNLOCKED()

[Stefan Hajnoczi]

The following conversion is safe and does not change behavior:

 GLOBAL_STATE_CODE();
 ...
  -  AIO_WAIT_WHILE(qemu_get_aio_context(), ...);
  +  AIO_WAIT_WHILE_UNLOCKED(NULL, ...);

Since we're in GLOBAL_STATE_CODE(), qemu_get_aio_context() is our home
thread's AioContext. Thus AIO_WAIT_WHILE() does not unlock the
AioContext:

  if (ctx_ && in_aio_context_home_thread(ctx_)) {\
  while ((cond)) {   \
  aio_poll(ctx_, true);  \
  waited_ = true;\
  }  \

And that means AIO_WAIT_WHILE_UNLOCKED(NULL, ...) can be substituted.

Reviewed-by: Philippe Mathieu-Daudé 
Tested-by: Philippe Mathieu-Daudé 
Reviewed-by: Kevin Wolf 
Signed-off-by: Stefan Hajnoczi 
---
 block/graph-lock.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/block/graph-lock.c b/block/graph-lock.c
index 454c31e691..639526608f 100644
--- a/block/graph-lock.c
+++ b/block/graph-lock.c
@@ -127,7 +127,7 @@ void bdrv_graph_wrlock(void)
  * reader lock.
  */
 qatomic_set(&has_writer, 0);
-AIO_WAIT_WHILE(qemu_get_aio_context(), reader_count() >= 1);
+AIO_WAIT_WHILE_UNLOCKED(NULL, reader_count() >= 1);
 qatomic_set(&has_writer, 1);
 
 /*
-- 
2.39.2

Re: [PATCH v2 3/6] block: convert bdrv_graph_wrlock() to AIO_WAIT_WHILE_UNLOCKED()

[Wilfred Mallawa]

On Thu, 2023-03-09 at 14:08 -0500, Stefan Hajnoczi wrote:
> The following conversion is safe and does not change behavior:
> 
>  GLOBAL_STATE_CODE();
>  ...
>   -  AIO_WAIT_WHILE(qemu_get_aio_context(), ...);
>   +  AIO_WAIT_WHILE_UNLOCKED(NULL, ...);
> 
> Since we're in GLOBAL_STATE_CODE(), qemu_get_aio_context() is our
> home
> thread's AioContext. Thus AIO_WAIT_WHILE() does not unlock the
> AioContext:
> 
>   if (ctx_ && in_aio_context_home_thread(ctx_)) {    \
>   while ((cond)) {   \
>   aio_poll(ctx_, true);  \
>   waited_ = true;    \
>   }  \
> 
> And that means AIO_WAIT_WHILE_UNLOCKED(NULL, ...) can be substituted.
> 
> Reviewed-by: Philippe Mathieu-Daudé 
> Tested-by: Philippe Mathieu-Daudé 
> Reviewed-by: Kevin Wolf 
> Signed-off-by: Stefan Hajnoczi 
> ---
>  block/graph-lock.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
Reviewed-by: Wilfred Mallawa 
> 
> diff --git a/block/graph-lock.c b/block/graph-lock.c
> index 454c31e691..639526608f 100644
> --- a/block/graph-lock.c
> +++ b/block/graph-lock.c
> @@ -127,7 +127,7 @@ void bdrv_graph_wrlock(void)
>   * reader lock.
>   */
>  qatomic_set(&has_writer, 0);
> -    AIO_WAIT_WHILE(qemu_get_aio_context(), reader_count() >= 1);
> +    AIO_WAIT_WHILE_UNLOCKED(NULL, reader_count() >= 1);
>  qatomic_set(&has_writer, 1);
>  
>  /*