Re: [PATCH] thread-pool: signal condition variable while holding lock

["Daniel P. Berrangé" <berrange@redhat.com>]

On Mon, Mar 30, 2026 at 04:01:04PM +0300, Stepan Popov wrote:
> Move qemu_cond_signal() inside the critical section protected by pool->lock.
> Signaling while holding the lock imposes more predictable scheduling behavior.
> 
> Signed-off-by: Stepan Popov <Stepan.Popov@kaspersky.com>
> ---
>  util/thread-pool.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/util/thread-pool.c b/util/thread-pool.c
> index 8f8cb38d5c..8e55aefd07 100644
> --- a/util/thread-pool.c
> +++ b/util/thread-pool.c
> @@ -265,8 +265,8 @@ BlockAIOCB *thread_pool_submit_aio(ThreadPoolFunc *func, void *arg,
>          spawn_thread(pool);
>      }
>      QTAILQ_INSERT_TAIL(&pool->request_list, req, reqs);
> -    qemu_mutex_unlock(&pool->lock);
>      qemu_cond_signal(&pool->request_cond);
> +    qemu_mutex_unlock(&pool->lock);
>      return &req->common;
>  }

Doesn't this order mean that when the signal wakes up the waiting
thread, that thread will get temporarily re-blocked waiting for
'lock' to be released by the original thread too.

With regards,
Daniel
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