Linux Virtualization - Sep 2021 - [PATCH v13 02/13] eventfd: Export eventfd_wake_count to modules

? 2021/8/31 ??6:36, Xie Yongji ??:
> Export eventfd_wake_count so that some modules can use
> the eventfd_signal_count() to check whether the
> eventfd_signal() call should be deferred to a safe context.
>
> Signed-off-by: Xie Yongji <xieyongji at bytedance.com>

And this matches the comment inside eventfd_signal():

 ??????? /*
 ???????? * Deadlock or stack overflow issues can happen if we recurse here
 ???????? * through waitqueue wakeup handlers. If the caller users 
potentially
 ???????? * nested waitqueues with custom wakeup handlers, then it should
 ???????? * check eventfd_signal_count() before calling this function. If
 ???????? * it returns true, the eventfd_signal() call should be 
deferred to a
 ???????? * safe context.
 ???????? */


So:

Acked-by: Jason Wang <jasowang at redhat.com>

> ---
>   fs/eventfd.c | 1 +
>   1 file changed, 1 insertion(+)
>
> diff --git a/fs/eventfd.c b/fs/eventfd.c
> index e265b6dd4f34..1b3130b8d6c1 100644
> --- a/fs/eventfd.c
> +++ b/fs/eventfd.c
> @@ -26,6 +26,7 @@
>   #include <linux/uio.h>
>   
>   DEFINE_PER_CPU(int, eventfd_wake_count);
> +EXPORT_PER_CPU_SYMBOL_GPL(eventfd_wake_count);
>   
>   static DEFINE_IDA(eventfd_ida);
>