Re: [PATCH v13 02/13] eventfd: Export eventfd_wake_count to modules

[Jason Wang]

在 2021/8/31 下午6:36, Xie Yongji 写道:
> 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@xxxxxxxxxxxxx>


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@xxxxxxxxxx>


> ---
>   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);
>