Re: [patch] epoll - send POLLHUP on ->release

[Gregory Haskins]

Davide Libenzi wrote:
> The following patch allows waiters to be notified about the eventfd file* 
> going away, and give them a change to unregister from the wait queue.
> This is turn allows eventfd users to use the eventfd file* w/out 
> holding a live reference to it.
> After the eventfd user callbacks returns, any usage of the eventfd file* 
> should be dropped. The eventfd user callback can acquire sleepy locks 
> since it is invoked lockless.
>
>
>
> Signed-off-by: Davide Libenzi <davidel@xxxxxxxxxxxxxxx>
>   

Tested-by: Gregory Haskins <ghaskins@xxxxxxxxxx>
>
> - Davide
>
>
> ---
>  fs/eventfd.c |   10 +++++++++-
>  1 file changed, 9 insertions(+), 1 deletion(-)
>
> Index: linux-2.6.mod/fs/eventfd.c
> ===================================================================
> --- linux-2.6.mod.orig/fs/eventfd.c	2009-05-27 12:10:03.000000000 -0700
> +++ linux-2.6.mod/fs/eventfd.c	2009-05-27 12:16:57.000000000 -0700
> @@ -59,7 +59,15 @@ int eventfd_signal(struct file *file, in
>  
>  static int eventfd_release(struct inode *inode, struct file *file)
>  {
> -	kfree(file->private_data);
> +	struct eventfd_ctx *ctx = file->private_data;
> +
> +	/*
> +	 * No need to hold the lock here, since we are on the file cleanup
> +	 * path and the ones still attached to the wait queue will be
> +	 * serialized by wake_up_locked_poll().
> +	 */
> +	wake_up_locked_poll(&ctx->wqh, POLLHUP);
> +	kfree(ctx);
>  	return 0;
>  }
>  
>

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