Re: [PATCH v2 3/3] kernel/watch_queue: Remove wqueue->defunct and use pipe for clear check

[Siddh Raman Pant]

On Fri, 05 Aug 2022 12:54:31 +0530  Eric Biggers  wrote:
> Why is the READ_ONCE() needed?  Doesn't wqueue->lock protect wqueue->pipe?

We are changing the pointer while a notification can be potentially waiting to
be posted to the pipe. So a barrier is needed to prevent compiler magic from
reloading the value.

This was remarked by David Howells here:
https://lore.kernel.org/lkml/3558070.1658933200@xxxxxxxxxxxxxxxxxxxxxx/

> This isn't the correct block comment format; it should look like:
> 
>      /*
>       * This pipe will get freed by the caller free_pipe_info().
>       * Removing this reference also prevents new notifications.
>       */
> 
> - Eric
> 

Okay, will make the change.

Thanks,
Siddh