Re: [RFC][PATCH v2] epoll: allow EPOLLWAKEUP flag if PM_SLEEP is enabled

[Rafael J. Wysocki]

On Wednesday, November 13, 2013 02:22:28 AM Amit Pundir wrote:
> ep_create_wakeup_source() reports ENOMEM

That needs to be fixed too.  I suppose we can make the wakeup_source_register()
stub for CONFIG_PM_SLEEP unset return ERR_PTR(-ENOSYS) or something like that
and ep_create_wakeup_source() return that instead of -ENOMEM.  It looks like
eventpoll.c is the only user of it built for CONFIG_PM_SLEEP unset, but that
needs to be double checked.

> if wakeup_source_register()
> returns NULL. ep_create_wakeup_source() assumes that NULL is only
> returned if we run into ENOMEM but NULL is also returned when
> CONFIG_PM_SLEEP is disabled.
> 
> Signed-off-by: Amit Pundir <amit.pundir@xxxxxxxxxx>
> ---
> Changed in v2:
> Using static inline functions instead of #ifdefs
> ---
>  fs/eventpoll.c                 |    3 +--
>  include/uapi/linux/eventpoll.h |   12 ++++++++++++
>  2 files changed, 13 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/eventpoll.c b/fs/eventpoll.c
> index 473e09d..10f9c43 100644
> --- a/fs/eventpoll.c
> +++ b/fs/eventpoll.c
> @@ -1820,8 +1820,7 @@ SYSCALL_DEFINE4(epoll_ctl, int, epfd, int, op, int, fd,
>  		goto error_tgt_fput;
>  
>  	/* Check if EPOLLWAKEUP is allowed */
> -	if ((epds.events & EPOLLWAKEUP) && !capable(CAP_BLOCK_SUSPEND))
> -		epds.events &= ~EPOLLWAKEUP;
> +	ep_epollwakeup_check(&epds.events);

The "check" part of the name kind of suggests that the function will not change
things.  What about ep_adjust_epollwakeup() or something along these lines?

And why don't you pass a pointer to epds to it?  Wouldn't it be cleaner this way?

>  
>  	/*
>  	 * We have to check that the file structure underneath the file descriptor
> diff --git a/include/uapi/linux/eventpoll.h b/include/uapi/linux/eventpoll.h
> index 2c267bc..1d139c2 100644
> --- a/include/uapi/linux/eventpoll.h
> +++ b/include/uapi/linux/eventpoll.h
> @@ -62,4 +62,16 @@ struct epoll_event {
>  } EPOLL_PACKED;
>  
>  
> +#ifdef CONFIG_PM_SLEEP
> +static inline void ep_epollwakeup_check(__u32 *epev)
> +{
> +	if ((*epev & EPOLLWAKEUP) && !capable(CAP_BLOCK_SUSPEND))
> +		*epev &= ~EPOLLWAKEUP;
> +}
> +#else
> +static inline void ep_epollwakeup_check(__u32 *epev)
> +{
> +	*epev &= ~EPOLLWAKEUP;
> +}
> +#endif
>  #endif /* _UAPI_LINUX_EVENTPOLL_H */

Thanks!

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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