linux-kernel - Re: [PATCH] epoll: Add a flag, EPOLLWAKEUP, to prevent suspend while epoll events are ready

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Date:	Wed, 18 Jul 2012 08:41:37 +0200
From:	"Michael Kerrisk (man-pages)" <mtk.manpages@...il.com>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Arve Hjønnevåg <arve@...roid.com>,
	NeilBrown <neilb@...e.de>,
	Linux PM list <linux-pm@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Magnus Damm <magnus.damm@...il.com>, markgross@...gnar.org,
	Matthew Garrett <mjg@...hat.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	John Stultz <john.stultz@...aro.org>,
	Brian Swetland <swetland@...gle.com>,
	Alan Stern <stern@...land.harvard.edu>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>, mtk@....net
Subject: Re: [PATCH] epoll: Add a flag, EPOLLWAKEUP, to prevent suspend while
 epoll events are ready

On Tue, Jul 17, 2012 at 9:22 PM, Rafael J. Wysocki <rjw@...k.pl> wrote:

[...]

> I'm going to push your patch for v3.5,

Thanks.

> but then I'm considering the following
> one for v3.6.  I wouldn't like to make more changes in v3.5-rc at this point,

Acked-by: Michael Kerrisk <mtk.man-pages@...il.com>

Thanks,

Michael

> ---
> From: Rafael J. Wysocki <rjw@...k.pl>
> Subject: PM / Sleep: Require CAP_BLOCK_SUSPEND to use wake_lock/wake_unlock
>
> Require processes wanting to use the wake_lock/wake_unlock sysfs
> files to have the CAP_BLOCK_SUSPEND capability, which also is
> required for the eventpoll EPOLLWAKEUP flag to be effective, so that
> all interfaces related to blocking autosleep depend on the same
> capability.
>
> Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> ---
>  kernel/power/wakelock.c |    7 +++++++
>  1 file changed, 7 insertions(+)
>
> Index: linux/kernel/power/wakelock.c
> ===================================================================
> --- linux.orig/kernel/power/wakelock.c
> +++ linux/kernel/power/wakelock.c
> @@ -9,6 +9,7 @@
>   * manipulate wakelocks on Android.
>   */
>
> +#include <linux/capability.h>
>  #include <linux/ctype.h>
>  #include <linux/device.h>
>  #include <linux/err.h>
> @@ -188,6 +189,9 @@ int pm_wake_lock(const char *buf)
>         size_t len;
>         int ret = 0;
>
> +       if (!capable(CAP_BLOCK_SUSPEND))
> +               return -EPERM;
> +
>         while (*str && !isspace(*str))
>                 str++;
>
> @@ -231,6 +235,9 @@ int pm_wake_unlock(const char *buf)
>         size_t len;
>         int ret = 0;
>
> +       if (!capable(CAP_BLOCK_SUSPEND))
> +               return -EPERM;
> +
>         len = strlen(buf);
>         if (!len)
>                 return -EINVAL;



-- 
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Author of "The Linux Programming Interface"; http://man7.org/tlpi/
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