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SubjectRe: [RFC][PATCH v2] epoll: allow EPOLLWAKEUP flag if PM_SLEEP is enabled
On 14 November 2013 03:14, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> On Wednesday, November 13, 2013 01:35:38 PM Amit Pundir wrote:
>> On 13 November 2013 05:29, Rafael J. Wysocki <rjw@sisk.pl> wrote:
>> > 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.
>>
>> Instead of modifying wakeup_source_register() stub, what if I make
>> ep_create_wakeup_source() static inline as well and use its stub to
>> return -ENOSYS when CONFIG_PM_SLEEP is not set?
>> ep_create_wakeup_source() is used only in fs/eventpoll.c anyway.
>
> Well, you can do that too.
>

On second thought we may skip modifying ep_create_wakeup_source() or
wakeup_source_register() altogether because once we drop EPOLLWAKEUP
from epoll events mask(if PM_SLEEP is unset) then I don't see us
running into ep_create_wakeup_source() again. And the only reason for
ep_create_wakeup_source() failure will be -ENOMEM as far as I can see.

>> >> 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@linaro.org>
>> >> ---
>> >> 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?
>>
>> I see couple of ep_set_* functions in eventpoll.c. Does it make sense
>> to have something like ep_set_epollwakeup()?
>
> This particular one doesn't really set anything. I suppose that a name like
> "ep_take_care_of_epollwakeup" might be somewhat closer to what it really does ...

I'm running out of ideas on this one, lets go with
"ep_take_care_of_epollwakeup".

Regards,
Amit Pundir

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


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