Re: [RFC PATCH 0/5] userfaultfd: non-cooperative: syncronous events

[Mike Rapoport <rppt@linux.vnet.ibm.com>]

On Tue, May 16, 2017 at 01:35:57PM +0300, Mike Rapoport wrote:
> Hi,

Any comments on this?
Shall I repost without the "RFC" prefix?
 
> These patches add ability to generate userfaultfd events so that thier
> processing will be synchronized with the non-cooperative thread that caused
> the event.
> 
> In the non-cooperative case userfaultfd resumes execution of the thread
> that caused an event when the notification is read() by the uffd monitor.
> In some cases, like, for example, madvise(MADV_REMOVE), it might be
> desirable to keep the thread that caused the event suspended until the
> uffd monitor had the event handled.
> 
> The first two patches just shuffle the code a bit to make subsequent
> changes easier.
> The patches 3 and 4 create some unification in the way the threads are
> queued into waitqueues either after page fault or after a non-cooperative
> event.
> The fifth patch extends the userfaultfd API with an implementation of
> UFFD_EVENT_REMOVE_SYNC that allows to keep the thread that triggered
> UFFD_EVENT_REMOVE until the uffd monitor would not wake it explicitly.
> 
> Mike Rapoport (5):
>   userfaultfd: introduce userfault_init_waitqueue helper
>   userfaultfd: introduce userfaultfd_should_wait helper
>   userfaultfd: non-cooperative: generalize wake key structure
>   userfaultfd: non-cooperative: use fault_pending_wqh for all events
>   userfaultfd: non-cooperative: allow synchronous EVENT_REMOVE
> 
>  fs/userfaultfd.c                 | 205 ++++++++++++++++++++++++---------------
>  include/uapi/linux/userfaultfd.h |  11 +++
>  2 files changed, 136 insertions(+), 80 deletions(-)
> 
> -- 
> 2.7.4
> 

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