linux.git/include/uapi/linux/eventpoll.h, branch v6.18.21

eventpoll: Add epoll ioctl for epoll_params

2024-02-14T11:01:01+00:00

Add an ioctl for getting and setting epoll_params. User programs can use
this ioctl to get and set the busy poll usec time, packet budget, and
prefer busy poll params for a specific epoll context.

Parameters are limited:
  - busy_poll_usecs is limited to <= s32_max
  - busy_poll_budget is limited to <= NAPI_POLL_WEIGHT by unprivileged
    users (!capable(CAP_NET_ADMIN))
  - prefer_busy_poll must be 0 or 1
  - __pad must be 0

Signed-off-by: Joe Damato 
Acked-by: Stanislav Fomichev 
Reviewed-by: Jiri Slaby 
Reviewed-by: Eric Dumazet 
Signed-off-by: David S. Miller

Move ep_take_care_of_epollwakeup() to fs/eventpoll.c

2023-03-10T20:05:16+00:00

This doesn't make any sense to expose to userspace, so it's been moved
to the one user.  This was introduced by commit 95f19f658ce1 ("epoll:
drop EPOLLWAKEUP if PM_SLEEP is disabled").

Signed-off-by: Palmer Dabbelt 
Reviewed-by: Andrew Waterman 
Reviewed-by: Albert Ou 
Message-Id: <1447119071-19392-7-git-send-email-palmer@dabbelt.com>
[thuth: Rebased to fix contextual conflicts]
Reviewed-by: Arnd Bergmann 
Reviewed-by: Christoph Hellwig 
Signed-off-by: Thomas Huth 
Signed-off-by: Arnd Bergmann

eventpoll: add EPOLL_URING_WAKE poll wakeup flag

2022-11-21T14:45:29+00:00

We can have dependencies between epoll and io_uring. Consider an epoll
context, identified by the epfd file descriptor, and an io_uring file
descriptor identified by iofd. If we add iofd to the epfd context, and
arm a multishot poll request for epfd with iofd, then the multishot
poll request will repeatedly trigger and generate events until terminated
by CQ ring overflow. This isn't a desired behavior.

Add EPOLL_URING so that io_uring can pass it in as part of the poll wakeup
key, and io_uring can check for that to detect a potential recursive
invocation.

Cc: stable@vger.kernel.org # 6.0
Signed-off-by: Jens Axboe

eventpoll.h: wrap casts in () properly

2018-07-15T12:03:06+00:00

When importing the latest copy of the kernel headers into Bionic,
Christpher and Elliott noticed that the eventpoll.h casts were not
wrapped in ().  As it is, clang complains about macros without
surrounding (), so this makes it a pain for userspace tools.

So fix it up by adding another () pair, and make them line up purty by
using tabs.

Fixes: 65aaf87b3aa2 ("add EPOLLNVAL, annotate EPOLL... and event_poll->event")
Reported-by: Christopher Ferris 
Reported-by: Elliott Hughes 
Cc: stable 
Cc: Thomas Gleixner 
Cc: Al Viro 
Signed-off-by: Greg Kroah-Hartman

add EPOLLNVAL, annotate EPOLL... and event_poll->event

2018-02-01T21:28:55+00:00

Signed-off-by: Al Viro

License cleanup: add SPDX license identifier to uapi header files with a license

2017-11-02T10:20:11+00:00

Many user space API headers have licensing information, which is either
incomplete, badly formatted or just a shorthand for referring to the
license under which the file is supposed to be.  This makes it hard for
compliance tools to determine the correct license.

Update these files with an SPDX license identifier.  The identifier was
chosen based on the license information in the file.

GPL/LGPL licensed headers get the matching GPL/LGPL SPDX license
identifier with the added 'WITH Linux-syscall-note' exception, which is
the officially assigned exception identifier for the kernel syscall
exception:

   NOTE! This copyright does *not* cover user programs that use kernel
   services by normal system calls - this is merely considered normal use
   of the kernel, and does *not* fall under the heading of "derived work".

This exception makes it possible to include GPL headers into non GPL
code, without confusing license compliance tools.

Headers which have either explicit dual licensing or are just licensed
under a non GPL license are updated with the corresponding SPDX
identifier and the GPLv2 with syscall exception identifier.  The format
is:
        ((GPL-2.0 WITH Linux-syscall-note) OR SPDX-ID-OF-OTHER-LICENSE)

SPDX license identifiers are a legally binding shorthand, which can be
used instead of the full boiler plate text.  The update does not remove
existing license information as this has to be done on a case by case
basis and the copyright holders might have to be consulted. This will
happen in a separate step.

This patch is based on work done by Thomas Gleixner and Kate Stewart and
Philippe Ombredanne.  See the previous patch in this series for the
methodology of how this patch was researched.

Reviewed-by: Kate Stewart 
Reviewed-by: Philippe Ombredanne 
Reviewed-by: Thomas Gleixner 
Signed-off-by: Greg Kroah-Hartman

eventpoll.h: add missing epoll event masks

2017-03-14T01:47:33+00:00

[resend due to me forgetting to cc: linux-api the first time around I
posted these back on Feb 23]

From: Greg Kroah-Hartman 

For some reason these values are not in the uapi header file, so any
libc has to define it themselves.  To prevent them from needing to do
this, just have the kernel provide the correct values.

Reported-by: Elliott Hughes 
Signed-off-by: Greg Kroah-Hartman

eventpoll.h: fix epoll event masks

2017-03-14T01:47:33+00:00

[resend due to me forgetting to cc: linux-api the first time around I
posted these back on Feb 23]

From: Greg Kroah-Hartman 

When userspace tries to use these defines, it complains that it needs to
be an unsigned 1 that is shifted, so libc implementations have to create
their own version.  Fix this by defining it properly so that libcs can
just use the kernel uapi header.

Reported-by: Elliott Hughes 
Signed-off-by: Greg Kroah-Hartman

epoll: add EPOLLEXCLUSIVE flag

2016-01-21T01:09:18+00:00

Currently, epoll file descriptors or epfds (the fd returned from
epoll_create[1]()) that are added to a shared wakeup source are always
added in a non-exclusive manner.  This means that when we have multiple
epfds attached to a shared fd source they are all woken up.  This creates
thundering herd type behavior.

Introduce a new 'EPOLLEXCLUSIVE' flag that can be passed as part of the
'event' argument during an epoll_ctl() EPOLL_CTL_ADD operation.  This new
flag allows for exclusive wakeups when there are multiple epfds attached
to a shared fd event source.

The implementation walks the list of exclusive waiters, and queues an
event to each epfd, until it finds the first waiter that has threads
blocked on it via epoll_wait().  The idea is to search for threads which
are idle and ready to process the wakeup events.  Thus, we queue an event
to at least 1 epfd, but may still potentially queue an event to all epfds
that are attached to the shared fd source.

Performance testing was done by Madars Vitolins using a modified version
of Enduro/X.  The use of the 'EPOLLEXCLUSIVE' flag reduce the length of
this particular workload from 860s down to 24s.

Sample epoll_clt text:

EPOLLEXCLUSIVE

  Sets an exclusive wakeup mode for the epfd file descriptor that is
  being attached to the target file descriptor, fd.  Thus, when an event
  occurs and multiple epfd file descriptors are attached to the same
  target file using EPOLLEXCLUSIVE, one or more epfds will receive an
  event with epoll_wait(2).  The default in this scenario (when
  EPOLLEXCLUSIVE is not set) is for all epfds to receive an event.
  EPOLLEXCLUSIVE may only be specified with the op EPOLL_CTL_ADD.

Signed-off-by: Jason Baron 
Tested-by: Madars Vitolins 
Cc: Ingo Molnar 
Cc: Peter Zijlstra 
Cc: Al Viro 
Cc: Michael Kerrisk 
Cc: Eric Wong 
Cc: Jonathan Corbet 
Cc: Andy Lutomirski 
Cc: Hagen Paul Pfeifer 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

epoll: drop EPOLLWAKEUP if PM_SLEEP is disabled

2013-12-03T14:35:52+00:00

Drop EPOLLWAKEUP from epoll events mask if CONFIG_PM_SLEEP is disabled.

Signed-off-by: Amit Pundir 
Cc: John Stultz 
Cc: Alexander Viro 
Signed-off-by: Rafael J. Wysocki