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924f51534d
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Eric Biggers 924f51534d aio: keep poll requests on waitqueue until completed 
commit 363bee27e2 upstream.

Currently, aio_poll_wake() will always remove the poll request from the
waitqueue.  Then, if aio_poll_complete_work() sees that none of the
polled events are ready and the request isn't cancelled, it re-adds the
request to the waitqueue.  (This can easily happen when polling a file
that doesn't pass an event mask when waking up its waitqueue.)

This is fundamentally broken for two reasons:

  1. If a wakeup occurs between vfs_poll() and the request being
     re-added to the waitqueue, it will be missed because the request
     wasn't on the waitqueue at the time.  Therefore, IOCB_CMD_POLL
     might never complete even if the polled file is ready.

  2. When the request isn't on the waitqueue, there is no way to be
     notified that the waitqueue is being freed (which happens when its
     lifetime is shorter than the struct file's).  This is supposed to
     happen via the waitqueue entries being woken up with POLLFREE.

Therefore, leave the requests on the waitqueue until they are actually
completed (or cancelled).  To keep track of when aio_poll_complete_work
needs to be scheduled, use new fields in struct poll_iocb.  Remove the
'done' field which is now redundant.

Note that this is consistent with how sys_poll() and eventpoll work;
their wakeup functions do *not* remove the waitqueue entries.

Fixes: 2c14fa838c ("aio: implement IOCB_CMD_POLL")
Cc: <stable@vger.kernel.org> # v4.18+
Link: https://lore.kernel.org/r/20211209010455.42744-5-ebiggers@kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2021-12-14 10:57:15 +01:00
arch KVM: x86: Wait for IPIs to be delivered when handling Hyper-V TLB flush hypercall 2021-12-14 10:57:11 +01:00
block block: avoid to quiesce queue in elevator_init_mq 2021-12-01 09:04:56 +01:00
certs certs: Add support for using elliptic curve keys for signing modules 2021-08-23 19:55:42 +03:00
crypto crypto: pcrypt - Delay write to padata->info 2021-11-18 19:16:44 +01:00
Documentation docs: accounting: update delay-accounting.rst reference 2021-12-01 09:04:56 +01:00
drivers binder: use wake_up_pollfree() 2021-12-14 10:57:15 +01:00
fs aio: keep poll requests on waitqueue until completed 2021-12-14 10:57:15 +01:00
include wait: add wake_up_pollfree() 2021-12-14 10:57:15 +01:00
init init: make unknown command line param message clearer 2021-11-18 19:17:11 +01:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-11-25 09:48:42 +01:00
kernel wait: add wake_up_pollfree() 2021-12-14 10:57:15 +01:00
lib siphash: use _unaligned version by default 2021-12-08 09:04:47 +01:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
mm mm: bdi: initialize bdi_min_ratio when bdi is unregistered 2021-12-14 10:57:11 +01:00
net net/sched: fq_pie: prevent dismantle issue 2021-12-14 10:57:10 +01:00
samples samples/bpf: Fix incorrect use of strlen in xdp_redirect_cpu 2021-11-25 09:48:33 +01:00
scripts leaking_addresses: Always print a trailing newline 2021-11-18 19:16:16 +01:00
security selinux: fix NULL-pointer dereference when hashtab allocation fails 2021-11-25 09:49:07 +01:00
sound ALSA: pcm: oss: Handle missing errors in snd_pcm_oss_change_params*() 2021-12-14 10:57:12 +01:00
tools selftests: KVM: avoid failures due to reserved HyperTransport region 2021-12-14 10:57:14 +01:00
usr .gitignore: prefix local generated files with a slash 2021-05-02 00:43:35 +09:00
virt KVM: Ensure local memslot copies operate on up-to-date arch-specific data 2021-12-08 09:04:43 +01:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig
.get_maintainer.ignore
.gitattributes .gitattributes: use 'dts' diff driver for dts files 2019-12-04 19:44:11 -08:00
.gitignore .gitignore: ignore only top-level modules.builtin 2021-05-02 00:43:35 +09:00
.mailmap mailmap: add Andrej Shadura 2021-10-18 20:22:03 -10:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS MAINTAINERS: Move Daniel Drake to credits 2021-09-21 08:34:58 +03:00
Kbuild kbuild: rename hostprogs-y/always to hostprogs/always-y 2020-02-04 01:53:07 +09:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS drm fixes for 5.15 final 2021-10-28 12:17:01 -07:00
Makefile Linux 5.15.7 2021-12-08 09:04:57 +01:00
README

README 

Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.