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Waiman Long b3f84e4878 locking/rwsem: Add a new RWSEM_ANONYMOUSLY_OWNED flag 
[ Upstream commit d7d760efad ]

There are use cases where a rwsem can be acquired by one task, but
released by another task. In thess cases, optimistic spinning may need
to be disabled.  One example will be the filesystem freeze/thaw code
where the task that freezes the filesystem will acquire a write lock
on a rwsem and then un-owns it before returning to userspace. Later on,
another task will come along, acquire the ownership, thaw the filesystem
and release the rwsem.

Bit 0 of the owner field was used to designate that it is a reader
owned rwsem. It is now repurposed to mean that the owner of the rwsem
is not known. If only bit 0 is set, the rwsem is reader owned. If bit
0 and other bits are set, it is writer owned with an unknown owner.
One such value for the latter case is (-1L). So we can set owner to 1 for
reader-owned, -1 for writer-owned. The owner is unknown in both cases.

To handle transfer of rwsem ownership, the higher level code should
set the owner field to -1 to indicate a write-locked rwsem with unknown
owner.  Optimistic spinning will be disabled in this case.

Once the higher level code figures who the new owner is, it can then
set the owner field accordingly.

Tested-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Davidlohr Bueso <dave@stgolabs.net>
Cc: Jan Kara <jack@suse.cz>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Theodore Y. Ts'o <tytso@mit.edu>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-fsdevel@vger.kernel.org
Link: http://lkml.kernel.org/r/1526420991-21213-2-git-send-email-longman@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
 		2018-06-21 04:03:00 +09:00
Documentation dt-bindings: panel: lvds: Fix path to display timing bindings 2018-06-21 04:02:51 +09:00
arch ARM: davinci: board-dm646x-evm: set VPIF capture card name 2018-06-21 04:03:00 +09:00
block blk-mq: fix sysfs inflight counter 2018-06-21 04:02:49 +09:00
certs License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
crypto PKCS#7: fix direct verification of SignerInfo signature 2018-05-30 07:52:01 +02:00
drivers clk: imx6ull: use OSC clock during AXI rate change 2018-06-21 04:03:00 +09:00
firmware License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fs afs: Fix the non-encryption of calls 2018-06-21 04:02:59 +09:00
include mtd: Fix comparison in map_word_andequal() 2018-06-21 04:02:59 +09:00
init init: fix false positives in W+X checking 2018-06-21 04:02:57 +09:00
ipc ipc/shm: fix shmat() nil address after round-down when remapping 2018-05-30 07:51:49 +02:00
kernel locking/rwsem: Add a new RWSEM_ANONYMOUSLY_OWNED flag 2018-06-21 04:03:00 +09:00
lib lib/test_kmod.c: fix limit check on number of test devices created 2018-05-30 07:52:14 +02:00
mm mm: memcg: add __GFP_NOWARN in __memcg_schedule_kmem_cache_create() 2018-06-21 04:02:46 +09:00
net net sched actions: fix invalid pointer dereferencing if skbedit flags missing 2018-06-21 04:02:57 +09:00
samples samples/bpf: Partially fixes the bpf.o build 2018-04-26 11:02:12 +02:00
scripts kconfig: Avoid format overflow warning from GCC 8.1 2018-06-11 22:49:18 +02:00
security selinux: KASAN: slab-out-of-bounds in xattr_getsecurity 2018-06-05 11:41:56 +02:00
sound ASoC: msm8916-wcd-analog: use threaded context for mbhc events 2018-06-21 04:02:44 +09:00
tools x86/pkeys/selftests: Add a test for pkey 0 2018-06-21 04:02:59 +09:00
usr initramfs: fix initramfs rebuilds w/ compression after disabling 2017-11-03 07:39:19 -07:00
virt KVM: arm/arm64: vgic: fix possible spectre-v1 in vgic_mmio_read_apr() 2018-06-21 04:02:49 +09:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore Add hch to .get_maintainer.ignore 2015-08-21 14:30:10 -07:00
.gitattributes .gitattributes: set git diff driver for C source code files 2016-10-07 18:46:30 -07:00
.gitignore kbuild: rpm-pkg: keep spec file until make mrproper 2018-02-13 10:19:46 +01:00
.mailmap .mailmap: Add Maciej W. Rozycki's Imagination e-mail address 2017-11-10 12:16:15 -08:00
COPYING
…
CREDITS MAINTAINERS: update TPM driver infrastructure changes 2017-11-09 17:58:40 -08:00
Kbuild License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
Kconfig License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
MAINTAINERS dt-bindings: Document mti,mips-cpc binding 2018-03-15 10:54:35 +01:00
Makefile Linux 4.14.50 2018-06-16 09:45:18 +02:00
README README: add a new README file, pointing to the Documentation/ 2016-10-24 08:12:35 -02:00

README 

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

This file was moved to Documentation/admin-guide/README.rst

Please notice that there are several guides for kernel developers and users.
These guides can be rendered in a number of formats, like HTML and PDF.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.

There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.

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.