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Max Kellermann 478dbf1217
fs/pipe: use spinlock in pipe_read() only if there is a watch_queue
If there is no watch_queue, holding the pipe mutex is enough to
prevent concurrent writes, and we can avoid the spinlock.

O_NOTIFICATION_QUEUE is an exotic and rarely used feature, and of all
the pipes that exist at any given time, only very few actually have a
watch_queue, therefore it appears worthwile to optimize the common
case.

This patch does not optimize pipe_resize_ring() where the spinlocks
could be avoided as well; that does not seem like a worthwile
optimization because this function is not called often.

Related commits:

- commit 8df441294d ("pipe: Check for ring full inside of the
  spinlock in pipe_write()")
- commit b667b86734 ("pipe: Advance tail pointer inside of wait
  spinlock in pipe_read()")
- commit 189b0ddc24 ("pipe: Fix missing lock in pipe_resize_ring()")

Signed-off-by: Max Kellermann <max.kellermann@ionos.com>
Message-Id: <20230921075755.1378787-4-max.kellermann@ionos.com>
Reviewed-by: David Howells <dhowells@redhat.com>
Signed-off-by: Christian Brauner <brauner@kernel.org>
History 2023-10-19 11:02:48 +02:00
arch Fix preemption delays in the SGX code, remove unnecessarily UAPI-exported code, 2023-09-10 10:39:31 -07:00
block block: fix pin count management when merging same-page segments 2023-09-06 07:32:27 -06:00
certs certs: Reference revocation list for all keyrings 2023-08-17 20:12:41 +00:00
crypto This update includes the following changes: 2023-08-29 11:23:29 -07:00
Documentation drm ci for 6.6-rc1 2023-09-10 11:55:26 -07:00
drivers drm ci for 6.6-rc1 2023-09-10 11:55:26 -07:00
fs fs/pipe: use spinlock in pipe_read() only if there is a watch_queue 2023-10-19 11:02:48 +02:00
include fs/pipe: move check to pipe_has_watch_queue() 2023-10-19 11:02:47 +02:00
init init/mount: print pretty name of root device when panics 2023-10-19 11:02:46 +02:00
io_uring Revert "io_uring: fix IO hang in io_wq_put_and_exit from do_exit()" 2023-09-07 09:41:49 -06:00
ipc Add x86 shadow stack support 2023-08-31 12:20:12 -07:00
kernel fs: rename __mnt_{want,drop}_write*() helpers 2023-09-11 15:05:50 +02:00
lib iov_iter: Kunit tests for page extraction 2023-09-09 15:11:49 -07:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm LoongArch changes for v6.6 2023-09-08 12:16:52 -07:00
net Including fixes from netfilter and bpf. 2023-09-07 18:33:07 -07:00
rust Documentation work keeps chugging along; stuff for 6.6 includes: 2023-08-30 20:05:42 -07:00
samples VFIO updates for v6.6-rc1 2023-08-30 20:36:01 -07:00
scripts Fix preemption delays in the SGX code, remove unnecessarily UAPI-exported code, 2023-09-10 10:39:31 -07:00
security Landlock updates for v6.6-rc1 2023-09-08 12:06:51 -07:00
sound sound fixes for 6.6-rc1 2023-09-08 13:07:50 -07:00
tools perf tools changes for v6.6: 2023-09-09 20:06:17 -07:00
usr initramfs: Encode dependency on KBUILD_BUILD_TIMESTAMP 2023-06-06 17:54:49 +09:00
virt ARM: 2023-09-07 13:52:20 -07:00
.clang-format iommu: Add for_each_group_device() 2023-05-23 08:15:51 +02:00
.cocciconfig scripts: add Linux .cocciconfig for coccinelle 2016-07-22 12:13:39 +02:00
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: set diff driver for Rust source code files 2023-05-31 17:48:25 +02:00
.gitignore kbuild: rpm-pkg: rename binkernel.spec to kernel.spec 2023-07-25 00:59:33 +09:00
.mailmap for-linus-2023083101 2023-09-01 12:31:44 -07:00
.rustfmt.toml rust: add .rustfmt.toml 2022-09-28 09:02:20 +02:00
COPYING COPYING: state that all contributions really are covered by this file 2020-02-10 13:32:20 -08:00
CREDITS USB: Remove Wireless USB and UWB documentation 2023-08-09 14:17:32 +02:00
Kbuild Kbuild updates for v6.1 2022-10-10 12:00:45 -07:00
Kconfig kbuild: ensure full rebuild when the compiler is updated 2020-05-12 13:28:33 +09:00
MAINTAINERS drm ci for 6.6-rc1 2023-09-10 11:55:26 -07:00
Makefile Linux 6.6-rc1 2023-09-10 16:28:41 -07:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.