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Tom Parkin 07b8ca3792 net/l2tp: convert tunnel rwlock_t to rcu
Previously commit e02d494d2c ("l2tp: Convert rwlock to RCU") converted
most, but not all, rwlock instances in the l2tp subsystem to RCU.

The remaining rwlock protects the per-tunnel hashlist of sessions which
is used for session lookups in the UDP-encap data path.

Convert the remaining rwlock to rcu to improve performance of UDP-encap
tunnels.

Note that the tunnel and session, which both live on RCU-protected
lists, use slightly different approaches to incrementing their refcounts
in the various getter functions.

The tunnel has to use refcount_inc_not_zero because the tunnel shutdown
process involves dropping the refcount to zero prior to synchronizing
RCU readers (via. kfree_rcu).

By contrast, the session shutdown removes the session from the list(s)
it is on, synchronizes with readers, and then decrements the session
refcount.  Since the getter functions increment the session refcount
with the RCU read lock held we prevent getters seeing a zero session
refcount, and therefore don't need to use refcount_inc_not_zero.

Signed-off-by: Tom Parkin <tparkin@katalix.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2021-11-29 12:11:25 +00:00
Documentation Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2021-11-26 13:45:19 -08:00
LICENSES LICENSES/dual/CC-BY-4.0: Git rid of "smart quotes" 2021-07-15 06:31:24 -06:00
arch Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2021-11-26 13:45:19 -08:00
block block: fix parameter not described warning 2021-11-25 09:32:19 -07:00
certs certs: Add support for using elliptic curve keys for signing modules 2021-08-23 19:55:42 +03:00
crypto Update to zstd-1.4.10 2021-11-13 15:32:30 -08:00
drivers net: mvneta: Add TC traffic shaping offload 2021-11-29 12:05:52 +00:00
fs fuse fixes for 5.16-rc3 2021-11-26 12:01:31 -08:00
include af_unix: Replace the big lock with small locks. 2021-11-26 18:01:58 -08:00
init kbuild: Fix -Wimplicit-fallthrough=5 error for GCC 5.x and 6.x 2021-11-14 18:59:49 -08:00
ipc shm: extend forced shm destroy to support objects from several IPC nses 2021-11-20 10:35:54 -08:00
kernel Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2021-11-26 13:45:19 -08:00
lib parisc: Increase FRAME_WARN to 2048 bytes on parisc 2021-11-22 07:37:31 +01:00
mm Fixes for 5.16 folios: 2021-11-25 10:13:56 -08:00
net net/l2tp: convert tunnel rwlock_t to rcu 2021-11-29 12:11:25 +00:00
samples s390 updates for 5.16-rc2 2021-11-20 10:55:50 -08:00
scripts Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/hid/hid 2021-11-24 09:44:13 -08:00
security selinux: fix NULL-pointer dereference when hashtab allocation fails 2021-11-19 16:11:39 -05:00
sound xen: branch for v5.16-rc3 2021-11-26 09:54:13 -08:00
tools af_unix: Remove UNIX_ABSTRACT() macro and test sun_path[0] instead. 2021-11-26 18:01:56 -08:00
usr initramfs: Check timestamp to prevent broken cpio archive 2021-10-24 13:48:40 +09:00
virt Merge branch 'kvm-5.16-fixes' into kvm-master 2021-11-18 02:11:57 -05:00
.clang-format clang-format: Update with the latest for_each macro list 2021-05-12 23:32:39 +02:00
.cocciconfig
.get_maintainer.ignore Opt out of scripts/get_maintainer.pl 2019-05-16 10:53:40 -07:00
.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 MAINTAINERS: update email address of Christian Borntraeger 2021-11-18 17:50:54 +01:00
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 Networking fixes for 5.16-rc3, including fixes from netfilter. 2021-11-26 12:58:53 -08:00
Makefile drm fixes for 5.16-rc3 2021-11-25 18:21:20 -08:00
README Drop all 00-INDEX files from Documentation/ 2018-09-09 15:08:58 -06:00

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.