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Kui-Feng Lee b671c2067a bpf: Retire the struct_ops map kvalue->refcnt.
We have replaced kvalue-refcnt with synchronize_rcu() to wait for an
RCU grace period.

Maintenance of kvalue->refcnt was a complicated task, as we had to
simultaneously keep track of two reference counts: one for the
reference count of bpf_map. When the kvalue->refcnt reaches zero, we
also have to reduce the reference count on bpf_map - yet these steps
are not performed in an atomic manner and require us to be vigilant
when managing them. By eliminating kvalue->refcnt, we can make our
maintenance more straightforward as the refcount of bpf_map is now
solely managed!

To prevent the trampoline image of a struct_ops from being released
while it is still in use, we wait for an RCU grace period. The
setsockopt(TCP_CONGESTION, "...") command allows you to change your
socket's congestion control algorithm and can result in releasing the
old struct_ops implementation. It is fine. However, this function is
exposed through bpf_setsockopt(), it may be accessed by BPF programs
as well. To ensure that the trampoline image belonging to struct_op
can be safely called while its method is in use, the trampoline
safeguarde the BPF program with rcu_read_lock(). Doing so prevents any
destruction of the associated images before returning from a
trampoline and requires us to wait for an RCU grace period.

Signed-off-by: Kui-Feng Lee <kuifeng@meta.com>
Link: https://lore.kernel.org/r/20230323032405.3735486-2-kuifeng@meta.com
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
2023-03-22 22:51:47 -07:00
arch bpf-next-for-netdev 2023-03-06 20:36:39 -08:00
block Driver core changes for 6.3-rc1 2023-02-24 12:58:55 -08:00
certs Kbuild updates for v6.3 2023-02-26 11:53:25 -08:00
crypto Networking changes for 6.3. 2023-02-21 18:24:12 -08:00
Documentation bpf, docs: Libbpf overview documentation 2023-03-18 10:17:39 -07:00
drivers net: microchip: sparx5: Add TC template support 2023-03-08 13:19:43 +00:00
fs ARM: SoC drivers for 6.3 2023-02-27 10:04:49 -08:00
include bpf: Retire the struct_ops map kvalue->refcnt. 2023-03-22 22:51:47 -07:00
init Kbuild updates for v6.3 2023-02-26 11:53:25 -08:00
io_uring net: reclaim skb->scm_io_uring bit 2023-03-08 13:21:47 +00:00
ipc Merge branch 'work.namespace' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs 2023-02-24 19:20:07 -08:00
kernel bpf: Retire the struct_ops map kvalue->refcnt. 2023-03-22 22:51:47 -07:00
lib Kernel concurrency sanitizer (KCSAN) updates for v6.3 2023-02-25 13:02:20 -08:00
LICENSES LICENSES: Add the copyleft-next-0.3.1 license 2022-11-08 15:44:01 +01:00
mm memblock: small optimizations 2023-02-27 09:34:53 -08:00
net bpf: return long from bpf_map_ops funcs 2023-03-22 15:11:30 -07:00
rust Kbuild updates for v6.3 2023-02-26 11:53:25 -08:00
samples bpf: use canonical ftrace path 2023-03-13 21:51:30 -07:00
scripts Kbuild updates for v6.3 2023-02-26 11:53:25 -08:00
security powerpc updates for 6.3 2023-02-25 11:00:06 -08:00
sound ARM: SoC drivers for 6.3 2023-02-27 10:04:49 -08:00
tools selftests/bpf: Check when bounds are not in the 32-bit range 2023-03-22 16:49:25 -07:00
usr usr/gen_init_cpio.c: remove unnecessary -1 values from int file 2022-10-03 14:21:44 -07:00
virt KVM/riscv changes for 6.3 2023-02-15 12:33:28 -05:00
.clang-format media: subdev: Add for_each_active_route() macro 2023-01-22 09:35:57 +01:00
.cocciconfig
.get_maintainer.ignore get_maintainer: add Alan to .get_maintainer.ignore 2022-08-20 15:17:44 -07:00
.gitattributes .gitattributes: use 'dts' diff driver for *.dtso files 2023-02-26 15:28:23 +09:00
.gitignore .gitignore: ignore *.cover and *.mbx 2023-02-05 18:51:22 +09:00
.mailmap 12 hotfixes, mostly against mm/. Five of these fixes are cc:stable. 2023-02-13 14:09:20 -08:00
.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 There is no particular theme here - mainly quick hits all over the tree. 2023-02-23 17:55:40 -08:00
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 ARM: SoC fixes for 6.3, part 1 2023-02-27 10:09:40 -08:00
Makefile Kbuild updates for v6.3 2023-02-26 11:53:25 -08:00
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.