tcp: Add memory barrier to tcp_push()

[Salvatore]

Recently a patch has been accepted on the Linux Kernel regarding the TCP stack which fix an additional +40ms latency on ARM64 CPU architecture without impacting other CPU types.

More information can be find in here: https://<email address hidden>/

Would be possible to include the following patch as part of Linux image on the most recent and LTS maintained Ubuntu versions?

Patch:
```
---
 net/ipv4/tcp.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index ff6838ca2e58..7bce79beca2b 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -722,6 +722,7 @@ void tcp_push(struct sock *sk, int flags, int mss_now,
   if (!test_bit(TSQ_THROTTLED, &sk->sk_tsq_flags)) {
    NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPAUTOCORKING);
    set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags);
+ smp_mb__after_atomic();
   }
   /* It is possible TX completion already happened
    * before we set TSQ_THROTTLED.
--
```

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the linux-aws/5.4.0-1122.132 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-focal-linux-aws' to 'verification-done-focal-linux-aws'. If the problem still exists, change the tag 'verification-needed-focal-linux-aws' to 'verification-failed-focal-linux-aws'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the linux-aws/6.5.0-1017.17 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-mantic-linux-aws' to 'verification-done-mantic-linux-aws'. If the problem still exists, change the tag 'verification-needed-mantic-linux-aws' to 'verification-failed-mantic-linux-aws'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the linux-aws-fips/5.15.0-1057.63+fips1 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-jammy-linux-aws-fips' to 'verification-done-jammy-linux-aws-fips'. If the problem still exists, change the tag 'verification-needed-jammy-linux-aws-fips' to 'verification-failed-jammy-linux-aws-fips'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Ubuntu Kernel Bot (ubuntu-kernel-bot)]

This bug is awaiting verification that the linux-aws-5.15/5.15.0-1057.63~20.04.1 kernel in -proposed solves the problem. Please test the kernel and update this bug with the results. If the problem is solved, change the tag 'verification-needed-focal-linux-aws-5.15' to 'verification-done-focal-linux-aws-5.15'. If the problem still exists, change the tag 'verification-needed-focal-linux-aws-5.15' to 'verification-failed-focal-linux-aws-5.15'.

If verification is not done by 5 working days from today, this fix will be dropped from the source code, and this bug will be closed.

See https://wiki.ubuntu.com/Testing/EnableProposed for documentation how to enable and use -proposed. Thank you!

[Roxana Nicolescu (roxanan)]

This was added to linux-aws, not linux and it messed up the verification process

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-aws - 5.4.0-1122.132

---------------
linux-aws (5.4.0-1122.132) focal; urgency=medium

  * focal/linux-aws: 5.4.0-1122.132 -proposed tracker (LP: #2055639)

  * Focal update: v5.4.267 upstream stable release (LP: #2054406)
    - [Config] Update annotations for CONFIG_SND_MESON_CODEC_GLUE

  * Packaging resync (LP: #1786013)
    - [Packaging] drop ABI data
    - debian.aws/dkms-versions -- update from kernel-versions (main/2024.03.04)

  * aws: Backport latest ENA driver in upstream Linux to enable IRQ moderation
    (LP: #2056475)
    - net: ena: Enable DIM by default

  * tcp: Add memory barrier to tcp_push() (LP: #2051727)
    - tcp: Add memory barrier to tcp_push()

  [ Ubuntu: 5.4.0-175.195 ]

  * focal/linux: 5.4.0-175.195 -proposed tracker (LP: #2055684)
  * Packaging resync (LP: #1786013)
    - [Packaging] drop ABI data
    - [Packaging] update annotations scripts
    - debian.master/dkms-versions -- update from kernel-versions (main/2024.03.04)
  * Drop ABI checks from kernel build (LP: #2055686)
    - [Packaging] Remove in-tree abi checks
    - [Packaging] Bring back install-<flavour> prerequisite for checks-<flavour>
    - [Packaging] Remove abi-check from final-checks
  * Cranky update-dkms-versions rollout (LP: #2055685)
    - [Packaging] remove update-dkms-versions
    - Move debian/dkms-versions to debian.master/dkms-versions
    - [Packaging] Replace debian/dkms-versions with $(DEBIAN)/dkms-versions
    - [Packaging] remove update-version-dkms
  * linux-tools-common: man page of usbip[d] is misplaced (LP: #2054094)
    - [Packaging] rules: Put usbip manpages in the correct directory
  * CVE-2024-23851
    - dm ioctl: log an error if the ioctl structure is corrupted
    - dm: limit the number of targets and parameter size area
  * Focal update: v5.4.268 upstream stable release (LP: #2055075)
    - f2fs: explicitly null-terminate the xattr list
    - pinctrl: lochnagar: Don't build on MIPS
    - ALSA: hda - Fix speaker and headset mic pin config for CHUWI CoreBook XPro
    - ASoC: Intel: Skylake: Fix mem leak in few functions
    - ASoC: nau8822: Fix incorrect type in assignment and cast to restricted
      __be16
    - ASoC: Intel: Skylake: mem leak in skl register function
    - ASoC: cs43130: Fix the position of const qualifier
    - ASoC: cs43130: Fix incorrect frame delay configuration
    - ASoC: rt5650: add mutex to avoid the jack detection failure
    - nouveau/tu102: flush all pdbs on vmm flush
    - net/tg3: fix race condition in tg3_reset_task()
    - ASoC: da7219: Support low DC impedance headset
    - nvme: introduce helper function to get ctrl state
    - drm/exynos: fix a potential error pointer dereference
    - drm/exynos: fix a wrong error checking
    - clk: rockchip: rk3128: Fix HCLK_OTG gate register
    - jbd2: correct the printing of write_flags in jbd2_write_superblock()
    - drm/crtc: Fix uninit-value bug in drm_mode_setcrtc
    - neighbour: Don't let neigh_forced_gc() disable preemption for long
    - tracing: Have large events show up as '[LINE TOO BIG]' instead of nothing
    - tracing: Add size check when printing trace_marker output
    - ring-buffer: Do not ...

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-aws - 6.5.0-1017.17

---------------
linux-aws (6.5.0-1017.17) mantic; urgency=medium

  * mantic/linux-aws: 6.5.0-1017.17 -proposed tracker (LP: #2055564)

  * Packaging resync (LP: #1786013)
    - [Packaging] drop ABI data
    - debian.aws/dkms-versions -- update from kernel-versions (main/2024.03.04)

  * linux: please move dmi-sysfs.ko (CONFIG_DMI_SYSFS for SMBIOS support) from
    linux-modules-extra to linux-modules (LP: #2045561)
    - [Packaging] Move dmi-sysfs.ko into linux-modules

  * linux: please move erofs.ko (CONFIG_EROFS for EROFS support) from linux-
    modules-extra to linux-modules (LP: #2054809)
    - UBUNTU [Packaging]: Include erofs in linux-modules instead of linux-modules-
      extra

  * aws: Backport latest ENA driver in upstream Linux to enable IRQ moderation
    (LP: #2056475)
    - net: ena: Enable DIM by default

  * tcp: Add memory barrier to tcp_push() (LP: #2051727)
    - tcp: Add memory barrier to tcp_push()

  [ Ubuntu: 6.5.0-27.28 ]

  * mantic/linux: 6.5.0-27.28 -proposed tracker (LP: #2055584)
  * Packaging resync (LP: #1786013)
    - [Packaging] drop ABI data
    - [Packaging] update annotations scripts
    - debian.master/dkms-versions -- update from kernel-versions (main/2024.03.04)
  * CVE-2024-26597
    - net: qualcomm: rmnet: fix global oob in rmnet_policy
  * CVE-2024-26599
    - pwm: Fix out-of-bounds access in of_pwm_single_xlate()
  * Drop ABI checks from kernel build (LP: #2055686)
    - [Packaging] Remove in-tree abi checks
  * Cranky update-dkms-versions rollout (LP: #2055685)
    - [Packaging] remove update-dkms-versions
    - Move debian/dkms-versions to debian.master/dkms-versions
    - [Packaging] Replace debian/dkms-versions with $(DEBIAN)/dkms-versions
  * linux: please move erofs.ko (CONFIG_EROFS for EROFS support) from linux-
    modules-extra to linux-modules (LP: #2054809)
    - UBUNTU [Packaging]: Include erofs in linux-modules instead of linux-modules-
      extra
  * performance: Scheduler: ratelimit updating of load_avg (LP: #2053251)
    - sched/fair: Ratelimit update to tg->load_avg
  * IB peer memory feature regressed in 6.5 (LP: #2055082)
    - SAUCE: RDMA/core: Introduce peer memory interface
  * linux-tools-common: man page of usbip[d] is misplaced (LP: #2054094)
    - [Packaging] rules: Put usbip manpages in the correct directory
  * CVE-2024-23851
    - dm: limit the number of targets and parameter size area
  * CVE-2024-23850
    - btrfs: do not ASSERT() if the newly created subvolume already got read
  * x86: performance: tsc: Extend watchdog check exemption to 4-Sockets platform
    (LP: #2054699)
    - x86/tsc: Extend watchdog check exemption to 4-Sockets platform
  * linux: please move dmi-sysfs.ko (CONFIG_DMI_SYSFS for SMBIOS support) from
    linux-modules-extra to linux-modules (LP: #2045561)
    - [Packaging] Move dmi-sysfs.ko into linux-modules
  * Fix AMD brightness issue on AUO panel (LP: #2054773)
    - drm/amdgpu: make damage clips support configurable
  * Mantic update: upstream stable patchset 2024-02-28 (LP: #2055199)
    - f2fs: explicitly null-terminate the xattr list
    - pinctrl: lochnagar: Don't build on MI...

[Launchpad Janitor (janitor)]

This bug was fixed in the package linux-aws - 5.15.0-1057.63

---------------
linux-aws (5.15.0-1057.63) jammy; urgency=medium

  * Packaging resync (LP: #1786013)
    - debian.aws/dkms-versions -- update from kernel-versions (main/2024.03.04)

 -- Philip Cox <email address hidden> Tue, 19 Mar 2024 12:10:59 -0400