Pull networking updates from Jakub Kicinski:
 "One of the 'small improvements all over the place' releases for us.

  It's hard to draw any direct comparisons because summer vacations
  disrupted our patch processing (and presumably - generation) quite a
  bit.

  Quick and dirty count suggests we (Paolo and I) merged a very similar
  number of net (632) and net-next (648) patches. This is not telling
  the full story either because 1/3 to 1/2 of the net-next patches also
  *seem* like AI-driven low priority fixes, cleanups and clarifications.

  We are completely overwhelmed, of course. The glimmer of hope is that
  we secured sufficient LLM budget and access (thank you Meta!) to run
  reviews with multiple frontier models on each patch. This eliminates
  some hallucinations. That said, in terms of review, the LLMs can only
  do so much.

  The sad truth is that our APIs (especially for rare events like PCIe
  errors, timeouts etc) have always been racy, and now LLMs don't let us
  ignore that. I expect our direction for the next release will be to
  tweak the reviews a little bit more, but start shifting focus to
  letting the LLMs take care of the busy work - managing patchwork,
  automating common process complaints, editing commit messages, and
  maybe applying patches which already got "reviewed-by" tags from
  people we trust...

  Core & protocols:

   - A few steps lowering rtnl_lock dependence:
      - per-netns netdev unregistration for select SW drivers (e.g.
        veth, ipvlan, tunnels)
      - rtnl_lock-less FIB rule changes (RTM_NEWRULE and RTM_DELRULE)
      - prepare software drivers and TC qdiscs for rtnl_lock-less GET

   - Support BIG TCP (>64kB TSO) in UDP tunnels (vxlan, geneve)

   - Support buffers larger than PAGE_SIZE in devmem zero-copy API

   - Improve MPTCP handling of extreme memory pressure handling, when
     out-of-order queue had to be pruned

   - Report the per-group user count via RTM_GETMULTICAST

   - Expose the route deletion reason in RTM_DELROUTE

   - Add a SO_RIGHTS_NOTRUNC option to UNIX sockets to enable more
     useful handling of LSM denials when receiving SCM_RIGHTS messages:
     instead of truncating the message at the first blocked fd, keep
     every fd slot and store the LSM errno in the blocked slot

   - IPv6 Segment Routing - support looking up the post-encap SID
     (address) in a different/specified routing table

   - Support PRP RedBox (interlink) creation

   - Support per-nexthop UDP dst port in VXLAN

   - Continue converting getsockopt callbacks in a number of protocols
     to iov_iter

  Ethernet:

   - Merge initial CXL support for AMD/Solarflare NICs (shared branch
     with the CXL tree)

   - New drivers:
      - ADIN1140 10BASE-T1S MACPHY
      - Initial skeleton of Intel iXD and ZTE Dinghai drivers

   - High-speed NICs:
      - AMD/Pensando:
         - support firmware flashing
      - Cisco (enic):
         - SR-IOV V2 admin channel and MBOX protocol
      - Huawei (hns3):
         - support for ethtool pfc_prevention_tout
      - nVidia/Mellanox:
         - support sharing bandwidth control across interfaces
           of the same device
      - Marvell (octeontx2-pf):
         - link RQ page pools to netdev for Netlink stats
      - Google vNIC:
         - XDP metadata support for DQ RDA
      - Microsoft vNIC:
         - support forcing full-page RX buffers

   - Other NICs:
      - Synopsys IP:
         - eic7700: support for eth1
      - Microchip (lan743x):
         - support for RMII interface
      - Wangxun:
         - support for ethtool -G and -C for VFs
         - add Tx timeout and PCIe error handling
      - Intel (igb/igc):
         - RSS key get/set support
         - support for forcing link speed without auto-negotiation

   - Switches:
      - NXP (dpaa2):
         - support bonding/LAG offload
      - Mediatek:
         - mt7530: EN7528 support
         - initial support for MT7628
      - Micrel (ksz8/9):
         - refactoring work to move towards library model
         - PTP support for KSZ8463
      - nVidia/Mellanox:
         - support rtnl-lock-less ethtool callbacks
      - Realtek:
         - rtl8366rb: use generic RTL83xx code
         - support SGMII and HSGMII for RTL8367S

   - PHYs:
      - Airoha:
         - EcoNet EN7528 PHY support
      - DAPU Telecom
         - DAPU Telecom DAP8211R(I) Gigabit PHY support
      - Realtek:
         - support RTL8261C_CG
         - support RTL8261D

  Wireless:

   - nl80211: per-link statistics support for multi-link operation

   - mac80211: AQL/airtime-fairness support for multicast

   - Merge Peripheral Authentication Service (PAS) / TEE support for
     ath12k (shared branch with the firmware/qcom tree)

   - New drivers:
      - mm81x for Morse Micro Long-Range S1G devices
      - nxpwifi for NXP devices (mostly forked off from mwifiex)

   - Driver changes:
      - Broadcom (brcmfmac):
         - DPP support, some Cypress part update
      - MediaTek (mt76):
         - mt7928 support
         - mt7925 NAN support
         - mt7996 AP powersave improvements
      - Qualcomm (ath12k):
         - much kernel infrastructure integration work
         - AHB platform MultiPD support
      - Realtek (rt89):
         - LED support
         - RTL8922DE support
         - dual-BT coex for RTL8922D
      - Intel:
         - new FW version support

  Bluetooth:

   - HCI: add support for Shorter Connection Interval (SCI) feature

   - af_bluetooth: add minimal context analysis annotations

   - Driver changes:
      - Intel:
         - add Bluetooth SAR revision 2 support
         - add vendor_reset PCI sysfs for PLDR
      - Mediatek:
         - add USB IDs for MT7902 and MT7922 devices
      - Realtek:
         - add USB IDs for 8761CU and 8852BE devices
      - NXP:
         - add M.2 Bluetooth device support using pwrseq

  Misc:

   - DPLL support for manual/numerical oscillator control (NCO)
     (implement in zl3073x)

   - MCTP support for MCTP over USB v1.1 (DMTF DSP0283)

   - Power-over-Ethernet: support Realtek PSE controllers

   - Remove the IBM EHEA driver

   - Remove tulip/xircom_cb driver"

* tag 'net-next-7.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1433 commits)
  net/mlx5e: do not HW-GRO coalesce small frames
  net: openvswitch: fix nf_connlabels leak in ovs_ct_init
  net: add missing ref_tracker_dir_exit() to alloc_netdev_mqs()
  net: openvswitch: fix flow mask use-after-free on flow deletion
  sctp: stop processing a packet once its association is deleted
  dpll: zl3073x: add PTP clock support
  dpll: zl3073x: add channel ToD, phase step and TIE operations
  dpll: zl3073x: scale poll interval proportionally to timeout
  ptp: vmclock: prevent read-only mappings from becoming writable
  ipv4: reject undersized MTUs in ip_do_fragment()
  bonding: initialize err for empty target lists
  net: dsa: initial support for MT7628 embedded switch
  net: dsa: initial MT7628 tagging driver
  net: phy: mediatek: add phy driver for MT7628 built-in Fast Ethernet PHYs
  dt-bindings: net: dsa: add MT7628 ESW
  net: pse-pd: realtek-pse-mcu: add UART transport
  net: pse-pd: realtek-pse-mcu: add I2C transport
  net: pse-pd: add Realtek PSE MCU core
  dt-bindings: net: pse-pd: add bindings for Realtek PSE MCU
  vsock: use sock_error() to consume sk_err after a failed connect
  ...

Right now if some LSM such as Smack denies an AF_UNIX socket peer to
receive an SCM_RIGHTS fd, the SCM_RIGHTS fd array will be cut short at
that point, and MSG_CTRUNC is set on return of recvmsg(). This is
highly problematic behaviour, because it leaves the receiver
wondering what happened. As per man page MSG_CTRUNC is supposed to
indicate that the control buffer was sized too short, but suddenly
a permission error might result in the exact same flag being set.
Moreover, the receiver has no chance to determine how many fds got
originally sent and how many were suppressed.[1]

Add a SO_RIGHTS_NOTRUNC option to UNIX sockets to enable more useful
handling of LSM denials when receiving SCM_RIGHTS messages: instead of
truncating the message at the first blocked fd, keep every fd slot
and store the LSM errno in the blocked slot. The socket option is
inherited by the child accept() socket if set on the listen() socket.

[1]: https://github.com/uapi-group/kernel-features#useful-handling-of-lsm-denials-on-scm_rights

Reviewed-by: Christian Brauner (Amutable) <brauner@kernel.org>
Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl>
Link: https://patch.msgid.link/20260813162818.149248-4-jkoolstra@xs4all.nl
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Wire up the fchroot() system call as number 472 on (nearly) all
architectures and sync the mirrored copies of the syscall tables and
the asm-generic unistd.h under tools/.

Link: https://patch.msgid.link/20260724-work-failfs-v2-5-485dabbae185@kernel.org
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

Pull misc vfs updates from Christian Brauner:
 "Features:

   - Reduce pipe->mutex contention by pre-allocating pages outside the
     lock in anon_pipe_write().

     anon_pipe_write() called alloc_page() once per page while holding
     pipe->mutex. The allocation can sleep doing direct reclaim and runs
     memcg charging, which extends the critical section and stalls any
     concurrent reader on the same mutex. Now up to 8 pages are
     pre-allocated before the mutex is taken, leftovers are recycled
     into the per-pipe tmp_page[] cache before unlock, and any remainder
     is released after unlock, keeping the allocator out of the critical
     section on both sides. On a writers x readers sweep with 64KB
     writes against a 1 MB pipe throughput improves 6-28% and average
     write latency drops 5-22%; under memory pressure - when the cost of
     holding the mutex across reclaim is highest - throughput improves
     21-48% and latency drops 17-33%. The microbenchmark is added to
     selftests.

   - uaccess/sockptr: fix the ignored_trailing logic in
     copy_struct_to_user() to behave as documented and the usize check
     in copy_struct_from_sockptr() for user pointers, and add
     copy_struct_{from,to}_bounce_buffer() and copy_struct_to_sockptr()
     helpers for upcoming users (IPPROTO_SMBDIRECT, IPPROTO_QUIC).

   - bpf: add a sleepable bpf_real_inode() kfunc that resolves the real
     inode backing a dentry via d_real_inode(). On overlayfs the inode
     attached to the dentry doesn't carry the underlying device
     information; this is used by the filesystem restriction BPF program
     that was merged into systemd.

   - docs: add guidelines for submitting new filesystems, motivated by
     the maintenance burden abandoned and untestable filesystems impose
     on VFS developers, blocking infrastructure work like folio
     conversions and iomap migration.

  Fixes:

   - libfs: set SB_I_NOEXEC and SB_I_NODEV by default in init_pseudo()
     and drop the now-redundant assignments in callers. This began as a
     one-line dma-buf fix for a path_noexec() warning; a pseudo
     filesystem has no reason not to set SB_I_NOEXEC. All init_pseudo()
     callers were audited: the only visible effect is on dma-buf where
     SB_I_NOEXEC silences the warning.

   - Handle set_blocksize() failures in legacy filesystems (bfs, hpfs,
     qnx4, jfs, befs, affs, isofs, minix, ntfs3, omfs). Mounting a
     device with a sector size > PAGE_SIZE crashed roughly half of them;
     the rest had the same missing error handling pattern. Plus a
     follow-up releasing the superblock buffer_head when setting the
     minix v3 block size fails.

   - mount: honour SB_NOUSER in the new mount API.

   - fs/fcntl: fix a SOFTIRQ-unsafe lock order in fasync signaling by
     switching the process-group paths of send_sigio() and send_sigurg()
     from read_lock(&tasklist_lock) to RCU, matching the single-PID
     path.

   - vfs: add an FS_USERNS_DELEGATABLE flag and set it for NFS, fixing
     delegated NFS mounts (fsopen() in a container with the mount
     performed by a privileged daemon) that broke when non-init
     s_user_ns was tied to FS_USERNS_MOUNT.

   - selftests/namespaces: fix a hang in nsid_test where an unreaped
     grandchild kept the TAP pipe write-end open, a waitpid(-1) race in
     listns_efault_test, and a false FAIL on kernels without listns()
     where the tests should SKIP.

   - filelock: fix the break_lease() stub signature for
     CONFIG_FILE_LOCKING=n.

   - init/initramfs_test: wait for the async initramfs unpacking before
     running; the test and do_populate_rootfs() share the parser state.

   - fs/coredump: reduce redundant log noise in
     validate_coredump_safety().

   - iomap: pass the correct length to fserror_report_io() in
     __iomap_write_begin().

   - backing-file: fix the backing_file_open() kerneldoc.

  Cleanups:

   - initramfs: refactor the cpio hex header parsing to use hex2bin()
     instead of the hand-rolled simple_strntoul() which is reverted, and
     extend the initramfs KUnit tests to cover header fields with 0x
     prefixes.

   - Replace __get_free_pages() and friends with kmalloc()/kzalloc()
     across quota, proc, ocfs2/dlm, nilfs2, nfs, nfsd, libfs, jfs, jbd2,
     isofs, fuse, select, namespace, configfs, binfmt_misc, bfs, and the
     do_mounts init code - part of the larger work of replacing page
     allocator calls with kmalloc().

   - Use clear_and_wake_up_bit() in unlock_buffer() and
     journal_end_buffer_io_sync() instead of open-coding the sequence.

   - Drop unused VFS exports: unexport drop_super_exclusive(), remove
     start_removing_user_path_at(), and fold __start_removing_path()
     into start_removing_path().

   - fs/read_write: narrow the __kernel_write() export with
     EXPORT_SYMBOL_FOR_MODULES().

   - vfs: uapi: retire octal and hex constants in favor of (1 << n) for
     the O_ flags. Finding a free bit for a new flag across the
     architectures was needlessly hard with the mixed bases.

   - dcache: add extra sanity checks of dead dentries in dentry_free()
     via a new DENTRY_WARN_ONCE() that also prints d_flags.

   - iov_iter: use kmemdup_array() in dup_iter() to harden the
     allocation against multiplication overflow.

   - fs/pipe: write to ->poll_usage only once.

   - vfs: remove an always-taken if-branch in find_next_fd().

   - dcache: use kmalloc_flex() for struct external_name in __d_alloc().

   - namei: use QSTR() instead of QSTR_INIT() in path_pts().

   - sync_file_range: delete dead S_ISLNK code.

   - Comment fixes: retire a stale comment in fget_task_next() and fix
     assorted spelling mistakes"

* tag 'vfs-7.2-rc1.misc' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: (73 commits)
  backing-file: fix backing_file_open() kerneldoc parameter
  iomap: pass the correct len to fserror_report_io in __iomap_write_begin
  vfs: add FS_USERNS_DELEGATABLE flag and set it for NFS
  filelock: fix break_lease() stub signature for CONFIG_FILE_LOCKING=n
  vfs: uapi: retire octal and hex numbers in favor of (1 << n) for O_ flags
  bpf: add bpf_real_inode() kfunc
  fs/read_write: Do not export __kernel_write() to the entire world
  libfs: drop redundant SB_I_NOEXEC/SB_I_NODEV in init_pseudo() callers
  libfs: set SB_I_NOEXEC and SB_I_NODEV by default in init_pseudo()
  mount: honour SB_NOUSER in the new mount API
  fs/fcntl: fix SOFTIRQ-unsafe lock order in fasync signaling
  selftests/pipe: add pipe_bench microbenchmark
  fs/pipe: pre-allocate pages outside pipe->mutex in anon_pipe_write
  fs: retire stale comment in fget_task_next()
  fs: fix spelling mistakes in comment
  bfs: replace get_zeroed_page() with kzalloc()
  binfmt_misc: replace __get_free_page() with kmalloc()
  configfs: replace __get_free_pages() with kzalloc()
  fs/namespace: use __getname() to allocate mntpath buffer
  fs/select: replace __get_free_page() with kmalloc()
  ...

A recent build failure[1] exposed the diffculty of working with the
current octal and hex definitions of O_ flags when trying to find a gap
for a new flag. This difficulty is compounded by the fact that O_ flags
may have architectural specific values.

Replace the hex/octal #defines, which are hard to parse when looking for
free bits, with explicit bit shifts like (1 << 11). Also, add comments
that identify which architectures redefine some of the seemingly free
("cursed") bits in uapi/asm-generic/fcntl.h. These should not be used to
define new O_ flags (for now, at least).

The translastion was done with Claude Opus 4.8, and verified with a
(non-AI) gawk script. The accounting of which architectures claim
which bit-gaps in uapi/asm-generic/fcntl.h is also done by hand.

[1]: https://lore.kernel.org/all/agruPPybCx8q2XcJ@sirena.org.uk/

Assisted-by: Claude:Opus 4.8
Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl>
Link: https://patch.msgid.link/20260604222405.5382-1-jkoolstra@xs4all.nl
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

Introduce a new error code EFTYPE for wrong file type operations.
EFTYPE is already used in BSD systems like FreeBSD and macOS.

This will be used by the upcoming OPENAT2_REGULAR flag support to
return a specific error when a path doesn't refer to a regular file.

Signed-off-by: Dorjoy Chowdhury <dorjoychy111@gmail.com>
Link: https://patch.msgid.link/20260328172314.45807-2-dorjoychy111@gmail.com
Reviewed-by: Jeff Layton <jlayton@kernel.org>
Reviewed-by: Aleksa Sarai <aleksa@amutable.com>
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

To get an operable version of an O_PATH file descriptor, it is possible
to use openat(fd, ".", O_DIRECTORY) for directories, but other files
currently require going through open("/proc/<pid>/fd/<nr>"), which
depends on a functioning procfs.

This patch adds the O_EMPTYPATH flag to openat(2)/openat2(2). If passed,
LOOKUP_EMPTY is set at path resolution time.

Note: This implies that you cannot rely anymore on disabling procfs from
being mounted (e.g. inside a container without procfs mounted and with
CAP_SYS_ADMIN dropped) to prevent O_PATH fds from being re-opened
read-write.

Signed-off-by: Jori Koolstra <jkoolstra@xs4all.nl>
Link: https://patch.msgid.link/20260424114611.1678641-2-jkoolstra@xs4all.nl
Signed-off-by: Christian Brauner (Amutable) <brauner@kernel.org>

Pull scheduler updates from Ingo Molnar:
 "Scheduler Kconfig space updates:

   - Further consolidate configurable preemption modes (Peter Zijlstra)

     Reduce the number of architectures that are allowed to offer
     PREEMPT_NONE and PREEMPT_VOLUNTARY, reducing the number of
     preemption models from four to just two: 'full' and 'lazy' on
     up-to-date architectures (arm64, loongarch, powerpc, riscv, s390,
     x86).

     None and voluntary are only available as legacy features on
     platforms that don't implement lazy preemption yet, or which don't
     even support preemption.

     The goal is to eventually remove cond_resched() and voluntary
     preemption altogether.

  RSEQ based 'scheduler time slice extension' support (Thomas Gleixner
  and Peter Zijlstra):

  This allows a thread to request a time slice extension when it enters
  a critical section to avoid contention on a resource when the thread
  is scheduled out inside of the critical section.

   - Add fields and constants for time slice extension
   - Provide static branch for time slice extensions
   - Add statistics for time slice extensions
   - Add prctl() to enable time slice extensions
   - Implement sys_rseq_slice_yield()
   - Implement syscall entry work for time slice extensions
   - Implement time slice extension enforcement timer
   - Reset slice extension when scheduled
   - Implement rseq_grant_slice_extension()
   - entry: Hook up rseq time slice extension
   - selftests: Implement time slice extension test
   - Allow registering RSEQ with slice extension
   - Move slice_ext_nsec to debugfs
   - Lower default slice extension
   - selftests/rseq: Add rseq slice histogram script

  Scheduler performance/scalability improvements:

   - Update rq->avg_idle when a task is moved to an idle CPU, which
     improves the scalability of various workloads (Shubhang Kaushik)

   - Reorder fields in 'struct rq' for better caching (Blake Jones)

   - Fair scheduler SMP NOHZ balancing code speedups (Shrikanth Hegde):
      - Move checking for nohz cpus after time check
      - Change likelyhood of nohz.nr_cpus
      - Remove nohz.nr_cpus and use weight of cpumask instead

   - Avoid false sharing for sched_clock_irqtime (Wangyang Guo)

   - Cleanups (Yury Norov):
      - Drop useless cpumask_empty() in find_energy_efficient_cpu()
      - Simplify task_numa_find_cpu()
      - Use cpumask_weight_and() in sched_balance_find_dst_group()

  DL scheduler updates:

   - Add a deadline server for sched_ext tasks (by Andrea Righi and Joel
     Fernandes, with fixes by Peter Zijlstra)

  RT scheduler updates:

   - Skip currently executing CPU in rto_next_cpu() (Chen Jinghuang)

  Entry code updates and performance improvements (Jinjie Ruan)

  This is part of the scheduler tree in this cycle due to inter-
  dependencies with the RSEQ based time slice extension work:

    - Remove unused syscall argument from syscall_trace_enter()
    - Rework syscall_exit_to_user_mode_work() for architecture reuse
    - Add arch_ptrace_report_syscall_entry/exit()
    - Inline syscall_exit_work() and syscall_trace_enter()

  Scheduler core updates (Peter Zijlstra):

   - Rework sched_class::wakeup_preempt() and rq_modified_*()
   - Avoid rq->lock bouncing in sched_balance_newidle()
   - Rename rcu_dereference_check_sched_domain() =>
            rcu_dereference_sched_domain()
   - <linux/compiler_types.h>: Add the __signed_scalar_typeof() helper

  Fair scheduler updates/refactoring (Peter Zijlstra and Ingo Molnar):

   - Fold the sched_avg update
   - Change rcu_dereference_check_sched_domain() to rcu-sched
   - Switch to rcu_dereference_all()
   - Remove superfluous rcu_read_lock()
   - Limit hrtick work
   - Join two #ifdef CONFIG_FAIR_GROUP_SCHED blocks
   - Clean up comments in 'struct cfs_rq'
   - Separate se->vlag from se->vprot
   - Rename cfs_rq::avg_load to cfs_rq::sum_weight
   - Rename cfs_rq::avg_vruntime to ::sum_w_vruntime & helper functions
   - Introduce and use the vruntime_cmp() and vruntime_op() wrappers for
     wrapped-signed aritmetics
   - Sort out 'blocked_load*' namespace noise

  Scheduler debugging code updates:

   - Export hidden tracepoints to modules (Gabriele Monaco)

   - Convert copy_from_user() + kstrtouint() to kstrtouint_from_user()
     (Fushuai Wang)

   - Add assertions to QUEUE_CLASS (Peter Zijlstra)

   - hrtimer: Fix tracing oddity (Thomas Gleixner)

  Misc fixes and cleanups:

   - Re-evaluate scheduling when migrating queued tasks out of throttled
     cgroups (Zicheng Qu)

   - Remove task_struct->faults_disabled_mapping (Christoph Hellwig)

   - Fix math notation errors in avg_vruntime comment (Zhan Xusheng)

   - sched/cpufreq: Use %pe format for PTR_ERR() printing
     (zenghongling)"

* tag 'sched-core-2026-02-09' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (64 commits)
  sched: Re-evaluate scheduling when migrating queued tasks out of throttled cgroups
  sched/cpufreq: Use %pe format for PTR_ERR() printing
  sched/rt: Skip currently executing CPU in rto_next_cpu()
  sched/clock: Avoid false sharing for sched_clock_irqtime
  selftests/sched_ext: Add test for DL server total_bw consistency
  selftests/sched_ext: Add test for sched_ext dl_server
  sched/debug: Fix dl_server (re)start conditions
  sched/debug: Add support to change sched_ext server params
  sched_ext: Add a DL server for sched_ext tasks
  sched/debug: Stop and start server based on if it was active
  sched/debug: Fix updating of ppos on server write ops
  sched/deadline: Clear the defer params
  entry: Inline syscall_exit_work() and syscall_trace_enter()
  entry: Add arch_ptrace_report_syscall_entry/exit()
  entry: Rework syscall_exit_to_user_mode_work() for architecture reuse
  entry: Remove unused syscall argument from syscall_trace_enter()
  sched: remove task_struct->faults_disabled_mapping
  sched: Update rq->avg_idle when a task is moved to an idle CPU
  selftests/rseq: Add rseq slice histogram script
  hrtimer: Fix trace oddity
  ...

Provide a new syscall which has the only purpose to yield the CPU after the
kernel granted a time slice extension.

sched_yield() is not suitable for that because it unconditionally
schedules, but the end of the time slice extension is not required to
schedule when the task was already preempted. This also allows to have a
strict check for termination to catch user space invoking random syscalls
including sched_yield() from a time slice extension region.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Link: https://patch.msgid.link/20251215155708.929634896@linutronix.de

Stop definining these privately and instead move them to the uapi
errno.h so that they become canonical instead of copy pasta.

Cc: linux-api@vger.kernel.org
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Link: https://patch.msgid.link/176826402587.3490369.17659117524205214600.stgit@frogsfrogsfrogs
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Christian Brauner <brauner@kernel.org>