[Deepin-Kernel-SIG] [linux 6.6.y] [Upstream] futex: More futex2 bits from mainline-v6.7

[opsiff]

Link: https://lore.kernel.org/all/20230921104505.717750284@noisy.programming.kicks-ass.net/
Hi!

New version of the futex2 patches. Futex2 is a new interface to the same 'old'
futex core. An attempt to get away from the multiplex syscall and add a little
room for extentions.

Changes since v2:

• Rebased to v6.6-rc
• New FUTEX_STRICT flag (Andre)
• Reordered futex_size() helper (tglx)
• Updated some comments (tglx)
• Folded some tags

My plan is to push the first 10 patches (all the syscalls) into
tip/locking/core this afternoon. All those patches have plenty review tags
including from Thomas who is the actual maintainer of this lot :-)

This should be plenty for Jens to get a move on with the io-uring stuff.

I'm holding off on the NUMA bits for now, because I want to write some
userspace for it since there is some confusion on that -- but I seem to keep
getting side-tracked :/

Patches also available at:

git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git locking/core
git://git.kernel.org/pub/scm/linux/kernel/git/peterz/queue.git locking/futex

Where the locking/core thing is the first 10 patches only, and barring Link
tags (which I'll harvest from this posting), will be what I'll push out to tip.

Summary by Sourcery

Introduce futex2 syscall support and shared futex core refactoring to enable new interfaces while preserving existing semantics.

New Features:

• Add futex2 syscalls for wake, wait, requeue, and extend futex_waitv to support futex2 flags and validation.

Enhancements:

• Refactor futex core to use a unified FLAGS_ encoding (including size, shared/NUMA, strict, and clock flags) and centralize timeout handling for reuse across classic futex and futex2 paths.
• Update futex requeue and key-handling APIs to take per-futex flag sets instead of a simple shared/private boolean, improving flexibility and correctness.
• Tighten futex input validation (sizes, masks, and values) and adjust wake/wait paths to honour strict semantics and new flag combinations.
• Plumb the new futex2 syscalls through the generic and architecture-specific syscall tables and compat layers.

[sourcery-ai]

Reviewer's Guide

Backports additional futex2 infrastructure from upstream: it introduces proper FUTEX2 flag and size handling, new futex2 syscalls (wait/wake/requeue), refactors timeout handling and core wait logic to be reusable, and threads the new internal flag representation through the futex core, wait/wake, requeue, PI, and syscall tables across architectures.

Sequence diagram for futex2 futex_wait syscall path

sequenceDiagram
    actor Userspace
    participant sys_futex_wait as sys_futex_wait
    participant futex2_to_flags as futex2_to_flags
    participant futex2_setup_timeout as futex2_setup_timeout
    participant __futex_wait as __futex_wait
    participant futex_wait_setup as futex_wait_setup
    participant futex_wait_queue as futex_wait_queue
    participant futex_unqueue as futex_unqueue

    Userspace->>sys_futex_wait: futex_wait(uaddr, val, mask, flags, timeout, clockid)
    sys_futex_wait->>futex2_to_flags: futex2_to_flags(flags)
    futex2_to_flags-->>sys_futex_wait: internal_flags
    sys_futex_wait->>sys_futex_wait: futex_flags_valid(internal_flags)
    sys_futex_wait->>sys_futex_wait: futex_validate_input(internal_flags, val)
    sys_futex_wait->>sys_futex_wait: futex_validate_input(internal_flags, mask)
    alt timeout provided
        sys_futex_wait->>futex2_setup_timeout: futex2_setup_timeout(timeout, clockid, &to)
        futex2_setup_timeout-->>sys_futex_wait: ret
    end
    sys_futex_wait->>__futex_wait: __futex_wait(uaddr, internal_flags, val, to, mask)
    __futex_wait->>futex_wait_setup: futex_wait_setup(uaddr, val, internal_flags, &q, &hb)
    futex_wait_setup-->>__futex_wait: ret
    __futex_wait->>futex_wait_queue: futex_wait_queue(hb, &q, to)
    futex_wait_queue-->>__futex_wait: wake/timeout/signal
    __futex_wait->>futex_unqueue: futex_unqueue(&q)
    futex_unqueue-->>__futex_wait: result
    __futex_wait-->>sys_futex_wait: ret
    alt timeout used
        sys_futex_wait->>sys_futex_wait: futex2_destroy_timeout(&to)
    end
    sys_futex_wait-->>Userspace: result/errno

Loading

File-Level Changes

Change	Details	Files
Introduce unified internal futex flag and size representation and conversion helpers for legacy futex and futex2 APIs	Add FLAGS_SIZE_, FLAGS_SHARED/CLOCKRT/HAS_TIMEOUT/NUMA/STRICT and futex_size/futex_flags_valid/futex_validate_input helpers in futex.h Add futex_to_flags() and futex2_to_flags() converters for legacy FUTEX_ and new FUTEX2_* user flags Change get_futex_key() signature and implementation to take full flags instead of a boolean shared flag and derive fshared internally Update all futex call sites (wait, wake, wake_op, wait_multiple_setup, requeue, wait_requeue_pi, PI lock/unlock) to pass the new flags representation instead of a bool or FUTEX_PRIVATE_FLAG tests	kernel/futex/futex.h kernel/futex/core.c kernel/futex/waitwake.c kernel/futex/requeue.c kernel/futex/pi.c
Refactor futex wait path to a reusable helper to support both legacy futex and new futex2 wait syscall	Split futex_wait() into a core __futex_wait() that assumes an already-initialized hrtimer_sleeper and returns plain errno, and a thin futex_wait() wrapper that manages timeout setup, teardown, and restart_block state Adjust futex_wait_setup() and callers to work with the new helper and keep restart logic only in the legacy syscall wrapper	kernel/futex/waitwake.c kernel/futex/futex.h
Extend futex_waitv parsing to use futex2-style flags and validation helpers and share timeout setup with new futex2 syscalls	Replace FUTEXV_WAITER_MASK with FUTEX2_VALID_MASK and re-use FUTEX2_* uapi flag space for waitv elements Update futex_parse_waitv() to convert futex2 flags to internal flags via futex2_to_flags(), validate with futex_flags_valid(), and range-check values with futex_validate_input() Introduce futex2_setup_timeout() and futex2_destroy_timeout() helpers and use them in futex_waitv syscall instead of open-coded timeout handling	kernel/futex/syscalls.c kernel/futex/futex.h include/uapi/linux/futex.h
Add futex2 syscalls (futex_wake, futex_wait, futex_requeue) that mirror FUTEX_WAKE_BITSET, FUTEX_WAIT_BITSET, and FUTEX_CMP_REQUEUE semantics using the new flag model	Implement sys_futex_wake() which validates FUTEX2 flags and mask, converts flags via futex2_to_flags(), enforces strict semantics for nr==0 using FLAGS_STRICT, and calls futex_wake() with bitset Implement sys_futex_wait() which validates flags, value, and mask, uses futex2_setup_timeout() for optional absolute timeout, then calls __futex_wait() directly Implement sys_futex_requeue() which parses a two-element futex_waitv array with futex_parse_waitv(), then calls futex_requeue() with per-futex flags and cmpval derived from the first element Wire up new syscalls in syscalls.h, asm-generic unistd, ARM64 compat/unified unistd, sys_ni, and per-arch syscall.tbl files, and bump __NR_syscalls/compat_syscalls Add COND_SYSCALL stubs for the new futex2 syscalls	kernel/futex/syscalls.c kernel/futex/waitwake.c kernel/futex/requeue.c kernel/futex/futex.h include/linux/syscalls.h include/uapi/linux/futex.h include/uapi/asm-generic/unistd.h arch/arm64/include/asm/unistd.h arch/arm64/include/asm/unistd32.h kernel/sys_ni.c arch/*/kernel/syscalls/syscall.tbl
Adjust legacy futex syscall dispatch and requeue semantics to use new flags and support per-futex flag sets	Change do_futex() to derive internal flags via futex_to_flags(op) and use FLAGS_CLOCKRT instead of directly touching FUTEX_CLOCK_REALTIME bits Update FUTEX_REQUEUE, FUTEX_CMP_REQUEUE, and FUTEX_CMP_REQUEUE_PI cases to pass separate flags for source and destination futexes to futex_requeue() Change futex_requeue() itself to take flags1 and flags2, propagate these to get_futex_key() calls for uaddr1/uaddr2, and use flags1 for private/shared retry logic	kernel/futex/syscalls.c kernel/futex/requeue.c

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[Avenger-285714]

So, u know what I would say...

[Copilot]

Pull request overview

This pull request backports additional futex2 pieces by introducing futex2 wake/wait/requeue syscalls and refactoring the futex core to use a unified internal FLAGS_* encoding (size/shared/clock/strict/NUMA) across classic futex and futex2 paths.

Changes:

• Add futex2 syscalls: futex_wake, futex_wait, and futex_requeue, plus wire them into syscall tables and sys_ni fallbacks.
• Refactor futex internals to pass a per-futex flags word (instead of shared/private booleans) into keying, requeue, and wait paths; centralize futex2 timeout setup/teardown.
• Extend/clarify futex2 uapi flag definitions (size bits, NUMA bit, private flag reuse) and add internal helpers for flag conversion and input validation.

Reviewed changes

Copilot reviewed 28 out of 28 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
kernel/sys_ni.c	Add conditional syscall stubs for the new futex2 syscalls.
kernel/futex/waitwake.c	Switch keying to flags, add __futex_wait() helper, and adjust futex_waitv flag handling.
kernel/futex/syscalls.c	Add futex2 syscalls + futex2 timeout helper; convert classic futex op→flags handling.
kernel/futex/requeue.c	Update futex_requeue() API to accept per-futex flag sets; pass flags into keying.
kernel/futex/pi.c	Update PI paths to pass full flags into get_futex_key().
kernel/futex/futex.h	Introduce unified FLAGS_* encoding and conversion/validation helpers; update prototypes.
kernel/futex/core.c	Change get_futex_key() signature to accept flags and derive fshared internally.
include/uapi/linux/futex.h	Define futex2 flag bit layout (size/NUMA/private) and keep historical FUTEX_32.
include/uapi/asm-generic/unistd.h	Allocate syscall numbers for futex2 wake/wait/requeue and bump __NR_syscalls.
include/linux/syscalls.h	Add prototypes for sys_futex_wake, sys_futex_wait, sys_futex_requeue.
arch/xtensa/kernel/syscalls/syscall.tbl	Add futex2 syscall table entries.
arch/x86/entry/syscalls/syscall_64.tbl	Add futex2 syscall table entries.
arch/x86/entry/syscalls/syscall_32.tbl	Add futex2 syscall table entries.
arch/sparc/kernel/syscalls/syscall.tbl	Add futex2 syscall table entries.
arch/sh/kernel/syscalls/syscall.tbl	Add futex2 syscall table entries.
arch/s390/kernel/syscalls/syscall.tbl	Add futex2 syscall table entries.
arch/powerpc/kernel/syscalls/syscall.tbl	Add futex2 syscall table entries.
arch/parisc/kernel/syscalls/syscall.tbl	Add futex2 syscall table entries.
arch/mips/kernel/syscalls/syscall_o32.tbl	Add futex2 syscall table entries.
arch/mips/kernel/syscalls/syscall_n64.tbl	Add futex2 syscall table entries.
arch/mips/kernel/syscalls/syscall_n32.tbl	Add futex2 syscall table entries.
arch/microblaze/kernel/syscalls/syscall.tbl	Add futex2 syscall table entries.
arch/m68k/kernel/syscalls/syscall.tbl	Add futex2 syscall table entries.
arch/ia64/kernel/syscalls/syscall.tbl	Add futex2 syscall table entries.
arch/arm64/include/asm/unistd32.h	Add futex2 compat syscall numbers.
arch/arm64/include/asm/unistd.h	Bump compat syscall count.
arch/arm/tools/syscall.tbl	Add futex2 syscall table entries.
arch/alpha/kernel/syscalls/syscall.tbl	Add futex2 syscall table entries in alpha numbering space.

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