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Atomic pointer support is an important piece of synchronization
algorithm, e.g. RCU, hence provide the support for that.
Note that instead of relying on atomic_long or the implementation of
`Atomic<usize>`, a new set of helpers (atomic_ptr_*) is introduced for
atomic pointer specifically, this is because ptr2int casting would
lose the provenance of a pointer and even though in theory there are a
few tricks the provenance can be restored, it'll still be a simpler
implementation if C could provide atomic pointers directly. The side
effects of this approach are: we don't have the arithmetic and logical
operations for pointers yet and the current implementation only works
on ARCH_SUPPORTS_ATOMIC_RMW architectures, but these are implementation
issues and can be added later.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Link: https://patch.msgid.link/20260120140503.62804-3-boqun.feng@gmail.com
Link: https://patch.msgid.link/20260303201701.12204-8-boqun@kernel.org
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To support atomic pointers, more cmpxchg helpers will be introduced,
hence define macros to generate these helpers to ease the introduction
of the future helpers.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260117122243.24404-4-boqun.feng@gmail.com
Link: https://patch.msgid.link/20260303201701.12204-6-boqun@kernel.org
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To support atomic pointers, more xchg helpers will be introduced, hence
define macros to generate these helpers to ease the introduction of the
future helpers.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260117122243.24404-3-boqun.feng@gmail.com
Link: https://patch.msgid.link/20260303201701.12204-5-boqun@kernel.org
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To support atomic pointers, more {read,set} helpers will be introduced,
hence define macros to generate these helpers to ease the introduction
of the future helpers.
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260117122243.24404-2-boqun.feng@gmail.com
Link: https://patch.msgid.link/20260303201701.12204-4-boqun@kernel.org
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Add i8/i16 atomic try_cmpxchg_relaxed helpers that call
try_cmpxchg_relaxed() macro implementing atomic try_cmpxchg_relaxed
using architecture-specific instructions.
[boqun: Use try_cmpxchg_relaxed() instead of raw_try_cmpxchg_relaxed()]
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251227115951.1424458-5-fujita.tomonori@gmail.com
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Add i8/i16 atomic try_cmpxchg_release helpers that call
try_cmpxchg_release() macro implementing atomic try_cmpxchg_release
using architecture-specific instructions.
[boqun: Use try_cmpxchg_release() instead of raw_try_cmpxchg_release()]
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251227115951.1424458-4-fujita.tomonori@gmail.com
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Add i8/i16 atomic try_cmpxchg_acquire helpers that call
try_cmpxchg_acquire() macro implementing atomic try_cmpxchg_acquire
using architecture-specific instructions.
[boqun: Use try_cmpxchg_acquire() instead of raw_try_cmpxchg_acquire()]
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251227115951.1424458-3-fujita.tomonori@gmail.com
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Add i8/i16 atomic try_cmpxchg helpers that call try_cmpxchg() macro
implementing atomic try_cmpxchg using architecture-specific
instructions.
[boqun: Add comments explaining CONFIG_ARCH_SUPPORTS_ATOMIC_RMW and use
try_cmpxchg() instead of raw_try_cmpxchg()]
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251227115951.1424458-2-fujita.tomonori@gmail.com
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Add i8/i16 atomic xchg_relaxed helpers that call xchg_relaxed() macro
implementing atomic xchg_relaxed using architecture-specific
instructions.
[boqun: Use xchg_relaxed() instead of raw_xchg_relaxed()]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251223062140.938325-5-fujita.tomonori@gmail.com
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Add i8/i16 atomic xchg_release helpers that call xchg_release() macro
implementing atomic xchg_release using architecture-specific
instructions.
[boqun: Use xchg_release() instead of raw_xchg_release()]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251223062140.938325-4-fujita.tomonori@gmail.com
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Add i8/i16 atomic xchg_acquire helpers that call xchg_acquire() macro
implementing atomic xchg_acquire using architecture-specific
instructions.
[boqun: Use xchg_acquire() instead of raw_xchg_acquire()]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251223062140.938325-3-fujita.tomonori@gmail.com
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Add i8/i16 atomic xchg helpers that call xchg() macro implementing
atomic xchg using architecture-specific instructions.
[boqun: Use xchg() instead of raw_xchg()]
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251223062140.938325-2-fujita.tomonori@gmail.com
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Add READ_ONCE/WRITE_ONCE based helpers for i8 and i16 types to support
relaxed atomic operations in Rust.
While relaxed operations could be implemented purely in Rust using
read_volatile() and write_volatile(), using C's READ_ONCE() and
WRITE_ONCE() macros ensures complete consistency with the kernel
memory model.
These helpers expose different symbol names than their C counterparts
so they are split into atomic_ext.c instead of atomic.c. The symbol
names; the names make the interface Rust/C clear, consistent with
i32/i64.
[boqun: Rename the functions from {load,store} to {read,set} to avoid
future adjustment]
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251211113826.1299077-3-fujita.tomonori@gmail.com
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Add helper functions to expose smp_load_acquire() and
smp_store_release() for i8 and i16 types.
The smp_load_acquire() and smp_store_release() macros require type
information (sizeof) to generate appropriate architecture-specific
memory ordering instructions. Therefore, separate helper functions are
needed for each type size.
These helpers expose different symbol names than their C counterparts
so they are split into atomic_ext.c instead of atomic.c. The symbol
names; atomic_[i8|i16]_read_acquire and atomic_[i8|i16]_set_release
makes the interface Rust/C clear, consistent with i32/i64.
These helpers will be used by the upcoming Atomic<i8> and Atomic<i16>
implementation to provide proper Acquire/Release semantics across all
architectures.
[boqun: Rename the functions from {load,store} to {read,set} to avoid
future adjustment]
Signed-off-by: FUJITA Tomonori <fujita.tomonori@gmail.com>
Reviewed-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
Signed-off-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://patch.msgid.link/20251211113826.1299077-2-fujita.tomonori@gmail.com
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