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[#1324] add support for platforms with non native 64 bit atomics #1325

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elfenpiff wants to merge 2 commits into from
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[#1324] add support for platforms with non native 64 bit atomics #1325

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1a2472b
[#1324] Add support for platforms with non-native 64-bit atomic opera…
elfenpiff Jan 27, 2026
cbde9fe
[#1324] Update changelog
elfenpiff Jan 27, 2026
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4 changes: 4 additions & 0 deletions doc/release-notes/iceoryx2-unreleased.md
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Expand Up @@ -18,6 +18,10 @@
[#1289](https://github.com/eclipse-iceoryx/iceoryx2/issues/1289)
* Add source `NodeId` to request and response header
[#1308](https://github.com/eclipse-iceoryx/iceoryx2/issues/1308)
* Add source `NodeId` to request and response header
[#1308](https://github.com/eclipse-iceoryx/iceoryx2/issues/1308)
* Add support for platforms that do not support 64-bit atomics
[#1324](https://github.com/eclipse-iceoryx/iceoryx2/issues/1324)

### Bugfixes

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18 changes: 16 additions & 2 deletions iceoryx2-pal/concurrency-sync/src/atomic.rs
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Expand Up @@ -104,18 +104,32 @@ pub type AtomicI32 = core::sync::atomic::AtomicI32;
pub type AtomicI32 = loom::sync::atomic::AtomicI32;

/// Behaves like [`core::sync::atomic::AtomicI64`]
#[cfg(not(all(test, loom, feature = "std")))]
#[cfg(all(not(all(test, loom, feature = "std")), target_has_atomic = "64"))]
#[allow(clippy::disallowed_types)]
pub type AtomicI64 = core::sync::atomic::AtomicI64;

#[cfg(all(not(all(test, loom, feature = "std")), not(target_has_atomic = "64")))]
#[deprecated(
since = "0.0.1",
note = "This platform does not support native atomic 64-bit operations! iceoryx2 uses a 64-bit atomic based on spinlocks that cannot guarantee lock-free operations. A crash in one process may cause a deadlock in another process."
)]
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@elBoberido elBoberido Jan 27, 2026

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I strongly advice not to do this. All modern (newer than 30 years) CPU architectures not meant for microcontroller support 8 byte CAS also on 32 bit. For uCs, using a spin-lock will lead to deadlocks in common use cases, even if nothing goes wrong. For example, queues are often used to pass data from interrupt service routines to the main loop. iceoryx2 would be ideal for this use case. But with the spin-lock, this can deadlock when a subscriber takes samples in the main loop while a publisher publishes data in the ISR. The warning also does not give any hint that this can happen, because there are no processes on uCs. For anything that can run a process, we already support 8 byte CAS on 32 bit. But even for those use cases, as a user I have no clue what this means. I'm only using publish-subscribe and there is no warning about that, so I'm fine, right?

pub type AtomicI64 = Atomic<i64>;

#[cfg(all(test, loom, feature = "std"))]
pub type AtomicI64 = loom::sync::atomic::AtomicI64;

/// Behaves like [`core::sync::atomic::AtomicU64`]
#[cfg(not(all(test, loom, feature = "std")))]
#[cfg(all(not(all(test, loom, feature = "std")), target_has_atomic = "64"))]
#[allow(clippy::disallowed_types)]
pub type AtomicU64 = core::sync::atomic::AtomicU64;

#[cfg(all(not(all(test, loom, feature = "std")), not(target_has_atomic = "64")))]
#[deprecated(
since = "0.0.1",
note = "This platform does not support native atomic 64-bit operations! iceoryx2 uses a 64-bit atomic based on spinlocks that cannot guarantee lock-free operations. A crash in one process may cause a deadlock in another process."
)]
pub type AtomicU64 = Atomic<u64>;

#[cfg(all(test, loom, feature = "std"))]
pub type AtomicU64 = loom::sync::atomic::AtomicU64;

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