RP2040 missing atomic

[Erhannis]

I'm compiling for an RP2040 and getting a bunch of compile errors I assume are because either I'm missing a library or something's incompatible with atomics somehow.

error[E0599]: no method named `compare_exchange` found for struct `AtomicBool` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/mpsc/async_impl.rs:974:18
    |
973 | /             self.is_split
974 | |                 .compare_exchange(false, true, Ordering::SeqCst, Ordering::SeqCst)
    | |                 -^^^^^^^^^^^^^^^^ method not found in `AtomicBool`
    | |_________________|
    |

error[E0599]: no method named `fetch_add` found for struct `AtomicUsize` in the current scope
    --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/mpsc/async_impl.rs:1304:42
     |
1304 |             test_dbg!(self.core.tx_count.fetch_add(1, Ordering::Relaxed));
     |                                          ^^^^^^^^^ method not found in `AtomicUsize`

error[E0599]: no method named `fetch_sub` found for struct `AtomicUsize` in the current scope
    --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/mpsc/async_impl.rs:1315:45
     |
1315 |             if test_dbg!(self.core.tx_count.fetch_sub(1, Ordering::Release)) > 1 {
     |                                             ^^^^^^^^^ method not found in `AtomicUsize`

error[E0599]: no method named `compare_exchange` found for struct `AtomicBool` in the current scope
  --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util/mutex/spin_impl.rs:43:37
   |
43 |         while test_dbg!(self.locked.compare_exchange(false, true, AcqRel, Acquire)).is_err() {
   |                                     ^^^^^^^^^^^^^^^^ method not found in `AtomicBool`

error[E0599]: no method named `compare_exchange` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/wait/cell.rs:188:14
    |
187 | /         self.lock
188 | |             .compare_exchange(curr, new, success, Acquire)
    | |             -^^^^^^^^^^^^^^^^ method not found in `CachePadded<AtomicUsize>`
    | |_____________|
    |
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  |   pub(crate) struct CachePadded<T>(pub(crate) T);
    |   -------------------------------- method `compare_exchange` not found for this struct

error[E0599]: no method named `fetch_and` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/wait/cell.rs:195:25
    |
195 |         State(self.lock.fetch_and(state, order))
    |                         ^^^^^^^^^ method not found in `CachePadded<AtomicUsize>`
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  | pub(crate) struct CachePadded<T>(pub(crate) T);
    | -------------------------------- method `fetch_and` not found for this struct

error[E0599]: no method named `fetch_or` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/wait/cell.rs:200:25
    |
200 |         State(self.lock.fetch_or(state, order))
    |                         ^^^^^^^^ method not found in `CachePadded<AtomicUsize>`
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  | pub(crate) struct CachePadded<T>(pub(crate) T);
    | -------------------------------- method `fetch_or` not found for this struct

error[E0599]: no method named `compare_exchange` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/wait/queue.rs:193:36
    |
193 |         match test_dbg!(self.state.compare_exchange(WAKING, EMPTY, SeqCst, SeqCst)) {
    |                                    ^^^^^^^^^^^^^^^^ method not found in `CachePadded<AtomicUsize>`
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  | pub(crate) struct CachePadded<T>(pub(crate) T);
    | -------------------------------- method `compare_exchange` not found for this struct

error[E0599]: no method named `compare_exchange_weak` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/wait/queue.rs:227:26
    |
225 |                       match test_dbg!(self
    |  _____________________________________-
226 | |                         .state
227 | |                         .compare_exchange_weak(EMPTY, WAITING, SeqCst, SeqCst))
    | |                         -^^^^^^^^^^^^^^^^^^^^^ method not found in `CachePadded<AtomicUsize>`
    | |_________________________|
    |
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  |   pub(crate) struct CachePadded<T>(pub(crate) T);
    |   -------------------------------- method `compare_exchange_weak` not found for this struct

error[E0599]: no method named `compare_exchange_weak` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/wait/queue.rs:242:26
    |
240 |                       match test_dbg!(self
    |  _____________________________________-
241 | |                         .state
242 | |                         .compare_exchange_weak(WAKING, EMPTY, SeqCst, SeqCst))
    | |                         -^^^^^^^^^^^^^^^^^^^^^ method not found in `CachePadded<AtomicUsize>`
    | |_________________________|
    |
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  |   pub(crate) struct CachePadded<T>(pub(crate) T);
    |   -------------------------------- method `compare_exchange_weak` not found for this struct

error[E0599]: no method named `swap` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/wait/queue.rs:280:48
    |
280 |         let _prev_state = test_dbg!(node.state.swap(WAITING, Release));
    |                                                ^^^^ method not found in `CachePadded<AtomicUsize>`
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  | pub(crate) struct CachePadded<T>(pub(crate) T);
    | -------------------------------- method `swap` not found for this struct

error[E0599]: no method named `compare_exchange_weak` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/wait/queue.rs:380:18
    |
378 |               match test_dbg!(self
    |  _____________________________-
379 | |                 .state
380 | |                 .compare_exchange_weak(state, WAKING, SeqCst, SeqCst))
    | |                 -^^^^^^^^^^^^^^^^^^^^^ method not found in `CachePadded<AtomicUsize>`
    | |_________________|
    |
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  |   pub(crate) struct CachePadded<T>(pub(crate) T);
    |   -------------------------------- method `compare_exchange_weak` not found for this struct

error[E0599]: no method named `compare_exchange` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/wait/queue.rs:404:49
    |
404 |                 if let Err(actual) = self.state.compare_exchange(state, WAKING, SeqCst, SeqCst) {
    |                                                 ^^^^^^^^^^^^^^^^ method not found in `CachePadded<AtomicUsize>`
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  | pub(crate) struct CachePadded<T>(pub(crate) T);
    | -------------------------------- method `compare_exchange` not found for this struct

error[E0599]: no method named `swap` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/wait/queue.rs:446:30
    |
446 |         test_dbg!(self.state.swap(CLOSED, SeqCst));
    |                              ^^^^ method not found in `CachePadded<AtomicUsize>`
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  | pub(crate) struct CachePadded<T>(pub(crate) T);
    | -------------------------------- method `swap` not found for this struct

error[E0599]: no method named `compare_exchange` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/wait/queue.rs:484:39
    |
484 |             let _ = test_dbg!(q.state.compare_exchange(WAITING, EMPTY, SeqCst, SeqCst));
    |                                       ^^^^^^^^^^^^^^^^ method not found in `CachePadded<AtomicUsize>`
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  | pub(crate) struct CachePadded<T>(pub(crate) T);
    | -------------------------------- method `compare_exchange` not found for this struct

error[E0599]: no method named `swap` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/wait/queue.rs:581:48
    |
581 |         let _prev_state = test_dbg!(last.state.swap(new_state, Release));
    |                                                ^^^^ method not found in `CachePadded<AtomicUsize>`
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  | pub(crate) struct CachePadded<T>(pub(crate) T);
    | -------------------------------- method `swap` not found for this struct

error[E0599]: no method named `fetch_or` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/lib.rs:189:29
    |
189 |         test_dbg!(self.tail.fetch_or(self.closed, SeqCst) & self.closed == 0)
    |                             ^^^^^^^^ method not found in `CachePadded<AtomicUsize>`
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  | pub(crate) struct CachePadded<T>(pub(crate) T);
    | -------------------------------- method `fetch_or` not found for this struct

error[E0599]: no method named `compare_exchange_weak` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/lib.rs:236:22
    |
234 |                   match test_dbg!(self
    |  _________________________________-
235 | |                     .tail
236 | |                     .compare_exchange_weak(tail, next_tail, SeqCst, Acquire))
    | |                     -^^^^^^^^^^^^^^^^^^^^^ method not found in `CachePadded<AtomicUsize>`
    | |_____________________|
    |
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  |   pub(crate) struct CachePadded<T>(pub(crate) T);
    |   -------------------------------- method `compare_exchange_weak` not found for this struct

error[E0599]: no method named `fetch_update` found for struct `AtomicUsize` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/lib.rs:248:30
    |
246 |                           test_dbg!(slot
    |  ___________________________________-
247 | |                             .state
248 | |                             .fetch_update(SeqCst, SeqCst, |state| {
    | |                             -^^^^^^^^^^^^ method not found in `AtomicUsize`
    | |_____________________________|
    |

error[E0599]: no method named `fetch_or` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/lib.rs:307:44
    |
307 |             let head = test_dbg!(self.head.fetch_or(0, SeqCst));
    |                                            ^^^^^^^^ method not found in `CachePadded<AtomicUsize>`
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  | pub(crate) struct CachePadded<T>(pub(crate) T);
    | -------------------------------- method `fetch_or` not found for this struct

   Compiling rtic-sync v1.3.0
error[E0599]: no method named `compare_exchange_weak` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/lib.rs:365:22
    |
363 |                   match test_dbg!(self
    |  _________________________________-
364 | |                     .head
365 | |                     .compare_exchange_weak(head, next_head, SeqCst, Acquire))
    | |                     -^^^^^^^^^^^^^^^^^^^^^ method not found in `CachePadded<AtomicUsize>`
    | |_____________________|
    |
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  |   pub(crate) struct CachePadded<T>(pub(crate) T);
    |   -------------------------------- method `compare_exchange_weak` not found for this struct

error[E0599]: no method named `fetch_or` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/lib.rs:396:48
    |
396 |                 let tail = test_dbg!(self.tail.fetch_or(0, SeqCst));
    |                                                ^^^^^^^^ method not found in `CachePadded<AtomicUsize>`
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  | pub(crate) struct CachePadded<T>(pub(crate) T);
    | -------------------------------- method `fetch_or` not found for this struct

error[E0599]: no method named `compare_exchange` found for struct `CachePadded<AtomicUsize>` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/lib.rs:416:43
    |
416 |                 match test_dbg!(self.head.compare_exchange(head, next_head, SeqCst, Acquire)) {
    |                                           ^^^^^^^^^^^^^^^^ method not found in `CachePadded<AtomicUsize>`
    |
   ::: /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/util.rs:19:1
    |
19  | pub(crate) struct CachePadded<T>(pub(crate) T);
    | -------------------------------- method `compare_exchange` not found for this struct

warning: the `-Cinline-threshold` flag is deprecated and does nothing (consider using `-Cllvm-args=--inline-threshold=...`)

error[E0599]: no method named `fetch_and` found for struct `AtomicUsize` in the current scope
   --> /home/erhannis/.cargo/registry/src/index.crates.io-6f17d22bba15001f/thingbuf-0.1.6/src/lib.rs:570:39
    |
570 |             test_dbg!(self.slot.state.fetch_and(!HAS_READER, SeqCst));
    |                                       ^^^^^^^^^ method not found in `AtomicUsize`

   Compiling rtic-monotonics v2.0.3
warning: the `-Cinline-threshold` flag is deprecated and does nothing (consider using `-Cllvm-args=--inline-threshold=...`)

For more information about this error, try `rustc --explain E0599`.
error: could not compile `thingbuf` (lib) due to 24 previous errors
warning: build failed, waiting for other jobs to finish...

I didn't see anything in the docs about extra libraries I should import, so here I am.

[Erhannis]

After some digging and wild guessing, apparently swapping portable-atomic in for core::sync::atomic in a few places was sufficient to get it working? See https://github.com/Erhannis/thingbuf/tree/feature/portable-atomic .

However, you probably don't want to swap it for ALL targets. Maybe an extra feature flag or something?

[EvansJahja]

@Erhannis your patch works for me. Here's hoping to get it merged.

[hawkw]

I believe that portable-atomic will just use stdlib atomics on platforms that support atomic compare-and-swap, and that the intended use is to just use it on all platforms. So, I'd happily merge a PR that just does that --- though note that we will still need to use loom's atomics rather than portable-atomic's when running Loom tests.

[EvansJahja]

Here's my branch, on top of @Erhannis 's feature, I also added portable-atomic-utils for Arc, because some embedded device don't have it. I'm not sure how to make it work with loom...

#96