std: use futex-based locks and thread parker on Hermit

Author: joboet

Cargo.lock

@@ -1656,12 +1656,13 @@ dependencies = [
 
 [[package]]
 name = "hermit-abi"
-version = "0.2.0"
+version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1ab7905ea95c6d9af62940f9d7dd9596d54c334ae2c15300c482051292d5637f"
+checksum = "ee512640fe35acbfb4bb779db6f0d80704c2cacfa2e39b601ef3e3f47d1ae4c7"
 dependencies = [
  "compiler_builtins",
  "libc",
+ "rustc-std-workspace-alloc",
  "rustc-std-workspace-core",
 ]
 
@@ -4608,7 +4609,7 @@ dependencies = [
  "dlmalloc",
  "fortanix-sgx-abi",
  "hashbrown",
- "hermit-abi 0.2.0",
+ "hermit-abi 0.2.6",
  "libc",
  "miniz_oxide 0.4.0",
  "object 0.26.2",

library/std/Cargo.toml

@@ -42,7 +42,7 @@ dlmalloc = { version = "0.2.3", features = ['rustc-dep-of-std'] }
 fortanix-sgx-abi = { version = "0.5.0", features = ['rustc-dep-of-std'] }
 
 [target.'cfg(target_os = "hermit")'.dependencies]
-hermit-abi = { version = "0.2.0", features = ['rustc-dep-of-std'] }
+hermit-abi = { version = "0.2.6", features = ['rustc-dep-of-std'] }
 
 [target.wasm32-wasi.dependencies]
 wasi = { version = "0.11.0", features = ['rustc-dep-of-std'], default-features = false }

library/std/src/sys/hermit/condvar.rs

@@ -0,0 +1,39 @@
+use super::abi;
+use crate::ptr::null;
+use crate::sync::atomic::AtomicU32;
+use crate::time::Duration;
+
+pub fn futex_wait(futex: &AtomicU32, expected: u32, timeout: Option<Duration>) -> bool {
+    // Calculate the timeout as a relative timespec.
+    //
+    // Overflows are rounded up to an infinite timeout (None).
+    let timespec = timeout.and_then(|dur| {
+        Some(abi::timespec {
+            tv_sec: dur.as_secs().try_into().ok()?,
+            tv_nsec: dur.subsec_nanos().into(),
+        })
+    });
+
+    let r = unsafe {
+        abi::futex_wait(
+            futex.as_mut_ptr(),
+            expected,
+            timespec.as_ref().map_or(null(), |t| t as *const abi::timespec),
+            abi::FUTEX_RELATIVE_TIMEOUT,
+        )
+    };
+
+    r != -abi::errno::ETIMEDOUT
+}
+
+#[inline]
+pub fn futex_wake(futex: &AtomicU32) -> bool {
+    unsafe { abi::futex_wake(futex.as_mut_ptr(), 1) > 0 }
+}
+
+#[inline]
+pub fn futex_wake_all(futex: &AtomicU32) {
+    unsafe {
+        abi::futex_wake(futex.as_mut_ptr(), i32::MAX);
+    }
+}

library/std/src/sys/hermit/futex.rs

@@ -25,6 +25,7 @@ pub mod cmath;
 pub mod env;
 pub mod fd;
 pub mod fs;
+pub mod futex;
 #[path = "../unsupported/io.rs"]
 pub mod io;
 pub mod memchr;
@@ -45,14 +46,14 @@ pub mod thread_local_dtor;
 pub mod thread_local_key;
 pub mod time;
 
-mod condvar;
-mod mutex;
-mod rwlock;
-
+#[path = "../unix/locks"]
 pub mod locks {
-    pub use super::condvar::*;
-    pub use super::mutex::*;
-    pub use super::rwlock::*;
+    mod futex_condvar;
+    mod futex_mutex;
+    mod futex_rwlock;
+    pub(crate) use futex_condvar::MovableCondvar;
+    pub(crate) use futex_mutex::{MovableMutex, Mutex};
+    pub(crate) use futex_rwlock::{MovableRwLock, RwLock};
 }
 
 use crate::io::ErrorKind;