pw_sync_freertos: remove unnecessary atomic in InterruptSpinLock

Changes the internal InterruptSpinLock locked state to use a plain
bool instead of an atomic bool as an atomic is not necessary.

Change-Id: I15fec5bd99861361a2ddbea98192447d09d17e79
Reviewed-on: https://pigweed-review.googlesource.com/c/pigweed/pigweed/+/50464
Pigweed-Auto-Submit: Ewout van Bekkum <ewout@google.com>
Commit-Queue: Ewout van Bekkum <ewout@google.com>
Reviewed-by: Wyatt Hepler <hepler@google.com>

3 files changed, 8 insertions, 10 deletions

diff --git a/pw_sync_freertos/interrupt_spin_lock.cc b/pw_sync_freertos/interrupt_spin_lock.cc
index 656b05c60..825afc473 100644
--- a/pw_sync_freertos/interrupt_spin_lock.cc
+++ b/pw_sync_freertos/interrupt_spin_lock.cc
@@ -27,15 +27,15 @@ void InterruptSpinLock::lock() {
     taskENTER_CRITICAL();
   }
   // We can't deadlock here so crash instead.
-  PW_CHECK(!native_type_.locked.load(std::memory_order_relaxed),
+  PW_CHECK(!native_type_.locked,
            "Recursive InterruptSpinLock::lock() detected");
-  native_type_.locked.store(true, std::memory_order_relaxed);
+  native_type_.locked = true;
 }
 
 bool InterruptSpinLock::try_lock() {
   if (interrupt::InInterruptContext()) {
     UBaseType_t saved_interrupt_mask = taskENTER_CRITICAL_FROM_ISR();
-    if (native_type_.locked.load(std::memory_order_relaxed)) {
+    if (native_type_.locked) {
       // Already locked, restore interrupts and bail out.
       taskEXIT_CRITICAL_FROM_ISR(saved_interrupt_mask);
       return false;
@@ -43,18 +43,18 @@ bool InterruptSpinLock::try_lock() {
     native_type_.saved_interrupt_mask = saved_interrupt_mask;
   } else {  // Task context
     taskENTER_CRITICAL();
-    if (native_type_.locked.load(std::memory_order_relaxed)) {
+    if (native_type_.locked) {
       // ALready locked, restore interrupts and bail out.
       taskEXIT_CRITICAL();
       return false;
     }
   }
-  native_type_.locked.store(true, std::memory_order_relaxed);
+  native_type_.locked = true;
   return true;
 }
 
 void InterruptSpinLock::unlock() {
-  native_type_.locked.store(false, std::memory_order_relaxed);
+  native_type_.locked = false;
   if (interrupt::InInterruptContext()) {
     taskEXIT_CRITICAL_FROM_ISR(native_type_.saved_interrupt_mask);
   } else {  // Task context
diff --git a/pw_sync_freertos/public/pw_sync_freertos/interrupt_spin_lock_inline.h b/pw_sync_freertos/public/pw_sync_freertos/interrupt_spin_lock_inline.h
index 8bbd4cfd8..f086d1549 100644
--- a/pw_sync_freertos/public/pw_sync_freertos/interrupt_spin_lock_inline.h
+++ b/pw_sync_freertos/public/pw_sync_freertos/interrupt_spin_lock_inline.h
@@ -18,7 +18,7 @@
 namespace pw::sync {
 
 constexpr InterruptSpinLock::InterruptSpinLock()
-    : native_type_{.locked{false}, .saved_interrupt_mask = 0} {}
+    : native_type_{.locked = false, .saved_interrupt_mask = 0} {}
 
 inline InterruptSpinLock::native_handle_type
 InterruptSpinLock::native_handle() {
diff --git a/pw_sync_freertos/public/pw_sync_freertos/interrupt_spin_lock_native.h b/pw_sync_freertos/public/pw_sync_freertos/interrupt_spin_lock_native.h
index ac476dc8a..e7f0e8f09 100644
--- a/pw_sync_freertos/public/pw_sync_freertos/interrupt_spin_lock_native.h
+++ b/pw_sync_freertos/public/pw_sync_freertos/interrupt_spin_lock_native.h
@@ -13,14 +13,12 @@
 // the License.
 #pragma once
 
-#include <atomic>
-
 #include "FreeRTOS.h"
 
 namespace pw::sync::backend {
 
 struct NativeInterruptSpinLock {
-  std::atomic<bool> locked;  // Used to detect recursion.
+  bool locked;  // Used to detect recursion.
   UBaseType_t saved_interrupt_mask;
 };
 using NativeInterruptSpinLockHandle = NativeInterruptSpinLock&;