From c35fe2ecfe1eba2911d155ad5ade41ca18a765ff Mon Sep 17 00:00:00 2001
From: Felix Morgner <felix.morgner@ost.ch>
Date: Tue, 29 Sep 2026 10:43:50 +0200
Subject: kapi/interrupts: implement IRQ lock

---
 kapi/kapi/interrupts.hpp          |   2 +
 kapi/kapi/interrupts/irq_lock.hpp | 108 ++++++++++++++++++++++++++++++++++++++
 2 files changed, 110 insertions(+)
 create mode 100644 kapi/kapi/interrupts/irq_lock.hpp

(limited to 'kapi')

diff --git a/kapi/kapi/interrupts.hpp b/kapi/kapi/interrupts.hpp
index f9ff22f9..f5b992e2 100644
--- a/kapi/kapi/interrupts.hpp
+++ b/kapi/kapi/interrupts.hpp
@@ -1,5 +1,7 @@
 #ifndef TEACHOS_KAPI_INTERRUPTS_HPP
 #define TEACHOS_KAPI_INTERRUPTS_HPP
+
+#include <kapi/interrupts/irq_lock.hpp>
 #include <kapi/interrupts/state.hpp>
 
 #include <kstd/memory.hpp>
diff --git a/kapi/kapi/interrupts/irq_lock.hpp b/kapi/kapi/interrupts/irq_lock.hpp
new file mode 100644
index 00000000..1b6f6987
--- /dev/null
+++ b/kapi/kapi/interrupts/irq_lock.hpp
@@ -0,0 +1,108 @@
+#ifndef TEACHOS_KAPI_INTERRUPTS_IRQ_LOCK_HPP
+#define TEACHOS_KAPI_INTERRUPTS_IRQ_LOCK_HPP
+
+// IWYU pragma: private, include <kapi/interrupts.hpp>
+
+#include <kapi/interrupts/state.hpp>
+
+#include <kstd/mutex.hpp>
+
+namespace kapi::interrupts
+{
+
+  template<typename = void>
+  struct irq_lock;
+
+  //! @name Kernel-defined API
+  //! @{
+
+  //! A lock to temporarily disable IRQs.
+  template<>
+  struct irq_lock<void>
+  {
+    constexpr irq_lock() = default;
+    constexpr irq_lock(irq_lock const &) = delete;
+    constexpr irq_lock(irq_lock &&) = delete;
+
+    constexpr auto operator=(irq_lock const &) = delete;
+    constexpr auto operator=(irq_lock &&) = delete;
+
+    //! Save the current IRQ state and disable further IRQs.
+    auto lock() -> void
+    {
+      m_old_irq_state = enabled();
+      enabled(false);
+    }
+
+    //! Restore the previously saved IRQ state.
+    auto unlock() -> void
+    {
+      enabled(m_old_irq_state);
+    }
+
+    //! Save the current IRQ state and disable further IRQs.
+    auto try_lock() -> bool
+    {
+      lock();
+      return true;
+    }
+
+  private:
+    bool m_old_irq_state{};
+  };
+
+  //! A lock to temporarily disable IRQs while also acquiring a further lock.
+  template<kstd::basic_lockable BasicLockable>
+  struct irq_lock<BasicLockable> : irq_lock<void>
+  {
+    using lockable_type = BasicLockable;
+
+    explicit irq_lock(BasicLockable & lockable)
+        : m_lockable{lockable}
+    {}
+
+    //! Save the current IRQ state, disable further IRQs, and lock this lock's lockable object.
+    auto lock() -> void
+    {
+      irq_lock<>::lock();
+      m_lockable.lock();
+    }
+
+    //! Unlock this lock's lockable objects and restore the previously saved IRQ state.
+    auto unlock() -> void
+    {
+      m_lockable.unlock();
+      irq_lock<>::unlock();
+    }
+
+    //! Save the current IRQ state, disable further IRQs, and attempt to lock this lock's lockable object.
+    //!
+    //! This function will restore the previous IRQ state if this lock's lockable object cannot be locked.
+    //!
+    //! @return @p true iff. this lock's lockable object could successfully be locked, @p false otherwise.
+    [[nodiscard]] auto try_lock() -> bool
+      requires(kstd::lockable<BasicLockable>)
+    {
+      irq_lock<>::lock();
+      if (m_lockable.try_lock())
+      {
+        return true;
+      }
+      irq_lock<>::unlock();
+      return false;
+    }
+
+  private:
+    lockable_type & m_lockable;
+  };
+
+  //! @}
+
+  irq_lock() -> irq_lock<void>;
+
+  template<kstd::basic_lockable Lockable>
+  irq_lock(Lockable &) -> irq_lock<Lockable>;
+
+}  // namespace kapi::interrupts
+
+#endif
\ No newline at end of file
-- 
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