kapi: implement a simple, tracked mutex

1 files changed, 55 insertions, 0 deletions

diff --git a/kernel/kapi/tracked_mutex.cpp b/kernel/kapi/tracked_mutex.cpp
new file mode 100644
index 00000000..6608169c
--- /dev/null
+++ b/kernel/kapi/tracked_mutex.cpp
@@ -0,0 +1,55 @@
+#include <kapi/tracked_mutex.hpp>
+
+#include <kapi/cpu.hpp>
+#include <kapi/system.hpp>
+
+#include <atomic>
+
+namespace kapi
+{
+
+  auto tracked_mutex::lock() -> void
+  {
+    auto self = kapi::cpu::current_id();
+    auto expected = kapi::cpu::invalid_id;
+
+    while (!m_owner.compare_exchange_weak(expected, self, std::memory_order::acquire, std::memory_order::relaxed))
+    {
+      if (expected == self)
+      {
+        system::panic("[OS] CPU {} tried to reacquire a mutex it already holds!", self);
+      }
+      expected = kapi::cpu::invalid_id;
+    }
+  }
+
+  auto tracked_mutex::try_lock() -> bool
+  {
+    auto self = kapi::cpu::current_id();
+    auto expected = kapi::cpu::invalid_id;
+
+    if (m_owner.compare_exchange_strong(expected, self, std::memory_order::acquire, std::memory_order::relaxed))
+    {
+      return true;
+    }
+
+    if (expected == self)
+    {
+      system::panic("[OS] CPU {} tried to reacquire a mutex it already holds!", self);
+    }
+
+    return false;
+  }
+
+  auto tracked_mutex::unlock() -> void
+  {
+    auto self = kapi::cpu::current_id();
+    auto expected = self;
+
+    if (!m_owner.compare_exchange_strong(expected, kapi::cpu::invalid_id, std::memory_order::release))
+    {
+      system::panic("[OS] CPU {} released a mutex it did not hold!", self);
+    }
+  }
+
+}  // namespace kapi
\ No newline at end of file