[util] Add thread id to kernel spinlocks

Expose a function __current_thread_id() and use it to record the thread
id on a spinlock waiter when called from the kernel.

src/kernel/objects/thread.cpp

@@ -180,3 +180,10 @@ thread::create_idle_thread(process &kernel, uintptr_t rsp0)
 }
 
 } // namespace obj
+
+uint32_t
+__current_thread_id()
+{
+    cpu_data &cpu = current_cpu();
+    return cpu.thread ? cpu.thread->obj_id() : -1u;
+}

src/kernel/objects/thread.h

@@ -207,3 +207,5 @@ private:
 };
 
 } // namespace obj
+
+extern "C" uint32_t __current_thread_id();

src/libraries/util/util/spinlock.h

@@ -1,8 +1,13 @@
 /// \file spinlock.h
 /// Spinlock types and related defintions
-
 #pragma once
 
+#include <stdint.h>
+
+#ifdef __j6kernel
+extern "C" uint32_t __current_thread_id();
+#endif
+
 namespace util {
 
 /// An MCS based spinlock
@@ -18,6 +23,7 @@ public:
         bool blocked;
         waiter *next;
         char const *where;
+        uint32_t thread;
     };
 
     bool try_acquire(waiter *w);
@@ -36,7 +42,7 @@ public:
             spinlock &lock,
             const char *where = __builtin_FUNCTION()) :
         m_lock(lock),
-        m_waiter {false, nullptr, where},
+        m_waiter {false, nullptr, where, get_thread()},
         m_is_locked {false}
     {
         m_lock.acquire(&m_waiter);
@@ -61,6 +67,14 @@ public:
         }
     }
 
+    inline uint32_t get_thread() const {
+#ifdef __j6kernel
+        return __current_thread_id();
+#else
+        return -1u;
+#endif
+    }
+
 private:
     spinlock &m_lock;
     spinlock::waiter m_waiter;