Fix deadlock

src/arch/x86/paging.cpp

@@ -172,7 +172,7 @@ int AddressSpace::unmap(void *virt) {
 }
 FDT *AddressSpace::getFdt() {
     if (_fdt.get() == nullptr) {
-        LockGuard l(_lock);
+        LockGuard l(_fdtLock);
         if (_fdt.get() == nullptr) {
             _fdt = UniquePtr(new FDT());
         }

src/arch/x86/paging.hpp

@@ -55,6 +55,7 @@ private:
     uint64_t                             *PML4;
 
     UniquePtr<FDT>                        _fdt;
+    Mutex                                 _fdtLock;
 
     UniquePtr<cgistd::vector<uint64_t *>> _taken_pages;
 

src/kernel/mutex.cpp

@@ -23,6 +23,8 @@ bool Mutex::try_lock() {
 //}
 
 void Mutex::lock() {
+    assert((owner() != Scheduler::cur_task() || !locked));
+
     bool spinned = false;
 
     if (Mutex::try_lock()) {