4 files changed, 9 insertions, 0 deletions
diff --git a/Kernel/Arch/i386/CPU.cpp b/Kernel/Arch/i386/CPU.cpp
index 722f0fd356..afd7b5ecd2 100644
--- a/Kernel/Arch/i386/CPU.cpp
+++ b/Kernel/Arch/i386/CPU.cpp
@@ -545,14 +545,18 @@ void load_task_register(u16 selector)
     asm("ltr %0" ::"r"(selector));
 }
 
+u32 g_in_irq;
+
 void handle_irq(RegisterState regs)
 {
     clac();
+    ++g_in_irq;
     ASSERT(regs.isr_number >= 0x50 && regs.isr_number <= 0x5f);
     u8 irq = (u8)(regs.isr_number - 0x50);
     if (s_irq_handler[irq])
         s_irq_handler[irq]->handle_irq();
     PIC::eoi(irq);
+    --g_in_irq;
 }
 
 void sse_init()
diff --git a/Kernel/Arch/i386/CPU.h b/Kernel/Arch/i386/CPU.h
index 25937ffef2..0bc0cc1d1d 100644
--- a/Kernel/Arch/i386/CPU.h
+++ b/Kernel/Arch/i386/CPU.h
@@ -592,4 +592,6 @@ private:
     u32 m_flags;
 };
 
+extern u32 g_in_irq;
+
 }
diff --git a/Kernel/Arch/i386/PIT.cpp b/Kernel/Arch/i386/PIT.cpp
index fac215a126..c74576747b 100644
--- a/Kernel/Arch/i386/PIT.cpp
+++ b/Kernel/Arch/i386/PIT.cpp
@@ -67,6 +67,7 @@ static u32 s_seconds_since_boot;
 void timer_interrupt_handler(RegisterState regs)
 {
     clac();
+    ++g_in_irq;
     IRQHandlerScope scope(IRQ_TIMER);
     if (++s_ticks_this_second >= TICKS_PER_SECOND) {
         // FIXME: Synchronize with the RTC somehow to prevent drifting apart.
@@ -74,6 +75,7 @@ void timer_interrupt_handler(RegisterState regs)
         s_ticks_this_second = 0;
     }
     Scheduler::timer_tick(regs);
+    --g_in_irq;
 }
 
 namespace PIT {
diff --git a/Kernel/VM/MemoryManager.cpp b/Kernel/VM/MemoryManager.cpp
index 5d9c8430a8..1e71e3172e 100644
--- a/Kernel/VM/MemoryManager.cpp
+++ b/Kernel/VM/MemoryManager.cpp
@@ -281,6 +281,7 @@ PageFaultResponse MemoryManager::handle_page_fault(const PageFault& fault)
 {
     ASSERT_INTERRUPTS_DISABLED();
     ASSERT(Thread::current);
+    ASSERT(!g_in_irq);
 #ifdef PAGE_FAULT_DEBUG
     dbgprintf("MM: handle_page_fault(%w) at V%p\n", fault.code(), fault.vaddr().get());
 #endif