Kernel: Don't VERIFY that the DMA channel is running on AC'97 interrupt

Fixes #13771; as discussed it's not really a problem to receive an
interrupt while the DMA channel is not running, but we do want to log
it.

Kernel/Devices/Audio/AC97.cpp

@@ -4,6 +4,7 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <AK/Format.h>
 #include <Kernel/Devices/Audio/AC97.h>
 #include <Kernel/Devices/DeviceManagement.h>
 #include <Kernel/Memory/AnonymousVMObject.h>
@@ -274,8 +275,12 @@ ErrorOr<void> AC97::write_single_buffer(UserOrKernelBuffer const& data, size_t o
 void AC97::AC97Channel::handle_dma_stopped()
 {
     dbgln_if(AC97_DEBUG, "AC97 @ {}: channel {}: DMA engine has stopped", m_device.pci_address(), name());
-    VERIFY(m_dma_running);
-    m_dma_running = false;
+    m_dma_running.with([this](auto& dma_running) {
+        // NOTE: QEMU might send spurious interrupts while we're not running, so we don't want to panic here.
+        if (!dma_running)
+            dbgln("AC97 @ {}: received DMA interrupt while it wasn't running", m_device.pci_address());
+        dma_running = false;
+    });
 }
 
 void AC97::AC97Channel::reset()
@@ -288,7 +293,9 @@ void AC97::AC97Channel::reset()
     while ((control_register.in<u8>() & AudioControlRegisterFlag::ResetRegisters) > 0)
         IO::delay(50);
 
-    m_dma_running = false;
+    m_dma_running.with([](auto& dma_running) {
+        dma_running = false;
+    });
 }
 
 void AC97::AC97Channel::set_last_valid_index(u32 buffer_address, u8 last_valid_index)
@@ -310,7 +317,9 @@ void AC97::AC97Channel::start_dma()
     control |= AudioControlRegisterFlag::InterruptOnCompletionEnable;
     control_register.out(control);
 
-    m_dma_running = true;
+    m_dma_running.with([](auto& dma_running) {
+        dma_running = true;
+    });
 }
 
 }

Kernel/Devices/Audio/AC97.h

@@ -13,6 +13,7 @@
 #include <Kernel/Devices/Audio/Controller.h>
 #include <Kernel/Devices/CharacterDevice.h>
 #include <Kernel/Interrupts/IRQHandler.h>
+#include <Kernel/Locking/SpinlockProtected.h>
 
 namespace Kernel {
 
@@ -129,7 +130,10 @@ private:
         {
         }
 
-        bool dma_running() const { return m_dma_running; }
+        bool dma_running() const
+        {
+            return m_dma_running.with([](auto value) { return value; });
+        }
         void handle_dma_stopped();
         StringView name() const { return m_name; }
         IOAddress reg(Register reg) const { return m_channel_base.offset(reg); }
@@ -140,7 +144,7 @@ private:
     private:
         IOAddress m_channel_base;
         AC97& m_device;
-        bool m_dma_running { false };
+        SpinlockProtected<bool> m_dma_running { false };
         StringView m_name;
     };