From ddde9e7ee52b6d5c955ce3bbd4bc46eff5e0ed94 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Thu, 3 Feb 2022 01:41:01 +0100
Subject: [PATCH] Kernel: Protect global device map with spinlock instead of
 mutx

---
 Kernel/Devices/Device.h             | 1 -
 Kernel/Devices/DeviceManagement.cpp | 8 ++++----
 Kernel/Devices/DeviceManagement.h   | 2 +-
 3 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/Kernel/Devices/Device.h b/Kernel/Devices/Device.h
index 383584885c..7e9df0186d 100644
--- a/Kernel/Devices/Device.h
+++ b/Kernel/Devices/Device.h
@@ -23,7 +23,6 @@
 #include <Kernel/FileSystem/DeviceFileTypes.h>
 #include <Kernel/FileSystem/File.h>
 #include <Kernel/FileSystem/SysFS.h>
-#include <Kernel/Locking/Mutex.h>
 #include <Kernel/UnixTypes.h>
 
 namespace Kernel {
diff --git a/Kernel/Devices/DeviceManagement.cpp b/Kernel/Devices/DeviceManagement.cpp
index 3315c80e21..cf107a0f68 100644
--- a/Kernel/Devices/DeviceManagement.cpp
+++ b/Kernel/Devices/DeviceManagement.cpp
@@ -49,7 +49,7 @@ DeviceManagement& DeviceManagement::the()
 
 Device* DeviceManagement::get_device(MajorNumber major, MinorNumber minor)
 {
-    return m_devices.with_exclusive([&](auto& map) -> Device* {
+    return m_devices.with([&](auto& map) -> Device* {
         auto it = map.find(encoded_device(major.value(), minor.value()));
         if (it == map.end())
             return nullptr;
@@ -68,7 +68,7 @@ Optional<DeviceEvent> DeviceManagement::dequeue_top_device_event(Badge<DeviceCon
 void DeviceManagement::before_device_removal(Badge<Device>, Device& device)
 {
     u64 device_id = encoded_device(device.major(), device.minor());
-    m_devices.with_exclusive([&](auto& map) -> void {
+    m_devices.with([&](auto& map) -> void {
         VERIFY(map.contains(device_id));
         map.remove(encoded_device(device.major(), device.minor()));
     });
@@ -85,7 +85,7 @@ void DeviceManagement::before_device_removal(Badge<Device>, Device& device)
 void DeviceManagement::after_inserting_device(Badge<Device>, Device& device)
 {
     u64 device_id = encoded_device(device.major(), device.minor());
-    m_devices.with_exclusive([&](auto& map) -> void {
+    m_devices.with([&](auto& map) -> void {
         if (map.contains(device_id)) {
             dbgln("Already registered {},{}: {}", device.major(), device.minor(), device.class_name());
             VERIFY_NOT_REACHED();
@@ -108,7 +108,7 @@ void DeviceManagement::after_inserting_device(Badge<Device>, Device& device)
 
 void DeviceManagement::for_each(Function<void(Device&)> callback)
 {
-    m_devices.with_exclusive([&](auto& map) -> void {
+    m_devices.with([&](auto& map) -> void {
         for (auto& entry : map)
             callback(*entry.value);
     });
diff --git a/Kernel/Devices/DeviceManagement.h b/Kernel/Devices/DeviceManagement.h
index cd9746e6e8..0e849d72bd 100644
--- a/Kernel/Devices/DeviceManagement.h
+++ b/Kernel/Devices/DeviceManagement.h
@@ -77,7 +77,7 @@ private:
     RefPtr<DeviceControlDevice> m_device_control_device;
     // FIXME: Once we have a singleton for managing many sound cards, remove this from here
     NonnullRefPtrVector<CharacterDevice, 1> m_audio_devices;
-    MutexProtected<HashMap<u64, Device*>> m_devices;
+    SpinlockProtected<HashMap<u64, Device*>> m_devices;
 
     mutable Spinlock m_event_queue_lock;
     CircularQueue<DeviceEvent, 100> m_event_queue;