Kernel+Userland: Remove global futexes

We only ever use private futexes, so it doesn't make sense to carry around all the complexity required for global (cross-process) futexes.
akimdi · Aug 16, 2021 · 4226b66 · 4226b66
1 parent 7979b5a
commit 4226b66
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Showing 8 changed files with 48 additions and 188 deletions.
diff --git a/Kernel/API/POSIX/futex.h b/Kernel/API/POSIX/futex.h
@@ -52,9 +52,8 @@ extern "C" {
 #define FUTEX_WAIT_BITSET 9
 #define FUTEX_WAKE_BITSET 10
 
-#define FUTEX_PRIVATE_FLAG (1 << 7)
 #define FUTEX_CLOCK_REALTIME (1 << 8)
-#define FUTEX_CMD_MASK ~(FUTEX_PRIVATE_FLAG | FUTEX_CLOCK_REALTIME)
+#define FUTEX_CMD_MASK ~(FUTEX_CLOCK_REALTIME)
 
 #define FUTEX_BITSET_MATCH_ANY 0xffffffff
 

diff --git a/Kernel/FutexQueue.cpp b/Kernel/FutexQueue.cpp
@@ -10,6 +10,14 @@
 
 namespace Kernel {
 
+FutexQueue::FutexQueue()
+{
+}
+
+FutexQueue::~FutexQueue()
+{
+}
+
 bool FutexQueue::should_add_blocker(Thread::Blocker& b, void* data)
 {
  VERIFY(data != nullptr); // Thread that is requesting to be blocked

diff --git a/Kernel/FutexQueue.h b/Kernel/FutexQueue.h
@@ -14,11 +14,11 @@
 
 namespace Kernel {
 
-class FutexQueue : public Thread::BlockCondition
- , public RefCounted<FutexQueue>
- , public Memory::VMObjectDeletedHandler {
+class FutexQueue
+ : public RefCounted<FutexQueue>
+ , public Thread::BlockCondition {
 public:
- FutexQueue(FlatPtr user_address_or_offset, Memory::VMObject* vmobject = nullptr);
+ FutexQueue();
  virtual ~FutexQueue();
 
  u32 wake_n_requeue(u32, const Function<FutexQueue*()>&, u32, bool&, bool&);
@@ -31,8 +31,6 @@ class FutexQueue : public Thread::BlockCondition
  return Thread::current()->block<Thread::FutexBlocker>(timeout, *this, forward<Args>(args)...);
  }
 
- virtual void vmobject_deleted(Memory::VMObject&) override;
-
  bool queue_imminent_wait();
  void did_remove();
  bool try_remove();
@@ -48,11 +46,6 @@ class FutexQueue : public Thread::BlockCondition
  virtual bool should_add_blocker(Thread::Blocker& b, void* data) override;
 
 private:
- // For private futexes we just use the user space address.
- // But for global futexes we use the offset into the VMObject
- const FlatPtr m_user_address_or_offset;
- WeakPtr<Memory::VMObject> m_vmobject;
- const bool m_is_global;
  size_t m_imminent_waits { 1 }; // We only create this object if we're going to be waiting, so start out with 1
  bool m_was_removed { false };
 };

diff --git a/Kernel/Memory/VMObject.cpp b/Kernel/Memory/VMObject.cpp
@@ -31,13 +31,6 @@ VMObject::VMObject(size_t size)
 
 VMObject::~VMObject()
 {
- {
- ScopedSpinLock lock(m_on_deleted_lock);
- for (auto& it : m_on_deleted)
- it->vmobject_deleted(*this);
- m_on_deleted.clear();
- }
-
  VERIFY(m_regions.is_empty());
 }
 

diff --git a/Kernel/Memory/VMObject.h b/Kernel/Memory/VMObject.h
@@ -7,11 +7,8 @@
 #pragma once
 
 #include <AK/FixedArray.h>
-#include <AK/HashTable.h>
 #include <AK/IntrusiveList.h>
-#include <AK/RefCounted.h>
 #include <AK/RefPtr.h>
-#include <AK/Vector.h>
 #include <AK/Weakable.h>
 #include <Kernel/Forward.h>
 #include <Kernel/Library/ListedRefCounted.h>
@@ -20,12 +17,6 @@
 
 namespace Kernel::Memory {
 
-class VMObjectDeletedHandler {
-public:
- virtual ~VMObjectDeletedHandler() = default;
- virtual void vmobject_deleted(VMObject&) = 0;
-};
-
 class VMObject
  : public ListedRefCounted<VMObject>
  , public Weakable<VMObject> {
@@ -63,17 +54,6 @@ class VMObject
  m_regions.remove(region);
  }
 
- void register_on_deleted_handler(VMObjectDeletedHandler& handler)
- {
- ScopedSpinLock locker(m_on_deleted_lock);
- m_on_deleted.set(&handler);
- }
- void unregister_on_deleted_handler(VMObjectDeletedHandler& handler)
- {
- ScopedSpinLock locker(m_on_deleted_lock);
- m_on_deleted.remove(&handler);
- }
-
 protected:
  explicit VMObject(size_t);
  explicit VMObject(VMObject const&);
@@ -91,9 +71,6 @@ class VMObject
  VMObject& operator=(VMObject&&) = delete;
  VMObject(VMObject&&) = delete;
 
- HashTable<VMObjectDeletedHandler*> m_on_deleted;
- SpinLock<u8> m_on_deleted_lock;
-
  Region::ListInVMObject m_regions;
 
 public: