Merge pull request #9666 from liamwhite/wait-for-me

kernel: fix incorrect locking order in suspension

src/core/hle/kernel/k_condition_variable.cpp

@@ -171,7 +171,7 @@ Result KConditionVariable::WaitForAddress(Handle handle, VAddr addr, u32 value)
         R_UNLESS(owner_thread != nullptr, ResultInvalidHandle);
 
         // Update the lock.
-        cur_thread->SetAddressKey(addr, value);
+        cur_thread->SetUserAddressKey(addr, value);
         owner_thread->AddWaiter(cur_thread);
 
         // Begin waiting.

src/core/hle/kernel/k_light_lock.cpp

@@ -68,7 +68,7 @@ bool KLightLock::LockSlowPath(uintptr_t _owner, uintptr_t _cur_thread) {
 
         // Add the current thread as a waiter on the owner.
         KThread* owner_thread = reinterpret_cast<KThread*>(_owner & ~1ULL);
-        cur_thread->SetAddressKey(reinterpret_cast<uintptr_t>(std::addressof(tag)));
+        cur_thread->SetKernelAddressKey(reinterpret_cast<uintptr_t>(std::addressof(tag)));
         owner_thread->AddWaiter(cur_thread);
 
         // Begin waiting to hold the lock.

src/core/hle/kernel/k_memory_layout.h

@@ -67,9 +67,9 @@ constexpr size_t KernelPageBufferAdditionalSize = 0x33C000;
 constexpr std::size_t KernelResourceSize = KernelPageTableHeapSize + KernelInitialPageHeapSize +
                                            KernelSlabHeapSize + KernelPageBufferHeapSize;
 
-constexpr bool IsKernelAddressKey(VAddr key) {
-    return KernelVirtualAddressSpaceBase <= key && key <= KernelVirtualAddressSpaceLast;
-}
+//! NB: Use KThread::GetAddressKeyIsKernel().
+//! See explanation for deviation of GetAddressKey.
+bool IsKernelAddressKey(VAddr key) = delete;
 
 constexpr bool IsKernelAddress(VAddr address) {
     return KernelVirtualAddressSpaceBase <= address && address < KernelVirtualAddressSpaceEnd;

src/core/hle/kernel/k_thread.cpp

@@ -330,7 +330,7 @@ void KThread::Finalize() {
             KThread* const waiter = std::addressof(*it);
 
             // The thread shouldn't be a kernel waiter.
-            ASSERT(!IsKernelAddressKey(waiter->GetAddressKey()));
+            ASSERT(!waiter->GetAddressKeyIsKernel());
 
             // Clear the lock owner.
             waiter->SetLockOwner(nullptr);
@@ -763,19 +763,6 @@ void KThread::Continue() {
     KScheduler::OnThreadStateChanged(kernel, this, old_state);
 }
 
-void KThread::WaitUntilSuspended() {
-    // Make sure we have a suspend requested.
-    ASSERT(IsSuspendRequested());
-
-    // Loop until the thread is not executing on any core.
-    for (std::size_t i = 0; i < static_cast<std::size_t>(Core::Hardware::NUM_CPU_CORES); ++i) {
-        KThread* core_thread{};
-        do {
-            core_thread = kernel.Scheduler(i).GetSchedulerCurrentThread();
-        } while (core_thread == this);
-    }
-}
-
 Result KThread::SetActivity(Svc::ThreadActivity activity) {
     // Lock ourselves.
     KScopedLightLock lk(activity_pause_lock);
@@ -897,7 +884,7 @@ void KThread::AddWaiterImpl(KThread* thread) {
     }
 
     // Keep track of how many kernel waiters we have.
-    if (IsKernelAddressKey(thread->GetAddressKey())) {
+    if (thread->GetAddressKeyIsKernel()) {
         ASSERT((num_kernel_waiters++) >= 0);
         KScheduler::SetSchedulerUpdateNeeded(kernel);
     }
@@ -911,7 +898,7 @@ void KThread::RemoveWaiterImpl(KThread* thread) {
     ASSERT(kernel.GlobalSchedulerContext().IsLocked());
 
     // Keep track of how many kernel waiters we have.
-    if (IsKernelAddressKey(thread->GetAddressKey())) {
+    if (thread->GetAddressKeyIsKernel()) {
         ASSERT((num_kernel_waiters--) > 0);
         KScheduler::SetSchedulerUpdateNeeded(kernel);
     }
@@ -987,7 +974,7 @@ KThread* KThread::RemoveWaiterByKey(s32* out_num_waiters, VAddr key) {
             KThread* thread = std::addressof(*it);
 
             // Keep track of how many kernel waiters we have.
-            if (IsKernelAddressKey(thread->GetAddressKey())) {
+            if (thread->GetAddressKeyIsKernel()) {
                 ASSERT((num_kernel_waiters--) > 0);
                 KScheduler::SetSchedulerUpdateNeeded(kernel);
             }

src/core/hle/kernel/k_thread.h

@@ -214,8 +214,6 @@ public:
 
     void Continue();
 
-    void WaitUntilSuspended();
-
     constexpr void SetSyncedIndex(s32 index) {
         synced_index = index;
     }
@@ -607,13 +605,30 @@ public:
         return address_key_value;
     }
 
-    void SetAddressKey(VAddr key) {
-        address_key = key;
+    [[nodiscard]] bool GetAddressKeyIsKernel() const {
+        return address_key_is_kernel;
     }
 
-    void SetAddressKey(VAddr key, u32 val) {
+    //! NB: intentional deviation from official kernel.
+    //
+    // Separate SetAddressKey into user and kernel versions
+    // to cope with arbitrary host pointers making their way
+    // into things.
+
+    void SetUserAddressKey(VAddr key) {
+        address_key = key;
+        address_key_is_kernel = false;
+    }
+
+    void SetUserAddressKey(VAddr key, u32 val) {
         address_key = key;
         address_key_value = val;
+        address_key_is_kernel = false;
+    }
+
+    void SetKernelAddressKey(VAddr key) {
+        address_key = key;
+        address_key_is_kernel = true;
     }
 
     void ClearWaitQueue() {
@@ -772,6 +787,7 @@ private:
     bool debug_attached{};
     s8 priority_inheritance_count{};
     bool resource_limit_release_hint{};
+    bool address_key_is_kernel{};
     StackParameters stack_parameters{};
     Common::SpinLock context_guard{};
 

src/core/hle/kernel/kernel.cpp

@@ -1198,27 +1198,34 @@ void KernelCore::Suspend(bool suspended) {
     const bool should_suspend{exception_exited || suspended};
     const auto activity = should_suspend ? ProcessActivity::Paused : ProcessActivity::Runnable;
 
-    std::vector<KScopedAutoObject<KThread>> process_threads;
-    {
-        KScopedSchedulerLock sl{*this};
-
-        if (auto* process = CurrentProcess(); process != nullptr) {
-            process->SetActivity(activity);
-
-            if (!should_suspend) {
-                // Runnable now; no need to wait.
+    //! This refers to the application process, not the current process.
+    KScopedAutoObject<KProcess> process = CurrentProcess();
+    if (process.IsNull()) {
         return;
     }
 
-            for (auto* thread : process->GetThreadList()) {
-                process_threads.emplace_back(thread);
-            }
-        }
-    }
+    // Set the new activity.
+    process->SetActivity(activity);
 
-    // Wait for execution to stop.
-    for (auto& thread : process_threads) {
-        thread->WaitUntilSuspended();
+    // Wait for process execution to stop.
+    bool must_wait{should_suspend};
+
+    // KernelCore::Suspend must be called from locked context, or we
+    // could race another call to SetActivity, interfering with waiting.
+    while (must_wait) {
+        KScopedSchedulerLock sl{*this};
+
+        // Assume that all threads have finished running.
+        must_wait = false;
+
+        for (auto i = 0; i < static_cast<s32>(Core::Hardware::NUM_CPU_CORES); ++i) {
+            if (Scheduler(i).GetSchedulerCurrentThread()->GetOwnerProcess() ==
+                process.GetPointerUnsafe()) {
+                // A thread has not finished running yet.
+                // Continue waiting.
+                must_wait = true;
+            }
+        }
     }
 }