Kernel: Switch Process to InstrusiveList from InlineLinkedList

Author: https://github.com/bgianfo
Commit: https://github.com/SerenityOS/serenity/commit/9fccbde371c
Pull-request: https://github.com/SerenityOS/serenity/pull/7859

Kernel/Process.cpp

@@ -40,7 +40,7 @@ static void create_signal_trampoline();
 
 RecursiveSpinLock g_processes_lock;
 static Atomic<pid_t> next_pid;
-READONLY_AFTER_INIT InlineLinkedList<Process>* g_processes;
+READONLY_AFTER_INIT Process::List* g_processes;
 READONLY_AFTER_INIT String* g_hostname;
 READONLY_AFTER_INIT Lock* g_hostname_lock;
 READONLY_AFTER_INIT HashMap<String, OwnPtr<Module>>* g_modules;
@@ -61,7 +61,7 @@ UNMAP_AFTER_INIT void Process::initialize()
     g_modules = new HashMap<String, OwnPtr<Module>>;
 
     next_pid.store(0, AK::MemoryOrder::memory_order_release);
-    g_processes = new InlineLinkedList<Process>;
+    g_processes = new Process::List();
     g_process_groups = new ProcessGroup::List();
     g_hostname = new String("courage");
     g_hostname_lock = new Lock;
@@ -165,9 +165,9 @@ RefPtr<Process> Process::create_user_process(RefPtr<Thread>& first_thread, const
     }
 
     {
-        ScopedSpinLock lock(g_processes_lock);
-        g_processes->prepend(process);
         process->ref();
+        ScopedSpinLock lock(g_processes_lock);
+        g_processes->prepend(*process);
     }
     error = 0;
     return process;
@@ -182,9 +182,9 @@ RefPtr<Process> Process::create_kernel_process(RefPtr<Thread>& first_thread, Str
     first_thread->tss().esp = FlatPtr(entry_data); // entry function argument is expected to be in tss.esp
 
     if (process->pid() != 0) {
-        ScopedSpinLock lock(g_processes_lock);
-        g_processes->prepend(process);
         process->ref();
+        ScopedSpinLock lock(g_processes_lock);
+        g_processes->prepend(*process);
     }
 
     ScopedSpinLock lock(g_scheduler_lock);
@@ -270,8 +270,8 @@ Process::~Process()
 
     {
         ScopedSpinLock processes_lock(g_processes_lock);
-        if (prev() || next())
-            g_processes->remove(this);
+        if (m_list_node.is_in_list())
+            g_processes->remove(*this);
     }
 }
 
@@ -571,17 +571,16 @@ void Process::die()
 
     {
         ScopedSpinLock lock(g_processes_lock);
-        for (auto* process = g_processes->head(); process;) {
-            auto* next_process = process->next();
-            if (process->has_tracee_thread(pid())) {
-                dbgln_if(PROCESS_DEBUG, "Process {} ({}) is attached by {} ({}) which will exit", process->name(), process->pid(), name(), pid());
-                process->stop_tracing();
-                auto err = process->send_signal(SIGSTOP, this);
+        for (auto it = g_processes->begin(); it != g_processes->end();) {
+            auto& process = *it;
+            ++it;
+            if (process.has_tracee_thread(pid())) {
+                dbgln_if(PROCESS_DEBUG, "Process {} ({}) is attached by {} ({}) which will exit", process.name(), process.pid(), name(), pid());
+                process.stop_tracing();
+                auto err = process.send_signal(SIGSTOP, this);
                 if (err.is_error())
-                    dbgln("Failed to send the SIGSTOP signal to {} ({})", process->name(), process->pid());
+                    dbgln("Failed to send the SIGSTOP signal to {} ({})", process.name(), process.pid());
             }
-
-            process = next_process;
         }
     }
 

Kernel/Process.h

@@ -9,7 +9,7 @@
 #include <AK/Checked.h>
 #include <AK/Concepts.h>
 #include <AK/HashMap.h>
-#include <AK/InlineLinkedList.h>
+#include <AK/IntrusiveList.h>
 #include <AK/NonnullOwnPtrVector.h>
 #include <AK/NonnullRefPtrVector.h>
 #include <AK/String.h>
@@ -117,7 +117,6 @@ static_assert(sizeof(ProcessBase) == PAGE_SIZE);
 class Process
     : public ProcessBase
     , public RefCounted<Process>
-    , public InlineLinkedListNode<Process>
     , public Weakable<Process> {
 
     AK_MAKE_NONCOPYABLE(Process);
@@ -125,7 +124,6 @@ class Process
 
     MAKE_ALIGNED_ALLOCATED(Process, PAGE_SIZE);
 
-    friend class InlineLinkedListNode<Process>;
     friend class Thread;
     friend class CoreDump;
 
@@ -569,8 +567,7 @@ private:
             return nullptr;
     }
 
-    Process* m_prev { nullptr };
-    Process* m_next { nullptr };
+    IntrusiveListNode<Process> m_list_node;
 
     String m_name;
 
@@ -649,9 +646,12 @@ private:
     HashMap<String, String> m_coredump_metadata;
 
     NonnullRefPtrVector<Thread> m_threads_for_coredump;
+
+public:
+    using List = IntrusiveList<Process, RawPtr<Process>, &Process::m_list_node>;
 };
 
-extern InlineLinkedList<Process>* g_processes;
+extern Process::List* g_processes;
 extern RecursiveSpinLock g_processes_lock;
 
 template<IteratorFunction<Process&> Callback>
@@ -659,11 +659,11 @@ inline void Process::for_each(Callback callback)
 {
     VERIFY_INTERRUPTS_DISABLED();
     ScopedSpinLock lock(g_processes_lock);
-    for (auto* process = g_processes->head(); process;) {
-        auto* next_process = process->next();
-        if (callback(*process) == IterationDecision::Break)
+    for (auto it = g_processes->begin(); it != g_processes->end();) {
+        auto& process = *it;
+        ++it;
+        if (callback(process) == IterationDecision::Break)
             break;
-        process = next_process;
     }
 }
 
@@ -673,13 +673,13 @@ inline void Process::for_each_child(Callback callback)
     VERIFY_INTERRUPTS_DISABLED();
     ProcessID my_pid = pid();
     ScopedSpinLock lock(g_processes_lock);
-    for (auto* process = g_processes->head(); process;) {
-        auto* next_process = process->next();
-        if (process->ppid() == my_pid || process->has_tracee_thread(pid())) {
-            if (callback(*process) == IterationDecision::Break)
+    for (auto it = g_processes->begin(); it != g_processes->end();) {
+        auto& process = *it;
+        ++it;
+        if (process.ppid() == my_pid || process.has_tracee_thread(pid())) {
+            if (callback(process) == IterationDecision::Break)
                 break;
         }
-        process = next_process;
     }
 }
 
@@ -712,13 +712,13 @@ inline void Process::for_each_in_pgrp(ProcessGroupID pgid, Callback callback)
 {
     VERIFY_INTERRUPTS_DISABLED();
     ScopedSpinLock lock(g_processes_lock);
-    for (auto* process = g_processes->head(); process;) {
-        auto* next_process = process->next();
-        if (!process->is_dead() && process->pgid() == pgid) {
-            if (callback(*process) == IterationDecision::Break)
+    for (auto it = g_processes->begin(); it != g_processes->end();) {
+        auto& process = *it;
+        ++it;
+        if (!process.is_dead() && process.pgid() == pgid) {
+            if (callback(process) == IterationDecision::Break)
                 break;
         }
-        process = next_process;
     }
 }
 

Kernel/Syscalls/fork.cpp

@@ -82,7 +82,7 @@ KResultOr<pid_t> Process::sys$fork(RegisterState& regs)
         }
 
         ScopedSpinLock processes_lock(g_processes_lock);
-        g_processes->prepend(child);
+        g_processes->prepend(*child);
     }
 
     PerformanceManager::add_process_created_event(*child);