From 4916b5c1300573c4fca94a1c0caf3a757565add4 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Thu, 11 Mar 2021 14:12:55 +0100
Subject: [PATCH] Kernel: Move process thread lists into protected data

---
 Kernel/FileSystem/ProcFS.cpp |  2 +-
 Kernel/Process.cpp           |  2 ++
 Kernel/Process.h             | 21 ++++++++++++++++++---
 Kernel/Thread.h              |  1 +
 4 files changed, 22 insertions(+), 4 deletions(-)

diff --git a/Kernel/FileSystem/ProcFS.cpp b/Kernel/FileSystem/ProcFS.cpp
index 7829b38e2f..675c3076f7 100644
--- a/Kernel/FileSystem/ProcFS.cpp
+++ b/Kernel/FileSystem/ProcFS.cpp
@@ -1344,7 +1344,7 @@ KResult ProcFSInode::traverse_as_directory(Function<bool(const FS::DirectoryEntr
         auto process = Process::from_pid(pid);
         if (!process)
             return ENOENT;
-        process->for_each_thread([&](Thread& thread) -> IterationDecision {
+        process->for_each_thread([&](const Thread& thread) -> IterationDecision {
             int tid = thread.tid().value();
             callback({ String::number(tid), to_identifier_with_stack(fsid(), tid), 0 });
             return IterationDecision::Continue;
diff --git a/Kernel/Process.cpp b/Kernel/Process.cpp
index 0a01642a2d..3d74cf4dee 100644
--- a/Kernel/Process.cpp
+++ b/Kernel/Process.cpp
@@ -693,6 +693,7 @@ bool Process::create_perf_events_buffer_if_needed()
 
 bool Process::remove_thread(Thread& thread)
 {
+    ProtectedDataMutationScope scope { *this };
     auto thread_cnt_before = m_thread_count.fetch_sub(1, AK::MemoryOrder::memory_order_acq_rel);
     VERIFY(thread_cnt_before != 0);
     ScopedSpinLock thread_list_lock(m_thread_list_lock);
@@ -702,6 +703,7 @@ bool Process::remove_thread(Thread& thread)
 
 bool Process::add_thread(Thread& thread)
 {
+    ProtectedDataMutationScope scope { *this };
     bool is_first = m_thread_count.fetch_add(1, AK::MemoryOrder::memory_order_relaxed) == 0;
     ScopedSpinLock thread_list_lock(m_thread_list_lock);
     m_thread_list.append(thread);
diff --git a/Kernel/Process.h b/Kernel/Process.h
index 0b6be73611..a1f37a3d93 100644
--- a/Kernel/Process.h
+++ b/Kernel/Process.h
@@ -119,6 +119,8 @@ protected:
     u32 m_execpromises { 0 };
     mode_t m_umask { 022 };
     VirtualAddress m_signal_trampoline;
+    Atomic<u32> m_thread_count { 0 };
+    IntrusiveList<Thread, &Thread::m_process_thread_list_node> m_thread_list;
 };
 
 class ProcessBase : public ProtectedProcessBase {
@@ -245,8 +247,11 @@ public:
     static void for_each_in_pgrp(ProcessGroupID, Callback);
     template<typename Callback>
     void for_each_child(Callback);
+
     template<typename Callback>
-    IterationDecision for_each_thread(Callback) const;
+    IterationDecision for_each_thread(Callback);
+    template<typename Callback>
+    IterationDecision for_each_thread(Callback callback) const;
 
     void die();
     void finalize();
@@ -576,8 +581,6 @@ private:
 
     u8 m_termination_status { 0 };
     u8 m_termination_signal { 0 };
-    Atomic<u32> m_thread_count { 0 };
-    mutable IntrusiveList<Thread, &Thread::m_process_thread_list_node> m_thread_list;
     mutable RecursiveSpinLock m_thread_list_lock;
 
     const bool m_is_kernel_process;
@@ -669,6 +672,18 @@ inline IterationDecision Process::for_each_thread(Callback callback) const
     return IterationDecision::Continue;
 }
 
+template<typename Callback>
+inline IterationDecision Process::for_each_thread(Callback callback)
+{
+    ScopedSpinLock thread_list_lock(m_thread_list_lock);
+    for (auto& thread : m_thread_list) {
+        IterationDecision decision = callback(thread);
+        if (decision != IterationDecision::Continue)
+            return decision;
+    }
+    return IterationDecision::Continue;
+}
+
 template<typename Callback>
 inline void Process::for_each_in_pgrp(ProcessGroupID pgid, Callback callback)
 {
diff --git a/Kernel/Thread.h b/Kernel/Thread.h
index 71c6e1526d..19176e136c 100644
--- a/Kernel/Thread.h
+++ b/Kernel/Thread.h
@@ -86,6 +86,7 @@ class Thread
     AK_MAKE_NONMOVABLE(Thread);
 
     friend class Process;
+    friend class ProtectedProcessBase;
     friend class Scheduler;
     friend class ThreadReadyQueue;