Merge bitcoin/bitcoin#24069: refactor: replace RecursiveMutex `m_cs_callbacks_pending` with Mutex (and rename)

5574e6ed52d6effd3b7beff0f09b44449202a585 refactor: replace RecursiveMutex `m_callbacks_mutex` with Mutex (Sebastian Falbesoner)
3aa258109e3f3e0b1bfc4f811cbadfd6d516208c scripted-diff: rename `m_cs_callbacks_pending` -> `m_callbacks_mutex` (Sebastian Falbesoner)

Pull request description:

  This PR is related to #19303 and gets rid of the RecursiveMutex `m_cs_callbacks_pending`. All of the critical sections (6 in total) only directly access the guarded elements, i.e. it is not possible that within one section another one is called, and we can use a regular Mutex:

  https://github.com/bitcoin/bitcoin/blob/807169e10b4a18324356ed6ee4d69587b96a7c70/src/scheduler.cpp#L138-L145

  https://github.com/bitcoin/bitcoin/blob/807169e10b4a18324356ed6ee4d69587b96a7c70/src/scheduler.cpp#L152-L160

  https://github.com/bitcoin/bitcoin/blob/807169e10b4a18324356ed6ee4d69587b96a7c70/src/scheduler.cpp#L169-L172

  https://github.com/bitcoin/bitcoin/blob/807169e10b4a18324356ed6ee4d69587b96a7c70/src/scheduler.cpp#L184-L187

  https://github.com/bitcoin/bitcoin/blob/807169e10b4a18324356ed6ee4d69587b96a7c70/src/scheduler.cpp#L197-L199

  https://github.com/bitcoin/bitcoin/blob/807169e10b4a18324356ed6ee4d69587b96a7c70/src/scheduler.cpp#L203-L206

  Also, it is renamed to adapt to the (unwritten) naming convention to use the `_mutex` suffix rather than the `cs_` prefix.

ACKs for top commit:
  hebasto:
    ACK 5574e6ed52d6effd3b7beff0f09b44449202a585, I have reviewed the code and it looks OK, I agree it can be merged.
  w0xlt:
    crACK 5574e6e

Tree-SHA512: ba4b151d956582f4c7183a1d51702b269158fc5e2902c51e6a242aaeb1c72cfcdf398f9ffa42e3072f5aba21a8c493086a5fe7c450c271322da69bd54c37ed1f

2 files changed, 9 insertions, 9 deletions

diff --git a/src/scheduler.cpp b/src/scheduler.cpp
index 378f866e09..0b2ad3c553 100644
--- a/src/scheduler.cpp
+++ b/src/scheduler.cpp
@@ -136,7 +136,7 @@ bool CScheduler::AreThreadsServicingQueue() const
 void SingleThreadedSchedulerClient::MaybeScheduleProcessQueue()
 {
     {
-        LOCK(m_cs_callbacks_pending);
+        LOCK(m_callbacks_mutex);
         // Try to avoid scheduling too many copies here, but if we
         // accidentally have two ProcessQueue's scheduled at once its
         // not a big deal.
@@ -150,7 +150,7 @@ void SingleThreadedSchedulerClient::ProcessQueue()
 {
     std::function<void()> callback;
     {
-        LOCK(m_cs_callbacks_pending);
+        LOCK(m_callbacks_mutex);
         if (m_are_callbacks_running) return;
         if (m_callbacks_pending.empty()) return;
         m_are_callbacks_running = true;
@@ -167,7 +167,7 @@ void SingleThreadedSchedulerClient::ProcessQueue()
         ~RAIICallbacksRunning()
         {
             {
-                LOCK(instance->m_cs_callbacks_pending);
+                LOCK(instance->m_callbacks_mutex);
                 instance->m_are_callbacks_running = false;
             }
             instance->MaybeScheduleProcessQueue();
@@ -182,7 +182,7 @@ void SingleThreadedSchedulerClient::AddToProcessQueue(std::function<void()> func
     assert(m_pscheduler);
 
     {
-        LOCK(m_cs_callbacks_pending);
+        LOCK(m_callbacks_mutex);
         m_callbacks_pending.emplace_back(std::move(func));
     }
     MaybeScheduleProcessQueue();
@@ -194,13 +194,13 @@ void SingleThreadedSchedulerClient::EmptyQueue()
     bool should_continue = true;
     while (should_continue) {
         ProcessQueue();
-        LOCK(m_cs_callbacks_pending);
+        LOCK(m_callbacks_mutex);
         should_continue = !m_callbacks_pending.empty();
     }
 }
 
 size_t SingleThreadedSchedulerClient::CallbacksPending()
 {
-    LOCK(m_cs_callbacks_pending);
+    LOCK(m_callbacks_mutex);
     return m_callbacks_pending.size();
 }
diff --git a/src/scheduler.h b/src/scheduler.h
index 5366a5989c..bb0abfbf7a 100644
--- a/src/scheduler.h
+++ b/src/scheduler.h
@@ -119,9 +119,9 @@ class SingleThreadedSchedulerClient
 private:
     CScheduler* m_pscheduler;
 
-    RecursiveMutex m_cs_callbacks_pending;
-    std::list<std::function<void()>> m_callbacks_pending GUARDED_BY(m_cs_callbacks_pending);
-    bool m_are_callbacks_running GUARDED_BY(m_cs_callbacks_pending) = false;
+    Mutex m_callbacks_mutex;
+    std::list<std::function<void()>> m_callbacks_pending GUARDED_BY(m_callbacks_mutex);
+    bool m_are_callbacks_running GUARDED_BY(m_callbacks_mutex) = false;
 
     void MaybeScheduleProcessQueue();
     void ProcessQueue();