From 25a4fd1107cf78fd3e0345ff7d291b195a31de3d Mon Sep 17 00:00:00 2001
From: Maxim Poliakovski <maximumspatium@googlemail.com>
Date: Sat, 5 Feb 2022 17:10:57 +0100
Subject: [PATCH] Allow adding timers from timer callbacks.

---
 core/timermanager.cpp | 24 ++++++++++++++++++------
 core/timermanager.h   |  9 +++++----
 cpu/ppc/ppcexec.cpp   |  8 +++++---
 3 files changed, 28 insertions(+), 13 deletions(-)

diff --git a/core/timermanager.cpp b/core/timermanager.cpp
index d6f6187..1ae438e 100644
--- a/core/timermanager.cpp
+++ b/core/timermanager.cpp
@@ -48,7 +48,9 @@ uint32_t TimerManager::add_oneshot_timer(uint64_t timeout, timer_cb cb)
     this->timer_queue.push(timer_desc);
 
     // notify listeners about changes in the timer queue
-    this->notify_timer_changes();
+    if (!this->cb_active) {
+        this->notify_timer_changes();
+    }
 
     return ti->id;
 }
@@ -72,7 +74,9 @@ uint32_t TimerManager::add_cyclic_timer(uint64_t interval, timer_cb cb)
     this->timer_queue.push(timer_desc);
 
     // notify listeners about changes in the timer queue
-    this->notify_timer_changes();
+    if (!this->cb_active) {
+        this->notify_timer_changes();
+    }
 
     return ti->id;
 }
@@ -85,7 +89,9 @@ void TimerManager::cancel_timer(uint32_t id)
     } else {
         this->timer_queue.remove_by_id(id);
     }
-    this->notify_timer_changes();
+    if (!this->cb_active) {
+        this->notify_timer_changes();
+    }
 }
 
 uint64_t TimerManager::process_timers(uint64_t time_now)
@@ -100,8 +106,7 @@ uint64_t TimerManager::process_timers(uint64_t time_now)
     cur_timer = this->timer_queue.top().get();
     while (cur_timer->timeout_ns <= time_now ||
            cur_timer->timeout_ns <= (time_now + MIN_TIMEOUT_NS)) {
-        // invoke timer callback
-        cur_timer->cb();
+        timer_cb cb = cur_timer->cb;
 
         // re-arm cyclic timers
         if (cur_timer->interval_ns) {
@@ -114,6 +119,13 @@ uint64_t TimerManager::process_timers(uint64_t time_now)
             this->timer_queue.pop();
         }
 
+        this->cb_active = true;
+
+        // invoke timer callback
+        cb();
+
+        this->cb_active = false;
+
         // process next timer
         if (this->timer_queue.empty()) {
             return 0ULL;
@@ -124,4 +136,4 @@ uint64_t TimerManager::process_timers(uint64_t time_now)
 
     // return time slice in nanoseconds until next timer's expiry
     return cur_timer->timeout_ns - time_now;
-}
\ No newline at end of file
+}
diff --git a/core/timermanager.h b/core/timermanager.h
index 9b56660..ec02738 100644
--- a/core/timermanager.h
+++ b/core/timermanager.h
@@ -82,7 +82,7 @@ public:
         return timer_manager;
     };
 
-    // callback ´for retrieving current time
+    // callback for retrieving current time
     void set_time_now_cb(const function<uint64_t()> &cb) {
         this->get_time_now = cb;
     };
@@ -103,13 +103,14 @@ private:
     static TimerManager* timer_manager;
     TimerManager(){}; // private constructor to implement a singleton
 
-    uint32_t id = 0;
-
     // timer queue
     my_priority_queue<shared_ptr<TimerInfo>, vector<shared_ptr<TimerInfo>>, MyGtComparator> timer_queue;
 
     function<uint64_t()>   get_time_now;
     function<void()>       notify_timer_changes;
+
+    uint32_t    id = 0;
+    bool        cb_active = false; // true if a timer callback is executing
 };
 
-#endif // TIMER_MANAGER_H
\ No newline at end of file
+#endif // TIMER_MANAGER_H
diff --git a/cpu/ppc/ppcexec.cpp b/cpu/ppc/ppcexec.cpp
index 258af30..0fde991 100644
--- a/cpu/ppc/ppcexec.cpp
+++ b/cpu/ppc/ppcexec.cpp
@@ -319,7 +319,11 @@ uint64_t process_events()
 void force_cycle_counter_reload()
 {
     // tell the interpreter loop to reload cycle counter
-    bb_kind = BB_end_kind::BB_TIMER;
+    if (bb_kind == BB_end_kind::BB_NONE || bb_kind == BB_end_kind::BB_TIMER) {
+        bb_kind = BB_end_kind::BB_TIMER;
+    } else {
+        ABORT_F("PPCEXEC: attempt to override basic block type %d", bb_kind);
+    }
 }
 
 /** Execute PPC code as long as power is on. */
@@ -412,7 +416,6 @@ static void ppc_exec_inner()
                 max_cycles = process_events();
             }
 
-            //if (eb_last) {
             if (bb_kind != BB_end_kind::BB_NONE) { // execution block ended ?
                 if (!power_on)
                     break;
@@ -611,7 +614,6 @@ static void ppc_exec_until_inner(const uint32_t goal_addr)
                 max_cycles = process_events();
             }
 
-            //if (eb_last) {
             if (bb_kind != BB_end_kind::BB_NONE) { // execution block ended ?
                 // reload cycle counter if requested
                 if (bb_kind == BB_end_kind::BB_TIMER) {