sched: prevent concurrent wakeups

core/sched.cc

@@ -110,16 +110,14 @@ void thread::prepare_wait()
 
 void thread::wake()
 {
+    // prevent two concurrent wakeups
+    if (!_waiting.exchange(false)) {
+        return;
+    }
     irq_save_lock_type irq_lock;
     with_lock(irq_lock, [this] {
-        if (!_waiting) {
-            return;
-        }
-        _waiting = false;
-        if (!_on_runqueue) {
-            _on_runqueue = true;
-            _cpu->runqueue.push_back(*this);
-        }
+        _on_runqueue = true;
+        _cpu->runqueue.push_back(*this);
     });
 }
 

include/sched.hh

@@ -10,6 +10,7 @@
 #include <boost/intrusive/set.hpp>
 #include <boost/intrusive/list.hpp>
 #include "mutex.hh"
+#include <atomic>
 
 extern "C" {
 void smp_main();
@@ -63,7 +64,7 @@ private:
     thread_state _state;
     thread_control_block* _tcb;
     bool _on_runqueue;
-    bool _waiting;
+    std::atomic_bool _waiting;
     stack_info _stack;
     cpu* _cpu;
     friend void thread_main_c(thread* t);

scripts/loader.py

@@ -128,7 +128,7 @@ class thread_context(object):
         self.new_frame = gdb.newest_frame()
         self.new_frame.select()
         self.running = (not long(thread['_on_runqueue'])
-                        and not long(thread['_waiting']))
+                        and not long(thread['_waiting']['_M_base']['_M_i']))
         self.old_rsp = ulong(gdb.parse_and_eval('$rsp').cast(ulong_type))
         self.old_rip = ulong(gdb.parse_and_eval('$rip').cast(ulong_type))
         self.old_rbp = ulong(gdb.parse_and_eval('$rbp').cast(ulong_type))