I'm surprised this worked so far. The yield / EAgain mechanism was pretty much broken when using stackless operations.

2 files changed, 12 insertions, 9 deletions

diff --git a/includes/Task.h b/includes/Task.h
index 3e1b9cf..27cb0bc 100644
--- a/includes/Task.h
+++ b/includes/Task.h
@@ -167,10 +167,11 @@ class Task {
     struct ev_loop * getLoop();
     bool isStackless() { return m_stackless; }
   protected:
-    void yield(bool stillRunning = false) throw (GeneralException);
-    void yield(Events::BaseEvent * evt) {
-        waitFor(evt);
-        yield();
+    void yield(Events::BaseEvent * evt = NULL) throw (GeneralException) {
+        if (evt)
+            waitFor(evt);
+        if (yield(false))
+            throw EAgain(NULL);
     }
     virtual void Do() = 0;
     void waitFor(Events::BaseEvent * event);
@@ -190,6 +191,7 @@ class Task {
         m_okayToEAgain = true;
     }
   private:
+    bool yield(bool stillRunning);
     static size_t stackSize() { return 64 * 1024; }
     void setup(TaskMan * taskMan, void * stack);
     static bool needsStacks();
diff --git a/src/Task.cc b/src/Task.cc
index 8e479c3..77217a5 100644
--- a/src/Task.cc
+++ b/src/Task.cc
@@ -144,14 +144,14 @@ void Balau::Task::switchTo() {
     IAssert(m_status != RUNNING, "Task %s at %p is still running... ?", getName(), this);
 }
 
-void Balau::Task::yield(bool stillRunning) throw (GeneralException) {
+bool Balau::Task::yield(bool stillRunning) {
     Printer::elog(E_TASK, "Task %p - %s yielding", this, getName());
     if (stillRunning)
         m_status = YIELDED;
     else
         m_status = SLEEPING;
     if (m_stackless) {
-        throw EAgain(NULL);
+        return true;
     } else {
 #ifndef _WIN32
         coro_transfer(&m_ctx, &m_taskMan->m_returnContext);
@@ -159,6 +159,7 @@ void Balau::Task::yield(bool stillRunning) throw (GeneralException) {
         SwitchToFiber(m_taskMan->m_fiber);
 #endif
     }
+    return false;
 }
 
 Balau::Task * Balau::Task::getCurrentTask() {
@@ -280,10 +281,10 @@ void Balau::Task::operationYield(Events::BaseEvent * evt, enum OperationYieldTyp
         AAssert(t->m_okayToEAgain, "You can't run a stackless operation from a non-okay-to-eagain task.");
     }
 
-    bool gotSignal;
+    bool gotSignal, doEAgain = false;
 
     do {
-        t->yield(evt == NULL);
+        doEAgain = t->yield(evt == NULL);
         static const char * YieldTypeToString[] = {
             "SIMPLE",
             "INTERRUPTIBLE",
@@ -296,7 +297,7 @@ void Balau::Task::operationYield(Events::BaseEvent * evt, enum OperationYieldTyp
     if (!evt)
         return;
 
-    if ((yieldType != SIMPLE) && t->m_okayToEAgain && !gotSignal) {
+    if ((yieldType != SIMPLE) && t->m_okayToEAgain && !gotSignal && doEAgain) {
         Printer::elog(E_TASK, "operation is throwing an exception.");
         throw EAgain(evt);
     }