From 4c6801ad73e296fb34212202f65df703e0206369 Mon Sep 17 00:00:00 2001
From: Abtin Keshavarzian <abtink@google.com>
Date: Wed, 17 Oct 2018 04:23:30 -0700
Subject: [PATCH] [mac] invoke HandleTransmitDone from tasklet in case
 OT_ERROR_ABORT (#3173)

This commit re-uses the `mOperationTask` tasklet (in addition to it
being used for starting a scheduled MAC operation) to invoke the
`HandleTransmitDone()` in case of `OT_ERROR_ABORT` failure. This
ensures that frame retransmission attempt (in case of back-to-back
failures) are not done through the same long call chain.
---
 src/core/mac/mac.cpp | 33 +++++++++++++++++++++++++++++----
 src/core/mac/mac.hpp |  6 ++++--
 2 files changed, 33 insertions(+), 6 deletions(-)

diff --git a/src/core/mac/mac.cpp b/src/core/mac/mac.cpp
index ffe8c45c6..600d2f94c 100644
--- a/src/core/mac/mac.cpp
+++ b/src/core/mac/mac.cpp
@@ -160,10 +160,11 @@ Mac::Mac(Instance &aInstance)
     , mPendingWaitingForData(false)
     , mRxOnWhenIdle(false)
     , mBeaconsEnabled(false)
+    , mTransmitAborted(false)
 #if OPENTHREAD_CONFIG_STAY_AWAKE_BETWEEN_FRAGMENTS
     , mDelaySleep(false)
 #endif
-    , mOperationTask(aInstance, &Mac::PerformOperation, this)
+    , mOperationTask(aInstance, &Mac::HandleOperationTask, this)
     , mMacTimer(aInstance, &Mac::HandleMacTimer, this)
     , mBackoffTimer(aInstance, &Mac::HandleBackoffTimer, this)
     , mReceiveTimer(aInstance, &Mac::HandleReceiveTimer, this)
@@ -755,9 +756,29 @@ void Mac::StartOperation(Operation aOperation)
     }
 }
 
-void Mac::PerformOperation(Tasklet &aTasklet)
+void Mac::HandleOperationTask(Tasklet &aTasklet)
 {
-    aTasklet.GetOwner<Mac>().PerformOperation();
+    aTasklet.GetOwner<Mac>().HandleOperationTask();
+}
+
+void Mac::HandleOperationTask(void)
+{
+    // `mOperationTask` tasklet is used for two separate purposes:
+    //
+    // 1) To invoke `HandleTransmitDone()` from a tasklet with
+    //    `OT_ERROR_ABORT` error.
+    //
+    // 2) To perform a scheduled MAC operation.
+
+    if (mTransmitAborted)
+    {
+        mTransmitAborted = false;
+        HandleTransmitDone(GetOperationFrame(), NULL, OT_ERROR_ABORT);
+    }
+    else
+    {
+        PerformOperation();
+    }
 }
 
 void Mac::PerformOperation(void)
@@ -1242,7 +1263,11 @@ exit:
 
     if (error != OT_ERROR_NONE)
     {
-        HandleTransmitDone(&sendFrame, NULL, OT_ERROR_ABORT);
+        // `HandleTrasnmitDone()` will be invoked from `mOperationTask`
+        // tasklet handler with error `OT_ERROR_ABORT`.
+
+        mTransmitAborted = true;
+        mOperationTask.Post();
     }
 }
 
diff --git a/src/core/mac/mac.hpp b/src/core/mac/mac.hpp
index 96afe0c63..9c73a0775 100644
--- a/src/core/mac/mac.hpp
+++ b/src/core/mac/mac.hpp
@@ -977,6 +977,7 @@ private:
     void    BeginTransmit(void);
     otError HandleMacCommand(Frame &aFrame);
     Frame * GetOperationFrame(void);
+    void    PerformOperation(void);
 
     static void HandleMacTimer(Timer &aTimer);
     void        HandleMacTimer(void);
@@ -984,8 +985,8 @@ private:
     void        HandleBackoffTimer(void);
     static void HandleReceiveTimer(Timer &aTimer);
     void        HandleReceiveTimer(void);
-    static void PerformOperation(Tasklet &aTasklet);
-    void        PerformOperation(void);
+    static void HandleOperationTask(Tasklet &aTasklet);
+    void        HandleOperationTask(void);
 
     void StartCsmaBackoff(void);
 
@@ -1021,6 +1022,7 @@ private:
     bool mPendingWaitingForData : 1;
     bool mRxOnWhenIdle : 1;
     bool mBeaconsEnabled : 1;
+    bool mTransmitAborted : 1;
 #if OPENTHREAD_CONFIG_STAY_AWAKE_BETWEEN_FRAGMENTS
     bool mDelaySleep : 1;
 #endif