2 files changed, 22 insertions, 4 deletions

diff --git a/src/cpu/o3/commit.hh b/src/cpu/o3/commit.hh
index 4c9ccf1eb..93c145d5b 100644
--- a/src/cpu/o3/commit.hh
+++ b/src/cpu/o3/commit.hh
@@ -438,9 +438,18 @@ class DefaultCommit
     /** Number of Active Threads */
     ThreadID numThreads;
 
-    /** Is a drain pending. */
+    /** Is a drain pending? Commit is looking for an instruction boundary while
+     * there are no pending interrupts
+     */
     bool drainPending;
 
+    /** Is a drain imminent? Commit has found an instruction boundary while no
+     * interrupts were present or in flight.  This was the last architecturally
+     * committed instruction.  Interrupts disabled and pipeline flushed.
+     * Waiting for structures to finish draining.
+     */
+    bool drainImminent;
+
     /** The latency to handle a trap.  Used when scheduling trap
      * squash event.
      */
diff --git a/src/cpu/o3/commit_impl.hh b/src/cpu/o3/commit_impl.hh
index 347b23359..f0566233c 100644
--- a/src/cpu/o3/commit_impl.hh
+++ b/src/cpu/o3/commit_impl.hh
@@ -104,6 +104,7 @@ DefaultCommit<Impl>::DefaultCommit(O3CPU *_cpu, DerivO3CPUParams *params)
       commitWidth(params->commitWidth),
       numThreads(params->numThreads),
       drainPending(false),
+      drainImminent(false),
       trapLatency(params->trapLatency),
       canHandleInterrupts(true),
       avoidQuiesceLiveLock(false)
@@ -406,6 +407,7 @@ void
 DefaultCommit<Impl>::drainResume()
 {
     drainPending = false;
+    drainImminent = false;
 }
 
 template <class Impl>
@@ -816,8 +818,10 @@ template <class Impl>
 void
 DefaultCommit<Impl>::propagateInterrupt()
 {
+    // Don't propagate intterupts if we are currently handling a trap or
+    // in draining and the last observable instruction has been committed.
     if (commitStatus[0] == TrapPending || interrupt || trapSquash[0] ||
-            tcSquash[0])
+            tcSquash[0] || drainImminent)
         return;
 
     // Process interrupts if interrupts are enabled, not in PAL
@@ -1089,10 +1093,15 @@ DefaultCommit<Impl>::commitInsts()
                     squashAfter(tid, head_inst);
 
                 if (drainPending) {
-                    DPRINTF(Drain, "Draining: %i:%s\n", tid, pc[tid]);
-                    if (pc[tid].microPC() == 0 && interrupt == NoFault) {
+                    if (pc[tid].microPC() == 0 && interrupt == NoFault &&
+                        !thread[tid]->trapPending) {
+                        // Last architectually committed instruction.
+                        // Squash the pipeline, stall fetch, and use
+                        // drainImminent to disable interrupts
+                        DPRINTF(Drain, "Draining: %i:%s\n", tid, pc[tid]);
                         squashAfter(tid, head_inst);
                         cpu->commitDrained(tid);
+                        drainImminent = true;
                     }
                 }