diff --git a/c/src/lib/libbsp/powerpc/psim/ChangeLog b/c/src/lib/libbsp/powerpc/psim/ChangeLog
index 0b52f8f9e2..266baca8c4 100644
--- a/c/src/lib/libbsp/powerpc/psim/ChangeLog
+++ b/c/src/lib/libbsp/powerpc/psim/ChangeLog
@@ -1,3 +1,8 @@
+2008-09-05	Joel Sherrill <joel.sherrill@oarcorp.com>
+
+	* shmsupp/lock.c: Disable CPU interrupts when we have the shared memory
+	locked. This is necessary to prevent deadlock.
+
 2008-09-05	Joel Sherrill <joel.sherrill@oarcorp.com>
 
 	* Makefile.am, preinstall.am, shmsupp/getcfg.c, shmsupp/lock.c,
diff --git a/c/src/lib/libbsp/powerpc/psim/shmsupp/lock.c b/c/src/lib/libbsp/powerpc/psim/shmsupp/lock.c
index 204d0188de..12209fb1a2 100644
--- a/c/src/lib/libbsp/powerpc/psim/shmsupp/lock.c
+++ b/c/src/lib/libbsp/powerpc/psim/shmsupp/lock.c
@@ -41,11 +41,14 @@ void Shm_Initialize_lock(
  *  a deadlock condition.
  */
 
+static rtems_interrupt_level level;
+
 void Shm_Lock(
   Shm_Locked_queue_Control *lq_cb
 )
 {
-  (void) PSIM.Semaphore.lock;
+  rtems_interrupt_disable( level );
+    (void) PSIM.Semaphore.lock;
 }
 
 /*
@@ -58,5 +61,6 @@ void Shm_Unlock(
   Shm_Locked_queue_Control *lq_cb
 )
 {
-  (void) PSIM.Semaphore.unlock;
+    (void) PSIM.Semaphore.unlock;
+  rtems_interrupt_enable( level );
 }