diff --git a/documentation/RELEASE_NOTES.md b/documentation/RELEASE_NOTES.md
index 617049dfa..eb9ba33fa 100644
--- a/documentation/RELEASE_NOTES.md
+++ b/documentation/RELEASE_NOTES.md
@@ -26,6 +26,9 @@ The IOC needs to run with SCHED_FIFO engaged.
 Support for Posix implementations before POSIX.1-2001 (_XOPEN_SOURCE < 500,
 glibc version < 2.3.3) has been dropped.
 
+The epicsMutexShowAll() function (available through IOC shell)
+will print "PI is enabled" if both libc and kernel support is present.
+
 ### Add epicsStrSimilarity()
 
 Add epicsStrSimilarity() to epicsString.h which uses edit distance as an approximate comparison.
diff --git a/modules/libcom/src/osi/epicsMutex.cpp b/modules/libcom/src/osi/epicsMutex.cpp
index 1c15583a6..0a63a6f33 100644
--- a/modules/libcom/src/osi/epicsMutex.cpp
+++ b/modules/libcom/src/osi/epicsMutex.cpp
@@ -17,6 +17,7 @@
  * currently safe to convert a thread id to a thread name because
  * the thread may have exited making the thread id invalid.
  */
+#define EPICS_PRIVATE_API
 
 #include <new>
 
@@ -223,6 +224,7 @@ void epicsStdCall epicsMutexShowAll(int onlyLocked,unsigned  int level)
 
     printf("ellCount(&mutexList) %d ellCount(&freeList) %d\n",
         ellCount(&mutexList),ellCount(&freeList));
+    epicsMutexOsdShowAll();
     epicsMutexLockStatus lockStat =
         epicsMutexOsdLock(epicsMutexGlobalLock);
     assert ( lockStat == epicsMutexLockOK );
diff --git a/modules/libcom/src/osi/epicsMutex.h b/modules/libcom/src/osi/epicsMutex.h
index fec4de9f8..fc47eda0c 100644
--- a/modules/libcom/src/osi/epicsMutex.h
+++ b/modules/libcom/src/osi/epicsMutex.h
@@ -258,6 +258,9 @@ void epicsMutexOsdUnlock(struct epicsMutexOSD *);
 epicsMutexLockStatus epicsMutexOsdLock(struct epicsMutexOSD *);
 epicsMutexLockStatus epicsMutexOsdTryLock(struct epicsMutexOSD *);
 void epicsMutexOsdShow(struct epicsMutexOSD *,unsigned  int level);
+#ifdef EPICS_PRIVATE_API
+void epicsMutexOsdShowAll(void);
+#endif
 
 #ifdef __cplusplus
 }
diff --git a/modules/libcom/src/osi/os/RTEMS/osdMutex.c b/modules/libcom/src/osi/os/RTEMS/osdMutex.c
index 80e7872ff..44adf2f6e 100644
--- a/modules/libcom/src/osi/os/RTEMS/osdMutex.c
+++ b/modules/libcom/src/osi/os/RTEMS/osdMutex.c
@@ -22,6 +22,8 @@
 #include <rtems.h>
 #include <rtems/error.h>
 
+#define EPICS_PRIVATE_API
+
 #include "epicsStdio.h"
 #include "epicsMutex.h"
 #include "epicsEvent.h"
@@ -193,3 +195,5 @@ LIBCOM_API void epicsMutexOsdShow(struct epicsMutexOSD * id,unsigned int level)
 #endif
     epicsEventShow ((epicsEventId)id,level);
 }
+
+void epicsMutexOsdShowAll(void) {}
diff --git a/modules/libcom/src/osi/os/WIN32/osdMutex.c b/modules/libcom/src/osi/os/WIN32/osdMutex.c
index 596d5af65..405a9c741 100644
--- a/modules/libcom/src/osi/os/WIN32/osdMutex.c
+++ b/modules/libcom/src/osi/os/WIN32/osdMutex.c
@@ -42,6 +42,8 @@
 #endif
 #include <windows.h>
 
+#define EPICS_PRIVATE_API
+
 #include "libComAPI.h"
 #include "epicsMutex.h"
 #include "epicsAssert.h"
@@ -176,3 +178,5 @@ void epicsMutexOsdShow ( epicsMutexOSD * pSem, unsigned level )
     }
 }
 
+void epicsMutexOsdShowAll(void) {}
+
diff --git a/modules/libcom/src/osi/os/posix/osdMutex.c b/modules/libcom/src/osi/os/posix/osdMutex.c
index 6279c57f3..83833f85c 100644
--- a/modules/libcom/src/osi/os/posix/osdMutex.c
+++ b/modules/libcom/src/osi/os/posix/osdMutex.c
@@ -24,11 +24,14 @@
 #include <unistd.h>
 #include <pthread.h>
 
+#define EPICS_PRIVATE_API
+
 #include "epicsMutex.h"
 #include "osdPosixMutexPriv.h"
 #include "cantProceed.h"
 #include "epicsTime.h"
 #include "errlog.h"
+#include "epicsStdio.h"
 #include "epicsAssert.h"
 
 #define checkStatus(status,message) \
@@ -188,3 +191,14 @@ void epicsMutexOsdShow(struct epicsMutexOSD * pmutex, unsigned int level)
      */
     printf("    pthread_mutex_t* uaddr=%p\n", &pmutex->lock);
 }
+
+void epicsMutexOsdShowAll(void)
+{
+    int proto = -1;
+    int ret = pthread_mutexattr_getprotocol(&globalAttrRecursive, &proto);
+    if(ret) {
+        printf("PI maybe not enabled: %d\n", ret);
+    } else {
+        printf("PI is%s enabled\n", proto==PTHREAD_PRIO_INHERIT ? "" : " not");
+    }
+}
diff --git a/modules/libcom/src/osi/os/vxWorks/osdMutex.c b/modules/libcom/src/osi/os/vxWorks/osdMutex.c
index 4b439a1f1..d772bf2dd 100644
--- a/modules/libcom/src/osi/os/vxWorks/osdMutex.c
+++ b/modules/libcom/src/osi/os/vxWorks/osdMutex.c
@@ -20,6 +20,7 @@
 /* The following not defined in an vxWorks header */
 int sysClkRateGet(void);
 
+#define EPICS_PRIVATE_API
 
 #include "epicsMutex.h"
 
@@ -47,3 +48,5 @@ void epicsMutexOsdShow(struct epicsMutexOSD * id,unsigned int level)
 {
     semShow((SEM_ID)id,level);
 }
+
+void epicsMutexOsdShowAll(void) {}