diff --git a/libguile/debug.c b/libguile/debug.c
index 107b5d4..6f47354 100644
--- a/libguile/debug.c
+++ b/libguile/debug.c
@@ -263,3 +263,4 @@ scm_init_debug ()
   c-file-style: "gnu"
   End:
 */
+int dpe = 0;
diff --git a/libguile/debugx.h b/libguile/debugx.h
new file mode 100644
index 0000000..b39a7bb
--- /dev/null
+++ b/libguile/debugx.h
@@ -0,0 +1,35 @@
+/*
+vim: set ts=8 sts=2 sw=2 noexpandtab filetype=c:
+*/
+#include <unistd.h>
+#include <time.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <stdlib.h>
+
+extern int dpe;
+
+#define DEBUG_PRINTF( cond, format, args... ) \
+  if ( cond )\
+  { \
+    struct timespec l_timespec; \
+    struct tm l_tm; \
+    char date_time_buf[32];\
+    char __db_buffer[8*1024]; \
+    int written = -1; \
+    clock_gettime( CLOCK_REALTIME, &l_timespec ); \
+    \
+    localtime_r(&(l_timespec.tv_sec), &l_tm); \
+    \
+    strftime( date_time_buf, 32, "%Y-%m-%dT%H:%M:%S", &l_tm );\
+    \
+    \
+    written = snprintf( __db_buffer, 8*1024, "%s.%09li [%08u:%08u:%010u] DEBUG_VAR [%s:%i:%s] "format"\n", \
+      date_time_buf, l_timespec.tv_nsec, \
+      ( unsigned int )( getpid() ), ( unsigned int )( getppid() ), ( unsigned int )( pthread_self() ), \
+      __FILE__, __LINE__, __FUNCTION__, \
+      ##args ); \
+    write( fileno( stderr ), __db_buffer, written ); \
+  } \
+
+
diff --git a/libguile/init.c b/libguile/init.c
index b320360..33340ce 100644
--- a/libguile/init.c
+++ b/libguile/init.c
@@ -17,6 +17,9 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  * 02110-1301 USA
  */
+/*
+vim: set ts=8 sts=2 sw=2 noexpandtab filetype=c:
+*/
 
 
 
@@ -304,6 +307,7 @@ static void *invoke_main_func(void *body_data);
    allocate.  So, scm_boot_guile function exits, rather than
    returning, to discourage people from making that mistake.  */
 
+#include "libguile/debugx.h"
 
 void
 scm_boot_guile (int argc, char ** argv, void (*main_func) (), void *closure)
@@ -380,6 +384,7 @@ scm_i_init_guile (void *base)
 {
   if (scm_initialized_p)
     return;
+  dpe = ( getenv( "DEBUG_PRINTF_ENABLE" ) != NULL );
 
   scm_storage_prehistory ();
   scm_threads_prehistory (base);  /* requires storage_prehistory */
diff --git a/libguile/threads.c b/libguile/threads.c
index 15e4919..702ce37 100644
--- a/libguile/threads.c
+++ b/libguile/threads.c
@@ -17,6 +17,9 @@
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  * 02110-1301 USA
  */
+/*
+vim: set ts=8 sts=2 sw=2 noexpandtab filetype=c:
+*/
 
 
 
@@ -64,6 +67,7 @@
 #include "libguile/scmsigs.h"
 #include "libguile/strings.h"
 #include "libguile/weaks.h"
+#include "libguile/debugx.h"
 
 #include <full-read.h>
 
@@ -458,7 +462,10 @@ block_self (SCM queue, SCM sleep_object, scm_i_pthread_mutex_t *mutex,
 	 happened above.
       */
       if (remqueue (queue, q_handle) && err == 0)
+        {
+          DEBUG_PRINTF( dpe, "[ waittime = %p, errno = %i, errno_string = %s ]", waittime, err, strerror( err ) );
 	err = EINTR;
+        }
       t->block_asyncs--;
       scm_i_reset_sleep (t);
     }
@@ -1406,6 +1413,8 @@ fat_mutex_lock (SCM mutex, scm_t_timespec *timeout, SCM owner, int *ret)
     {
       if (m->level == 0)
 	{
+          DEBUG_PRINTF( dpe, "mutex = %lu : m->level = %i : owner = %lu -> %lu",
+            SCM_UNPACK( mutex ), m->level, SCM_UNPACK( m->owner ), SCM_UNPACK( new_owner ) );
 	  m->owner = new_owner;
 	  m->level++;
 
@@ -1432,6 +1441,8 @@ fat_mutex_lock (SCM mutex, scm_t_timespec *timeout, SCM owner, int *ret)
 	}
       else if (SCM_I_IS_THREAD (m->owner) && scm_c_thread_exited_p (m->owner))
 	{
+          DEBUG_PRINTF( dpe, "mutex = %lu : m->level = %i : owner = %lu -> %lu",
+            SCM_UNPACK( mutex ), m->level, SCM_UNPACK( m->owner ), SCM_UNPACK( new_owner ) );
 	  m->owner = new_owner;
 	  err = scm_cons (scm_abandoned_mutex_error_key,
 			  scm_from_locale_string ("lock obtained on abandoned "
@@ -1589,6 +1600,8 @@ fat_mutex_unlock (SCM mutex, SCM cond,
 	  if (!m->unchecked_unlock)
 	    {
 	      scm_i_pthread_mutex_unlock (&m->lock);
+              DEBUG_PRINTF( dpe, "mutex = %lu : t->handle = %lu : m->level = %i : owner = %lu -> -1",
+                SCM_UNPACK( mutex ), SCM_UNPACK( t->handle ), m->level, SCM_UNPACK( owner ) );
 	      scm_misc_error (NULL, "mutex not locked", SCM_EOL);
 	    }
 	  owner = t->handle;
@@ -1596,6 +1609,8 @@ fat_mutex_unlock (SCM mutex, SCM cond,
       else if (!m->allow_external_unlock)
 	{
 	  scm_i_pthread_mutex_unlock (&m->lock);
+          DEBUG_PRINTF( dpe, "mutex = %lu : t->handle = %lu : m->level = %i : owner = %lu -> -1",
+            SCM_UNPACK( mutex ), SCM_UNPACK( t->handle ), m->level, SCM_UNPACK( owner ) );
 	  scm_misc_error (NULL, "mutex not locked by current thread", SCM_EOL);
 	}
     }
@@ -1619,6 +1634,8 @@ fat_mutex_unlock (SCM mutex, SCM cond,
 	  t->block_asyncs++;
 
 	  err = block_self (c->waiting, cond, &m->lock, waittime);
+          DEBUG_PRINTF( dpe, "mutex = %lu : t->handle = %lu : m->level = %i : owner = %lu -> %lu [ relock = %i, err = %i, errstr = %s ]",
+            SCM_UNPACK( mutex ), SCM_UNPACK( t->handle ), m->level, SCM_UNPACK( owner ), SCM_UNPACK( m->owner ), relock, err, strerror( err ) );
 	  scm_i_pthread_mutex_unlock (&m->lock);
 
 	  if (err == 0)
@@ -1662,6 +1679,8 @@ fat_mutex_unlock (SCM mutex, SCM cond,
 	  /* Change the owner of MUTEX.  */
 	  t->mutexes = scm_delq_x (mutex, t->mutexes);
 	  m->owner = unblock_from_queue (m->waiting);
+          DEBUG_PRINTF( dpe, "mutex = %lu : t->handle = %lu : m->level = %i : owner = %lu -> %lu [ relock = %i ]",
+            SCM_UNPACK( mutex ), SCM_UNPACK( t->handle ), m->level, SCM_UNPACK( owner ), SCM_UNPACK( m->owner ), relock );
 	}
 
       scm_i_pthread_mutex_unlock (&m->lock);