diff --git a/sys/alpha/include/mutex.h b/sys/alpha/include/mutex.h
index 75c64cf3f85a..72d3b7b73401 100644
--- a/sys/alpha/include/mutex.h
+++ b/sys/alpha/include/mutex.h
@@ -60,6 +60,9 @@ extern char STR_SIEN[];
 #define ASS_SIEN(mpp)	MPASS2((mpp)->mtx_saveintr \
 			       != ALPHA_PSL_IPL_HIGH, STR_SIEN)
 
+#define	mtx_legal2block()						\
+	((alpha_pal_rdps() & ALPHA_PSL_IPL_MASK) == ALPHA_PSL_IPL_HIGH)
+
 /*
  * Assembly macros (for internal use only)
  *--------------------------------------------------------------------------
diff --git a/sys/amd64/include/mutex.h b/sys/amd64/include/mutex.h
index 1a8a7b65e7f6..0c4a9eb26ad6 100644
--- a/sys/amd64/include/mutex.h
+++ b/sys/amd64/include/mutex.h
@@ -60,6 +60,8 @@ extern char STR_SIEN[];
 #define	ASS_IDIS	MPASS2((read_eflags() & PSL_I) == 0, STR_IDIS)
 #define ASS_SIEN(mpp)	MPASS2((mpp)->mtx_saveintr & PSL_I, STR_SIEN)
 
+#define	mtx_legal2block()	(read_eflags() & PSL_I)
+
 /*
  * Assembly macros (for internal use only)
  *------------------------------------------------------------------------------
diff --git a/sys/i386/include/mutex.h b/sys/i386/include/mutex.h
index 1a8a7b65e7f6..0c4a9eb26ad6 100644
--- a/sys/i386/include/mutex.h
+++ b/sys/i386/include/mutex.h
@@ -60,6 +60,8 @@ extern char STR_SIEN[];
 #define	ASS_IDIS	MPASS2((read_eflags() & PSL_I) == 0, STR_IDIS)
 #define ASS_SIEN(mpp)	MPASS2((mpp)->mtx_saveintr & PSL_I, STR_SIEN)
 
+#define	mtx_legal2block()	(read_eflags() & PSL_I)
+
 /*
  * Assembly macros (for internal use only)
  *------------------------------------------------------------------------------
diff --git a/sys/ia64/include/mutex.h b/sys/ia64/include/mutex.h
index fe9c646ba112..e3a4a64a24a9 100644
--- a/sys/ia64/include/mutex.h
+++ b/sys/ia64/include/mutex.h
@@ -59,6 +59,8 @@ extern char STR_SIEN[];
 #define	ASS_IDIS	MPASS2(!(save_intr() & IA64_PSR_I), STR_IDIS)
 #define ASS_SIEN(mpp)	MPASS2((mpp)->mtx_saveintr & IA64_PSR_I), STR_SIEN)
 
+#define	mtx_legal2block()	((save_intr() & IA64_PSL_I)
+
 #endif	/* _KERNEL */
 
 #else	/* !LOCORE */
diff --git a/sys/powerpc/include/mutex.h b/sys/powerpc/include/mutex.h
index 75c64cf3f85a..72d3b7b73401 100644
--- a/sys/powerpc/include/mutex.h
+++ b/sys/powerpc/include/mutex.h
@@ -60,6 +60,9 @@ extern char STR_SIEN[];
 #define ASS_SIEN(mpp)	MPASS2((mpp)->mtx_saveintr \
 			       != ALPHA_PSL_IPL_HIGH, STR_SIEN)
 
+#define	mtx_legal2block()						\
+	((alpha_pal_rdps() & ALPHA_PSL_IPL_MASK) == ALPHA_PSL_IPL_HIGH)
+
 /*
  * Assembly macros (for internal use only)
  *--------------------------------------------------------------------------