diff --git a/sys/kern/kern_sig.c b/sys/kern/kern_sig.c
--- a/sys/kern/kern_sig.c
+++ b/sys/kern/kern_sig.c
@@ -365,6 +365,16 @@
 	SIGFILLSET(fastblock_mask);
 	SIG_CANTMASK(fastblock_mask);
 	ast_register(TDA_SIG, ASTR_UNCOND, 0, ast_sig);
+
+	/*
+	 * TDA_PSELECT is for the case where the signal mask should be restored
+	 * before delivering any signals so that we do not deliver any that are
+	 * blocked by the normal thread mask.  It is mutually exclusive with
+	 * TDA_SIGSUSPEND, which should be used if we *do* want to deliver
+	 * signals that are normally blocked, e.g., if it interrupted our sleep.
+	 */
+	ast_register(TDA_PSELECT, ASTR_ASTF_REQUIRED | ASTR_TDP,
+	    TDP_OLDMASK, ast_sigsuspend);
 	ast_register(TDA_SIGSUSPEND, ASTR_ASTF_REQUIRED | ASTR_TDP,
 	    TDP_OLDMASK, ast_sigsuspend);
 }
diff --git a/sys/sys/param.h b/sys/sys/param.h
--- a/sys/sys/param.h
+++ b/sys/sys/param.h
@@ -73,7 +73,7 @@
  * cannot include sys/param.h and should only be updated here.
  */
 #undef __FreeBSD_version
-#define __FreeBSD_version 1500027
+#define __FreeBSD_version 1500028
 
 /*
  * __FreeBSD_kernel__ indicates that this system uses the kernel of FreeBSD,
diff --git a/sys/sys/proc.h b/sys/sys/proc.h
--- a/sys/sys/proc.h
+++ b/sys/sys/proc.h
@@ -494,6 +494,7 @@
 	TDA_RACCT,
 	TDA_MOD1,		/* For third party use, before signals are */
 	TAD_MOD2,		/* processed .. */
+	TDA_PSELECT,		/* For discarding temporary signal mask */
 	TDA_SIG,
 	TDA_KTRACE,
 	TDA_SUSPEND,