Optimize sighold implementation

This patch simplifies sighold a bit by removing an extra sigprocmask
and using SIG_BLOCK (which union of the current set and the set argument).

Checked on x86_64-linux-gnu.

	* signal/sighold.c (sighold): Optimize implementation.

Signed-off-by: Adhemerval Zanella <adhemerval.zanella@linaro.org>
Reviewed-by: Zack Weinberg <zackw@panix.com>

ChangeLog

@@ -1,5 +1,7 @@
 2017-11-06  Adhemerval Zanella  <adhemerval.zanella@linaro.org>
 
+	* signal/sighold.c (sighold): Optimize implementation.
+
 	* sysdeps/unix/sysv/linux/sigqueue.c (__sigqueue): Asssume
 	__NR_rt_sigqueueinfo.
 

signal/sighold.c

@@ -26,14 +26,8 @@ sighold (int sig)
 {
   sigset_t set;
 
-  /* Retrieve current signal set.  */
-  if (__sigprocmask (SIG_SETMASK, NULL, &set) < 0)
-    return -1;
-
-  /* Add the specified signal.  */
+  sigemptyset (&set);
   if (sigaddset (&set, sig) < 0)
     return -1;
-
-  /* Set the new mask.  */
-  return __sigprocmask (SIG_SETMASK, &set, NULL);
+  return __sigprocmask (SIG_BLOCK, &set, NULL);
 }