libc: Fix the definition of SIGRTMAX

After this change, SIGRTMAX will be set to 64 (instead of 32 currently).
Note that this doesn't change the fact that our sigset_t is still defined
as a 32-bit unsigned integer, so most functions that deal with this type
won't support real-time signals though.

Change-Id: Ie1e2f97d646f1664f05a0ac9cac4a43278c3cfa8

libc/bionic/pthread.c

@@ -1858,7 +1858,13 @@ int pthread_sigmask(int how, const sigset_t *set, sigset_t *oset)
      */
     int ret, old_errno = errno;
 
-    ret = __rt_sigprocmask(how, set, oset, _NSIG / 8);
+    /* Use NSIG which corresponds to the number of signals in
+     * our 32-bit sigset_t implementation. As such, this function, or
+     * anything that deals with sigset_t cannot manage real-time signals
+     * (signo >= 32). We might want to introduce sigset_rt_t as an
+     * extension to do so in the future.
+     */
+    ret = __rt_sigprocmask(how, set, oset, NSIG / 8);
     if (ret < 0)
         ret = errno;
 

libc/docs/CHANGES.TXT

@@ -16,6 +16,9 @@ Differences between current and Android 2.3:
 
 - <unistd.h>: Add ftruncate64().
 
+- <signal.h>: Changed the definition of SIGRTMAX to 64. However, note that
+  sigset_t is only 32-bit and cannot deal with real-time signals.
+
 -------------------------------------------------------------------------------
 Differences between Android 2.3 and Android 2.2:
 

libc/include/signal.h

@@ -42,12 +42,15 @@ __BEGIN_DECLS
 
 typedef int sig_atomic_t;
 
-/* crepy NIG / _NSIG handling, just to be safe */
+/* _NSIG is used by the SIGRTMAX definition under <asm/signal.h>, however
-#ifndef NSIG
+ * its definition is part of a #if __KERNEL__ .. #endif block in the original
-#  define NSIG  _NSIG
+ * kernel headers and is thus not part of our cleaned-up versions.
-#endif
+ *
+ * Looking at the current kernel sources, it is defined as 64 for all
+ * architectures except for the 'mips' one which set it to 128.
+ */
 #ifndef _NSIG
-#  define _NSIG  NSIG
+#  define _NSIG  64
 #endif
 
 extern const char * const sys_siglist[];