Fix PTHREAD_THREADS_MAX.

We don't have a compile-time limit on the number of threads,
and we don't have a definite run-time limit either.

Bug: http://b/27617302
Change-Id: I6a6fe083e7b655d24eb9e7ef7f3e0280d483080b
diff --git a/libc/bionic/sysconf.cpp b/libc/bionic/sysconf.cpp
index 125b3c9..cff6288 100644
--- a/libc/bionic/sysconf.cpp
+++ b/libc/bionic/sysconf.cpp
@@ -124,8 +124,8 @@
     case _SC_THREAD_DESTRUCTOR_ITERATIONS: return PTHREAD_DESTRUCTOR_ITERATIONS;
     case _SC_THREAD_KEYS_MAX:   return PTHREAD_KEYS_MAX;
     case _SC_THREAD_STACK_MIN:    return PTHREAD_STACK_MIN;
-    case _SC_THREAD_THREADS_MAX:  return PTHREAD_THREADS_MAX;
-    case _SC_TTY_NAME_MAX:        return 32;  // Seems default on linux.
+    case _SC_THREAD_THREADS_MAX:  return -1; // No specific limit.
+    case _SC_TTY_NAME_MAX:        return 32; // Seems default on linux.
     case _SC_THREADS:             return _POSIX_THREADS;
     case _SC_THREAD_ATTR_STACKADDR:   return _POSIX_THREAD_ATTR_STACKADDR;
     case _SC_THREAD_ATTR_STACKSIZE:   return _POSIX_THREAD_ATTR_STACKSIZE;
diff --git a/libc/include/sys/limits.h b/libc/include/sys/limits.h
index be79cf3..f84253e 100644
--- a/libc/include/sys/limits.h
+++ b/libc/include/sys/limits.h
@@ -120,8 +120,11 @@
 #define  _XOPEN_VERSION             700       /* by Posix definition */
 
 
-#define PTHREAD_DESTRUCTOR_ITERATIONS 4     // >= _POSIX_THREAD_DESTRUCTOR_ITERATIONS
-#define PTHREAD_KEYS_MAX              128   // >= _POSIX_THREAD_KEYS_MAX
-#define PTHREAD_THREADS_MAX           2048  // bionic has no specific limit
+/* >= _POSIX_THREAD_DESTRUCTOR_ITERATIONS */
+#define PTHREAD_DESTRUCTOR_ITERATIONS 4
+/* >= _POSIX_THREAD_KEYS_MAX */
+#define PTHREAD_KEYS_MAX 128
+/* bionic has no specific limit */
+#undef PTHREAD_THREADS_MAX
 
 #endif