From aa5f58ce897e5eba7e655fb62e6caa002a42215a Mon Sep 17 00:00:00 2001
From: Jan Maria Matejka <mq@ucw.cz>
Date: Mon, 10 Sep 2018 15:11:55 +0200
Subject: [PATCH] Autoconf: check whether pthread spinlock is implemented

This check is needed to build with pthreads on Android
---
 aclocal.m4   | 26 ++++++++++++++++++++++++--
 configure.ac |  8 +++++++-
 2 files changed, 31 insertions(+), 3 deletions(-)

diff --git a/aclocal.m4 b/aclocal.m4
index c401d447..d70ca7cf 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -17,8 +17,6 @@ AC_DEFUN([BIRD_CHECK_PTHREADS],
 	    [
 	      pthread_t pt;
 	      pthread_create(&pt, NULL, NULL, NULL);
-	      pthread_spinlock_t lock;
-	      pthread_spin_lock(&lock);
 	    ]
 	  )
 	],
@@ -31,6 +29,30 @@ AC_DEFUN([BIRD_CHECK_PTHREADS],
   CFLAGS="$bird_tmp_cflags"
 ])
 
+dnl ** Android API before version 24 doesn't implement spinlocks.
+AC_DEFUN([BIRD_CHECK_PTHREAD_SPINLOCK],
+[
+  AC_CACHE_CHECK(
+    [whether POSIX threads provide spinlocks],
+    [bird_cv_lib_pthread_spinlock],
+    [
+      AC_LINK_IFELSE(
+	[
+	  AC_LANG_PROGRAM(
+	    [ #include <pthread.h> ],
+	    [
+	      pthread_spinlock_t lock;
+	      pthread_spin_lock(&lock);
+	    ]
+	  )
+	],
+	[bird_cv_lib_pthread_spinlock=yes],
+	[bird_cv_lib_pthread_spinlock=no]
+      )
+    ]
+  )
+])
+
 AC_DEFUN([BIRD_CHECK_MPLS_KERNEL],
 [
   AC_CACHE_CHECK(
diff --git a/configure.ac b/configure.ac
index 943d3a7b..cfda4c7f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -120,7 +120,13 @@ if test "$enable_pthreads" != no ; then
     AC_DEFINE([USE_PTHREADS], [1], [Define to 1 if pthreads are enabled])
     CFLAGS="$CFLAGS -pthread"
     LDFLAGS="$LDFLAGS -pthread"
-    proto_bfd=bfd
+
+    BIRD_CHECK_PTHREAD_SPINLOCK
+    if test "$bird_cv_lib_pthread_spinlock" = yes ; then
+      AC_DEFINE([USE_PTHREAD_SPINLOCK], [1], [Define to 1 if pthreads provide spinlocks])
+      proto_bfd=bfd
+    fi
+
   elif test "$enable_pthreads" = yes ; then
     AC_MSG_ERROR([POSIX threads not available.])
   fi