coroutine: implement coroutines using gthread

On platforms that don't support makecontext(3) use gthread based
coroutine implementation.

Darwin has makecontext(3) but getcontext(3) is stubbed out to return
ENOTSUP.  Andreas Färber <andreas.faerber@web.de> debugged this and
contributed the ./configure test which solves the issue for Darwin/ppc64
(and ppc) v10.5.

[Original patch by Aneesh, made consistent with coroutine-ucontext.c and
switched to GStaticPrivate by Stefan.  Tested on Linux and OpenBSD.]

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/configure b/configure
index 77194cf..1eed0cd 100755
--- a/configure
+++ b/configure
@@ -2541,6 +2541,20 @@ EOF
 fi
 
 ##########################################
+# check if we have makecontext
+
+ucontext_coroutine=no
+if test "$darwin" != "yes"; then
+  cat > $TMPC << EOF
+#include <ucontext.h>
+int main(void) { makecontext(0, 0, 0); }
+EOF
+  if compile_prog "" "" ; then
+      ucontext_coroutine=yes
+  fi
+fi
+
+##########################################
 # End of CC checks
 # After here, no more $cc or $ld runs
 
@@ -3015,6 +3029,10 @@ if test "$rbd" = "yes" ; then
   echo "CONFIG_RBD=y" >> $config_host_mak
 fi
 
+if test "$ucontext_coroutine" = "yes" ; then
+  echo "CONFIG_UCONTEXT_COROUTINE=y" >> $config_host_mak
+fi
+
 # USB host support
 case "$usb" in
 linux)