configure: Don't fall back to gthread coroutine backend

The gthread coroutine backend is broken and does not produce a working
QEMU; it is only useful for some very limited debugging situations.
Clean up the backend selection logic in configure so that it now runs
"if on windows use windows; else prefer ucontext; else sigaltstack".

To do this we refactor the configure code to separate out "test
whether we have a working ucontext", "pick a default if user didn't
specify" and "validate that user didn't specify something invalid",
rather than having all three of these run together. We also simplify
the Makefile logic so it just links in the backend the configure
script selects.

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Message-id: 1365419487-19867-3-git-send-email-peter.maydell@linaro.org
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

diff --git a/Makefile.objs b/Makefile.objs
index f99841ce5495e0b8360f73d17a2d502adeb54b04..e568c018b33fb23db709df73d7b55507cb449bdb 100644 (file)
--- a/Makefile.objs
+++ b/Makefile.objs
@@ -16,16 +16,7 @@ block-obj-y += qapi-types.o qapi-visit.o
 
 block-obj-y += qemu-coroutine.o qemu-coroutine-lock.o qemu-coroutine-io.o
 block-obj-y += qemu-coroutine-sleep.o
-ifeq ($(CONFIG_UCONTEXT_COROUTINE),y)
-block-obj-$(CONFIG_POSIX) += coroutine-ucontext.o
-else
-ifeq ($(CONFIG_SIGALTSTACK_COROUTINE),y)
-block-obj-$(CONFIG_POSIX) += coroutine-sigaltstack.o
-else
-block-obj-$(CONFIG_POSIX) += coroutine-gthread.o
-endif
-endif
-block-obj-$(CONFIG_WIN32) += coroutine-win32.o
+block-obj-y += coroutine-$(CONFIG_COROUTINE_BACKEND).o
 
 ifeq ($(CONFIG_VIRTIO)$(CONFIG_VIRTFS)$(CONFIG_PCI),yyy)
 # Lots of the fsdev/9pcode is pulled in by vl.c via qemu_fsdev_add.

diff --git a/configure b/configure
index a097fde47970b75d15ad24493fa9ecfe315c4d4e..3738de4bd60492dba59b294068a3a6e76bd075dc 100755 (executable)
--- a/configure
+++ b/configure
@@ -3071,31 +3071,58 @@ fi
 ##########################################
 # check and set a backend for coroutine
 
-# default is ucontext, but always fallback to gthread
-# windows autodetected by make
-if test "$coroutine" = "" -o "$coroutine" = "ucontext"; then
-  if test "$darwin" != "yes"; then
-    cat > $TMPC << EOF
+# We prefer ucontext, but it's not always possible. The fallback
+# is sigcontext. gthread is not selectable except explicitly, because
+# it is not functional enough to run QEMU proper. (It is occasionally
+# useful for debugging purposes.)  On Windows the only valid backend
+# is the Windows-specific one.
+
+ucontext_works=no
+if test "$darwin" != "yes"; then
+  cat > $TMPC << EOF
 #include <ucontext.h>
 #ifdef __stub_makecontext
 #error Ignoring glibc stub makecontext which will always fail
 #endif
 int main(void) { makecontext(0, 0, 0); return 0; }
 EOF
-    if compile_prog "" "" ; then
-        coroutine_backend=ucontext
-    else
-       coroutine_backend=gthread
-    fi
+  if compile_prog "" "" ; then
+    ucontext_works=yes
+  fi
+fi
+
+if test "$coroutine" = ""; then
+  if test "$mingw32" = "yes"; then
+    coroutine=win32
+  elif test "$ucontext_works" = "yes"; then
+    coroutine=ucontext
+  else
+    coroutine=sigaltstack
   fi
-elif test "$coroutine" = "gthread" ; then
-  coroutine_backend=gthread
-elif test "$coroutine" = "windows" ; then
-  coroutine_backend=windows
-elif test "$coroutine" = "sigaltstack" ; then
-  coroutine_backend=sigaltstack
 else
-  error_exit "unknown coroutine backend $coroutine"
+  case $coroutine in
+  windows)
+    if test "$mingw32" != "yes"; then
+      error_exit "'windows' coroutine backend only valid for Windows"
+    fi
+    # Unfortunately the user visible backend name doesn't match the
+    # coroutine-*.c filename for this case, so we have to adjust it here.
+    coroutine=win32
+    ;;
+  ucontext)
+    if test "$ucontext_works" != "yes"; then
+      feature_not_found "ucontext"
+    fi
+    ;;
+  gthread|sigaltstack)
+    if test "$mingw32" = "yes"; then
+      error_exit "only the 'windows' coroutine backend is valid for Windows"
+    fi
+    ;;
+  *)
+    error_exit "unknown coroutine backend $coroutine"
+    ;;
+  esac
 fi
 
 ##########################################
@@ -3402,7 +3429,7 @@ echo "GLX support       $glx"
 echo "libiscsi support  $libiscsi"
 echo "build guest agent $guest_agent"
 echo "seccomp support   $seccomp"
-echo "coroutine backend $coroutine_backend"
+echo "coroutine backend $coroutine"
 echo "GlusterFS support $glusterfs"
 echo "virtio-blk-data-plane $virtio_blk_data_plane"
 echo "gcov              $gcov_tool"
@@ -3735,11 +3762,7 @@ if test "$rbd" = "yes" ; then
   echo "CONFIG_RBD=y" >> $config_host_mak
 fi
 
-if test "$coroutine_backend" = "ucontext" ; then
-  echo "CONFIG_UCONTEXT_COROUTINE=y" >> $config_host_mak
-elif test "$coroutine_backend" = "sigaltstack" ; then
-  echo "CONFIG_SIGALTSTACK_COROUTINE=y" >> $config_host_mak
-fi
+echo "CONFIG_COROUTINE_BACKEND=$coroutine" >> $config_host_mak
 
 if test "$open_by_handle_at" = "yes" ; then
   echo "CONFIG_OPEN_BY_HANDLE=y" >> $config_host_mak

diff --git a/tests/Makefile b/tests/Makefile
index 567e36e777926b52180907835eb39c984b11c163..7fa15c6c0896e2e9a9804210f757928b2e2f7220 100644 (file)
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -24,19 +24,7 @@ gcov-files-test-string-input-visitor-y = qapi/string-input-visitor.c
 check-unit-y += tests/test-string-output-visitor$(EXESUF)
 gcov-files-test-string-output-visitor-y = qapi/string-output-visitor.c
 check-unit-y += tests/test-coroutine$(EXESUF)
-ifeq ($(CONFIG_WIN32),y)
-gcov-files-test-coroutine-y = coroutine-win32.c
-else
-ifeq ($(CONFIG_UCONTEXT_COROUTINE),y)
-gcov-files-test-coroutine-y = coroutine-ucontext.c
-else
-ifeq ($(CONFIG_SIGALTSTACK_COROUTINE),y)
-gcov-files-test-coroutine-y = coroutine-sigaltstack.c
-else
-gcov-files-test-coroutine-y = coroutine-gthread.c
-endif
-endif
-endif
+gcov-files-test-coroutine-y = coroutine-$(CONFIG_COROUTINE_BACKEND).c
 check-unit-y += tests/test-visitor-serialization$(EXESUF)
 check-unit-y += tests/test-iov$(EXESUF)
 gcov-files-test-iov-y = util/iov.c