[Qemu-devel] [PATCH v2] qemu-timer: Check for usable fields for SIGEV_THREAD_ID

[Richard Henderson <rth@twiddle.net>]

Older glibc (RHEL 5.x, Debian 5.x) does not have the _sigev_un._tid
member in its structure definition, while the accompanying kernel
headers do define SIGEV_THREAD_ID.  We need configure to check for
both before using it.

Signed-off-by: Richard Henderson <rth@twiddle.net>
---
 configure    | 22 ++++++++++++++++++++++
 qemu-timer.c |  4 ++--
 2 files changed, 24 insertions(+), 2 deletions(-)

Version 2 avoids a warning in the test program.


r~



diff --git a/configure b/configure
index 9f33c7d..358a3aa 100755
--- a/configure
+++ b/configure
@@ -2813,6 +2813,24 @@ if compile_prog "" "" ; then
 fi
 
 ##########################################
+# check if we have usable SIGEV_THREAD_ID
+
+sigev_thread_id=no
+cat > $TMPC << EOF
+#include <signal.h>
+int main(void) {
+  struct sigevent ev;
+  ev.sigev_notify = SIGEV_THREAD_ID;
+  ev._sigev_un._tid = 0;
+  asm volatile("" : : "g"(&ev));
+  return 0;
+}
+EOF
+if compile_prog "" "" ; then
+    sigev_thread_id=yes
+fi
+
+##########################################
 # check if trace backend exists
 
 $python "$source_path/scripts/tracetool.py" "--backend=$trace_backend" --check-backend  > /dev/null 2> /dev/null
@@ -3159,6 +3177,7 @@ echo "preadv support    $preadv"
 echo "fdatasync         $fdatasync"
 echo "madvise           $madvise"
 echo "posix_madvise     $posix_madvise"
+echo "sigev_thread_id   $sigev_thread_id"
 echo "uuid support      $uuid"
 echo "libcap-ng support $cap_ng"
 echo "vhost-net support $vhost_net"
@@ -3443,6 +3462,9 @@ fi
 if test "$posix_madvise" = "yes" ; then
   echo "CONFIG_POSIX_MADVISE=y" >> $config_host_mak
 fi
+if test "$sigev_thread_id" = "yes" ; then
+  echo "CONFIG_SIGEV_THREAD_ID=y" >> $config_host_mak
+fi
 
 if test "$spice" = "yes" ; then
   echo "CONFIG_SPICE=y" >> $config_host_mak
diff --git a/qemu-timer.c b/qemu-timer.c
index 908a103..ede84ff 100644
--- a/qemu-timer.c
+++ b/qemu-timer.c
@@ -494,12 +494,12 @@ static int dynticks_start_timer(struct qemu_alarm_timer *t)
     memset(&ev, 0, sizeof(ev));
     ev.sigev_value.sival_int = 0;
     ev.sigev_notify = SIGEV_SIGNAL;
-#ifdef SIGEV_THREAD_ID
+#ifdef CONFIG_SIGEV_THREAD_ID
     if (qemu_signalfd_available()) {
         ev.sigev_notify = SIGEV_THREAD_ID;
         ev._sigev_un._tid = qemu_get_thread_id();
     }
-#endif /* SIGEV_THREAD_ID */
+#endif /* CONFIG_SIGEV_THREAD_ID */
     ev.sigev_signo = SIGALRM;
 
     if (timer_create(CLOCK_REALTIME, &ev, &host_timer)) {
-- 
1.7.11.7