aio / timers: Add prctl(PR_SET_TIMERSLACK, 1, ...) to reduce timer slack

Where supported, called prctl(PR_SET_TIMERSLACK, 1, ...) to
set one nanosecond timer slack to increase precision of timer
calls.

Signed-off-by: Alex Bligh <alex@alex.org.uk>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

1 files changed, 18 insertions, 0 deletions

diff --git a/configure b/configure
index 56594121ad..0a55c20252 100755
--- a/configure
+++ b/configure
@@ -2834,6 +2834,21 @@ if compile_prog "" "" ; then
   ppoll=yes
 fi
 
+# check for prctl(PR_SET_TIMERSLACK , ... ) support
+prctl_pr_set_timerslack=no
+cat > $TMPC << EOF
+#include <sys/prctl.h>
+
+int main(void)
+{
+    prctl(PR_SET_TIMERSLACK, 1, 0, 0, 0);
+    return 0;
+}
+EOF
+if compile_prog "" "" ; then
+  prctl_pr_set_timerslack=yes
+fi
+
 # check for epoll support
 epoll=no
 cat > $TMPC << EOF
@@ -3833,6 +3848,9 @@ fi
 if test "$ppoll" = "yes" ; then
   echo "CONFIG_PPOLL=y" >> $config_host_mak
 fi
+if test "$prctl_pr_set_timerslack" = "yes" ; then
+  echo "CONFIG_PRCTL_PR_SET_TIMERSLACK=y" >> $config_host_mak
+fi
 if test "$epoll" = "yes" ; then
   echo "CONFIG_EPOLL=y" >> $config_host_mak
 fi