Make compatfd fallback more robust

Be more friendly when signalfd() fails, and also add configure checks to detect
that syscall(SYS_signalfd) actually works.  malc pointed out that some installs
do not have /usr/include/linux headers that are in sync with the glibc headers
so why SYS_signalfd is defined, it's #defined to _NR_signalfd which is not
defined in the /usr/include/linux header.

While this is a distro bug, it doesn't hurt to do a more thorough job in
detection.

Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>



git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@5334 c046a42c-6fe2-441c-8c8c-71466251a162

block-raw-posix.c

@@ -584,6 +584,10 @@ static int posix_aio_init(void)
     
     s->first_aio = NULL;
     s->fd = qemu_signalfd(&mask);
+    if (s->fd == -1) {
+        fprintf(stderr, "failed to create signalfd\n");
+        return -errno;
+    }
 
     fcntl(s->fd, F_SETFL, O_NONBLOCK);
 

compatfd.c

@@ -100,11 +100,11 @@ static int qemu_signalfd_compat(const sigset_t *mask)
 
 int qemu_signalfd(const sigset_t *mask)
 {
-#if defined(SYS_signalfd)
+#if defined(CONFIG_signalfd)
     int ret;
 
     ret = syscall(SYS_signalfd, -1, mask, _NSIG / 8);
-    if (!(ret == -1 && errno == ENOSYS))
+    if (ret != -1)
         return ret;
 #endif
 
@@ -113,15 +113,14 @@ int qemu_signalfd(const sigset_t *mask)
 
 int qemu_eventfd(int *fds)
 {
-#if defined(SYS_eventfd)
+#if defined(CONFIG_eventfd)
     int ret;
 
     ret = syscall(SYS_eventfd, 0);
     if (ret >= 0) {
         fds[0] = fds[1] = ret;
         return 0;
-    } else if (!(ret == -1 && errno == ENOSYS))
-        return ret;
+    }
 #endif
 
     return pipe(fds);

configure

@@ -110,6 +110,8 @@ curses="yes"
 aio="yes"
 nptl="yes"
 mixemu="no"
+signalfd="no"
+eventfd="no"
 
 # OS specific
 targetos=`uname -s`
@@ -901,6 +903,33 @@ EOF
   fi
 fi
 
+##########################################
+# signalfd probe
+cat > $TMPC << EOF
+#define _GNU_SOURCE
+#include <unistd.h>
+#include <sys/syscall.h>
+#include <signal.h>
+int main(void) { return syscall(SYS_signalfd, -1, NULL, _NSIG / 8); }
+EOF
+
+if $cc $ARCH_CFLAGS -o $TMPE $TMPC 2> /dev/null ; then
+  signalfd=yes
+fi
+
+##########################################
+# eventfd probe
+cat > $TMPC << EOF
+#define _GNU_SOURCE
+#include <unistd.h>
+#include <sys/syscall.h>
+int main(void) { return syscall(SYS_eventfd, 0); }
+EOF
+
+if $cc $ARCH_CFLAGS -o $TMPE $TMPC 2> /dev/null ; then
+  eventfd=yes
+fi
+
 # Check if tools are available to build documentation.
 if [ -x "`which texi2html 2>/dev/null`" ] && \
    [ -x "`which pod2man 2>/dev/null`" ]; then
@@ -1229,6 +1258,12 @@ if test "$aio" = "yes" ; then
   echo "#define CONFIG_AIO 1" >> $config_h
   echo "CONFIG_AIO=yes" >> $config_mak
 fi
+if test "$signalfd" = "yes" ; then
+  echo "#define CONFIG_signalfd 1" >> $config_h
+fi
+if test "$eventfd" = "yes" ; then
+  echo "#define CONFIG_eventfd 1" >> $config_h
+fi
 
 # XXX: suppress that
 if [ "$bsd" = "yes" ] ; then