[Qemu-devel] [PATCH] vl.c: make default main_loop_wait() timeout independed of slirp

[Igor Mammedov <imammedo@redhat.com>]

Since commit (047f7038f58 cli: add --preconfig option) QEMU is
stuck with indefinite timeout in os_host_main_loop_wait()
at RUN_STATE_PRECONFIG even if --preconfig option wasn't used
when it's started with -nodefaults CLI option like this:

  ./s390x-softmmu/qemu-system-s390x -nodefaults

It's caused by the fact that slirp_pollfds_fill() bails out early
and slirp_update_timeout() won't be called to update timeout
to a reasonable value (1 sec) so timeout would be left with
infinite value (0xFFFFFFFF).

Default infinite timeout though doen't make sense and reducing
it to 1 second as in slirp_update_timeout() won't affect host.
Fix issue by simplifying default timeout to the same 1sec as it
is in slirp_update_timeout() and cleanup the later. It makes
default timeout the same regardless of slirp_pollfds_fill()
exited early or not (i.e. -nodefaults won't have any effect on
main_loop_wait() anymore, which would provide more consistent
behavior between both variants of startup).

Reported-by: Lukáš Doktor <ldoktor@redhat.com>
Signed-off-by: Igor Mammedov <imammedo@redhat.com>
---
PS:
it doesn't fix issue reported by Max where
  "echo foo | $QEMU"
is also broken due to commit 047f7038f58, but there is antoher fix
on the list to fix that (either Michal's or Daniel's).
---
 slirp/slirp.c    | 10 ++--------
 util/main-loop.c | 13 ++-----------
 2 files changed, 4 insertions(+), 19 deletions(-)

diff --git a/slirp/slirp.c b/slirp/slirp.c
index 1cb6b07..1112f86 100644
--- a/slirp/slirp.c
+++ b/slirp/slirp.c
@@ -358,13 +358,8 @@ void slirp_cleanup(Slirp *slirp)
 static void slirp_update_timeout(uint32_t *timeout)
 {
     Slirp *slirp;
-    uint32_t t;
 
-    if (*timeout <= TIMEOUT_FAST) {
-        return;
-    }
-
-    t = MIN(1000, *timeout);
+    assert(*timeout > TIMEOUT_FAST);
 
     /* If we have tcp timeout with slirp, then we will fill @timeout with
      * more precise value.
@@ -375,10 +370,9 @@ static void slirp_update_timeout(uint32_t *timeout)
             return;
         }
         if (slirp->do_slowtimo) {
-            t = MIN(TIMEOUT_SLOW, t);
+            *timeout = MIN(TIMEOUT_SLOW, *timeout);
         }
     }
-    *timeout = t;
 }
 
 void slirp_pollfds_fill(GArray *pollfds, uint32_t *timeout)
diff --git a/util/main-loop.c b/util/main-loop.c
index 992f9b0..fd23166 100644
--- a/util/main-loop.c
+++ b/util/main-loop.c
@@ -497,25 +497,16 @@ static int os_host_main_loop_wait(int64_t timeout)
 void main_loop_wait(int nonblocking)
 {
     int ret;
-    uint32_t timeout = UINT32_MAX;
     int64_t timeout_ns;
+    uint32_t timeout = nonblocking ? 0 : 1000 /* milliseconds */;
 
-    if (nonblocking) {
-        timeout = 0;
-    }
 
     /* poll any events */
     g_array_set_size(gpollfds, 0); /* reset for new iteration */
     /* XXX: separate device handlers from system ones */
     slirp_pollfds_fill(gpollfds, &timeout);
 
-    if (timeout == UINT32_MAX) {
-        timeout_ns = -1;
-    } else {
-        timeout_ns = (uint64_t)timeout * (int64_t)(SCALE_MS);
-    }
-
-    timeout_ns = qemu_soonest_timeout(timeout_ns,
+    timeout_ns = qemu_soonest_timeout((uint64_t)timeout * (int64_t)(SCALE_MS),
                                       timerlistgroup_deadline_ns(
                                           &main_loop_tlg));
 
-- 
2.7.4