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authorPaolo Bonzini <pbonzini@redhat.com>2015-07-24 13:42:55 +0200
committerPeter Maydell <peter.maydell@linaro.org>2015-07-27 17:12:19 +0100
commitedec47cfef96209987cb7922286cb384916aae02 (patch)
tree72ba93a5e646a5b83526ecda1c5b16006c10c9b1 /main-loop.c
parent3737129917c918767cdb8acd8ca6b342c45fa154 (diff)
downloadqemu-arm-edec47cfef96209987cb7922286cb384916aae02.tar.gz
main-loop: fix qemu_notify_event for aio_notify optimization
aio_notify can be optimized away, and in fact almost always will. However, qemu_notify_event is used in places where this is incorrect---most notably, when handling SIGTERM. When aio_notify is optimized away, it is possible that QEMU enters a blocking ppoll immediately afterwards and stays there, without reaching main_loop_should_exit(). Fix this by using a bottom half. The bottom half can be optimized too, but scheduling it is enough for the ppoll not to block. The hang is thus avoided. Reported-by: Peter Maydell <peter.maydell@linaro.org> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 1437738175-23624-1-git-send-email-pbonzini@redhat.com Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Diffstat (limited to 'main-loop.c')
-rw-r--r--main-loop.c11
1 files changed, 10 insertions, 1 deletions
diff --git a/main-loop.c b/main-loop.c
index 82875a4dfd..39970437f8 100644
--- a/main-loop.c
+++ b/main-loop.c
@@ -114,6 +114,14 @@ static int qemu_signal_init(void)
#endif
static AioContext *qemu_aio_context;
+static QEMUBH *qemu_notify_bh;
+
+static void notify_event_cb(void *opaque)
+{
+ /* No need to do anything; this bottom half is only used to
+ * kick the kernel out of ppoll/poll/WaitForMultipleObjects.
+ */
+}
AioContext *qemu_get_aio_context(void)
{
@@ -125,7 +133,7 @@ void qemu_notify_event(void)
if (!qemu_aio_context) {
return;
}
- aio_notify(qemu_aio_context);
+ qemu_bh_schedule(qemu_notify_bh);
}
static GArray *gpollfds;
@@ -144,6 +152,7 @@ int qemu_init_main_loop(Error **errp)
}
qemu_aio_context = aio_context_new(&local_error);
+ qemu_notify_bh = qemu_bh_new(notify_event_cb, NULL);
if (!qemu_aio_context) {
error_propagate(errp, local_error);
return -EMFILE;