[PULL 16/46] event_notifier: handle initialization failure better

[Paolo Bonzini <pbonzini@redhat.com>]

From: Maxim Levitsky <mlevitsk@redhat.com>

Add 'initialized' field and use it to avoid touching event notifiers which are
either not initialized or if their initialization failed.

This is somewhat a hack, but it seems the less intrusive way to make
virtio code deal with event notifiers that failed initialization.

Signed-off-by: Maxim Levitsky <mlevitsk@redhat.com>
Message-Id: <20201217150040.906961-4-mlevitsk@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
---
 include/qemu/event_notifier.h |  1 +
 util/event_notifier-posix.c   | 16 ++++++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/include/qemu/event_notifier.h b/include/qemu/event_notifier.h
index 3380b662f3..b79add035d 100644
--- a/include/qemu/event_notifier.h
+++ b/include/qemu/event_notifier.h
@@ -24,6 +24,7 @@ struct EventNotifier {
 #else
     int rfd;
     int wfd;
+    bool initialized;
 #endif
 };
 
diff --git a/util/event_notifier-posix.c b/util/event_notifier-posix.c
index 00d93204f9..5b2110e861 100644
--- a/util/event_notifier-posix.c
+++ b/util/event_notifier-posix.c
@@ -29,6 +29,7 @@ void event_notifier_init_fd(EventNotifier *e, int fd)
 {
     e->rfd = fd;
     e->wfd = fd;
+    e->initialized = true;
 }
 #endif
 
@@ -68,6 +69,7 @@ int event_notifier_init(EventNotifier *e, int active)
     if (active) {
         event_notifier_set(e);
     }
+    e->initialized = true;
     return 0;
 
 fail:
@@ -78,12 +80,18 @@ fail:
 
 void event_notifier_cleanup(EventNotifier *e)
 {
+    if (!e->initialized) {
+        return;
+    }
+
     if (e->rfd != e->wfd) {
         close(e->rfd);
     }
+
     e->rfd = -1;
     close(e->wfd);
     e->wfd = -1;
+    e->initialized = false;
 }
 
 int event_notifier_get_fd(const EventNotifier *e)
@@ -96,6 +104,10 @@ int event_notifier_set(EventNotifier *e)
     static const uint64_t value = 1;
     ssize_t ret;
 
+    if (!e->initialized) {
+        return -1;
+    }
+
     do {
         ret = write(e->wfd, &value, sizeof(value));
     } while (ret < 0 && errno == EINTR);
@@ -113,6 +125,10 @@ int event_notifier_test_and_clear(EventNotifier *e)
     ssize_t len;
     char buffer[512];
 
+    if (!e->initialized) {
+        return 0;
+    }
+
     /* Drain the notify pipe.  For eventfd, only 8 bytes will be read.  */
     value = 0;
     do {
-- 
2.29.2