summaryrefslogtreecommitdiffstats
path: root/qemu/docs/aio_notify_bug.promela
diff options
context:
space:
mode:
authorYang Zhang <yang.z.zhang@intel.com>2015-08-28 09:58:54 +0800
committerYang Zhang <yang.z.zhang@intel.com>2015-09-01 12:44:00 +0800
commite44e3482bdb4d0ebde2d8b41830ac2cdb07948fb (patch)
tree66b09f592c55df2878107a468a91d21506104d3f /qemu/docs/aio_notify_bug.promela
parent9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 (diff)
Add qemu 2.4.0
Change-Id: Ic99cbad4b61f8b127b7dc74d04576c0bcbaaf4f5 Signed-off-by: Yang Zhang <yang.z.zhang@intel.com>
Diffstat (limited to 'qemu/docs/aio_notify_bug.promela')
-rw-r--r--qemu/docs/aio_notify_bug.promela140
1 files changed, 140 insertions, 0 deletions
diff --git a/qemu/docs/aio_notify_bug.promela b/qemu/docs/aio_notify_bug.promela
new file mode 100644
index 000000000..b3bfca1ca
--- /dev/null
+++ b/qemu/docs/aio_notify_bug.promela
@@ -0,0 +1,140 @@
+/*
+ * This model describes a bug in aio_notify. If ctx->notifier is
+ * cleared too late, a wakeup could be lost.
+ *
+ * Author: Paolo Bonzini <pbonzini@redhat.com>
+ *
+ * This file is in the public domain. If you really want a license,
+ * the WTFPL will do.
+ *
+ * To verify the buggy version:
+ * spin -a -DBUG docs/aio_notify_bug.promela
+ * gcc -O2 pan.c
+ * ./a.out -a -f
+ *
+ * To verify the fixed version:
+ * spin -a docs/aio_notify_bug.promela
+ * gcc -O2 pan.c
+ * ./a.out -a -f
+ *
+ * Add -DCHECK_REQ to test an alternative invariant and the
+ * "notify_me" optimization.
+ */
+
+int notify_me;
+bool event;
+bool req;
+bool notifier_done;
+
+#ifdef CHECK_REQ
+#define USE_NOTIFY_ME 1
+#else
+#define USE_NOTIFY_ME 0
+#endif
+
+active proctype notifier()
+{
+ do
+ :: true -> {
+ req = 1;
+ if
+ :: !USE_NOTIFY_ME || notify_me -> event = 1;
+ :: else -> skip;
+ fi
+ }
+ :: true -> break;
+ od;
+ notifier_done = 1;
+}
+
+#ifdef BUG
+#define AIO_POLL \
+ notify_me++; \
+ if \
+ :: !req -> { \
+ if \
+ :: event -> skip; \
+ fi; \
+ } \
+ :: else -> skip; \
+ fi; \
+ notify_me--; \
+ \
+ req = 0; \
+ event = 0;
+#else
+#define AIO_POLL \
+ notify_me++; \
+ if \
+ :: !req -> { \
+ if \
+ :: event -> skip; \
+ fi; \
+ } \
+ :: else -> skip; \
+ fi; \
+ notify_me--; \
+ \
+ event = 0; \
+ req = 0;
+#endif
+
+active proctype waiter()
+{
+ do
+ :: true -> AIO_POLL;
+ od;
+}
+
+/* Same as waiter(), but disappears after a while. */
+active proctype temporary_waiter()
+{
+ do
+ :: true -> AIO_POLL;
+ :: true -> break;
+ od;
+}
+
+#ifdef CHECK_REQ
+never {
+ do
+ :: req -> goto accept_if_req_not_eventually_false;
+ :: true -> skip;
+ od;
+
+accept_if_req_not_eventually_false:
+ if
+ :: req -> goto accept_if_req_not_eventually_false;
+ fi;
+ assert(0);
+}
+
+#else
+/* There must be infinitely many transitions of event as long
+ * as the notifier does not exit.
+ *
+ * If event stayed always true, the waiters would be busy looping.
+ * If event stayed always false, the waiters would be sleeping
+ * forever.
+ */
+never {
+ do
+ :: !event -> goto accept_if_event_not_eventually_true;
+ :: event -> goto accept_if_event_not_eventually_false;
+ :: true -> skip;
+ od;
+
+accept_if_event_not_eventually_true:
+ if
+ :: !event && notifier_done -> do :: true -> skip; od;
+ :: !event && !notifier_done -> goto accept_if_event_not_eventually_true;
+ fi;
+ assert(0);
+
+accept_if_event_not_eventually_false:
+ if
+ :: event -> goto accept_if_event_not_eventually_false;
+ fi;
+ assert(0);
+}
+#endif