[PATCH v3 7/8] memory: Assert on no ongoing memory transaction before release BQL

[Peter Xu]

Firstly, add a "prepare" function before unlocking BQL.  There're only three
places that can release the BQL: unlock(), cond_wait() or cond_timedwait().

Make sure we don't have any more ongoing memory transaction when releasing the
BQL.  This will trigger an abort if we misuse the QEMU memory model, e.g., when
calling run_on_cpu() during a memory commit.

Reviewed-by: David Hildenbrand <da...@redhat.com>
Signed-off-by: Peter Xu <pet...@redhat.com>
---
 include/exec/memory-internal.h | 1 +
 softmmu/cpus.c                 | 9 +++++++++
 softmmu/memory.c               | 6 ++++++
 3 files changed, 16 insertions(+)

diff --git a/include/exec/memory-internal.h b/include/exec/memory-internal.h
index 9fcc2af25c..3124b91c4b 100644
--- a/include/exec/memory-internal.h
+++ b/include/exec/memory-internal.h
@@ -35,6 +35,7 @@ static inline AddressSpaceDispatch 
*address_space_to_dispatch(AddressSpace *as)
 
 FlatView *address_space_get_flatview(AddressSpace *as);
 void flatview_unref(FlatView *view);
+bool memory_region_has_pending_transaction(void);
 
 extern const MemoryRegionOps unassigned_mem_ops;
 
diff --git a/softmmu/cpus.c b/softmmu/cpus.c
index 9154cd7e78..4d190f9076 100644
--- a/softmmu/cpus.c
+++ b/softmmu/cpus.c
@@ -31,6 +31,7 @@
 #include "qapi/qapi-events-run-state.h"
 #include "qapi/qmp/qerror.h"
 #include "exec/gdbstub.h"
+#include "exec/memory-internal.h"
 #include "sysemu/hw_accel.h"
 #include "exec/exec-all.h"
 #include "qemu/thread.h"
@@ -66,6 +67,11 @@
 
 static QemuMutex qemu_global_mutex;
 
+static void qemu_mutex_unlock_iothread_prepare(void)
+{
+    assert(!memory_region_has_pending_transaction());
+}
+
 bool cpu_is_stopped(CPUState *cpu)
 {
     return cpu->stopped || !runstate_is_running();
@@ -520,16 +526,19 @@ void qemu_mutex_unlock_iothread(void)
 {
     g_assert(qemu_mutex_iothread_locked());
     iothread_locked = false;
+    qemu_mutex_unlock_iothread_prepare();
     qemu_mutex_unlock(&qemu_global_mutex);
 }
 
 void qemu_cond_wait_iothread(QemuCond *cond)
 {
+    qemu_mutex_unlock_iothread_prepare();
     qemu_cond_wait(cond, &qemu_global_mutex);
 }
 
 void qemu_cond_timedwait_iothread(QemuCond *cond, int ms)
 {
+    qemu_mutex_unlock_iothread_prepare();
     qemu_cond_timedwait(cond, &qemu_global_mutex, ms);
 }
 
diff --git a/softmmu/memory.c b/softmmu/memory.c
index 35b2568fc2..62ec00b52d 100644
--- a/softmmu/memory.c
+++ b/softmmu/memory.c
@@ -176,6 +176,12 @@ static bool memory_region_has_pending_update(void)
     return memory_region_update_pending || ioeventfd_update_pending;
 }
 
+bool memory_region_has_pending_transaction(void)
+{
+    return memory_region_transaction_depth ||
+        memory_region_has_pending_update();
+}
+
 static bool memory_region_ioeventfd_before(MemoryRegionIoeventfd *a,
                                            MemoryRegionIoeventfd *b)
 {
-- 
2.31.1