lockable: add QemuLockable

QemuLockable is a polymorphic lock type that takes an object and
knows which function to use for locking and unlocking.  The
implementation could use C11 _Generic, but since the support is
not very widespread I am instead using __builtin_choose_expr and
__builtin_types_compatible_p, which are already used by
include/qemu/atomic.h.

QemuLockable can be used to implement lock guards, or to pass around
a lock in such a way that a function can release it and re-acquire it.
The next patch will do this for CoQueue.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-Id: <20180203153935.8056-3-pbonzini@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>

1 files changed, 25 insertions, 0 deletions

diff --git a/tests/test-coroutine.c b/tests/test-coroutine.c
index ab8fdf701e..28e79b3210 100644
--- a/tests/test-coroutine.c
+++ b/tests/test-coroutine.c
@@ -14,6 +14,7 @@
 #include "qemu/osdep.h"
 #include "qemu/coroutine.h"
 #include "qemu/coroutine_int.h"
+#include "qemu/lockable.h"
 
 /*
  * Check that qemu_in_coroutine() works
@@ -210,6 +211,18 @@ static void coroutine_fn mutex_fn(void *opaque)
     done++;
 }
 
+static void coroutine_fn lockable_fn(void *opaque)
+{
+    QemuLockable *x = opaque;
+    qemu_lockable_lock(x);
+    assert(!locked);
+    locked = true;
+    qemu_coroutine_yield();
+    locked = false;
+    qemu_lockable_unlock(x);
+    done++;
+}
+
 static void do_test_co_mutex(CoroutineEntry *entry, void *opaque)
 {
     Coroutine *c1 = qemu_coroutine_create(entry, opaque);
@@ -240,6 +253,17 @@ static void test_co_mutex(void)
     do_test_co_mutex(mutex_fn, &m);
 }
 
+static void test_co_mutex_lockable(void)
+{
+    CoMutex m;
+    CoMutex *null_pointer = NULL;
+
+    qemu_co_mutex_init(&m);
+    do_test_co_mutex(lockable_fn, QEMU_MAKE_LOCKABLE(&m));
+
+    g_assert(QEMU_MAKE_LOCKABLE(null_pointer) == NULL);
+}
+
 /*
  * Check that creation, enter, and return work
  */
@@ -478,6 +502,7 @@ int main(int argc, char **argv)
     g_test_add_func("/basic/in_coroutine", test_in_coroutine);
     g_test_add_func("/basic/order", test_order);
     g_test_add_func("/locking/co-mutex", test_co_mutex);
+    g_test_add_func("/locking/co-mutex/lockable", test_co_mutex_lockable);
     if (g_test_perf()) {
         g_test_add_func("/perf/lifecycle", perf_lifecycle);
         g_test_add_func("/perf/nesting", perf_nesting);