Re: [PATCH 5/6] test-coroutine: add rwlock upgrade test

[David Edmondson <david.edmondson@oracle.com>]

On Wednesday, 2021-03-17 at 19:00:12 +01, Paolo Bonzini wrote:

> Test that rwlock upgrade is fair, and readers go back to sleep if a writer
> is in line.
>
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Reviewed-by: David Edmondson <david.edmondson@oracle.com>

> ---
>  tests/unit/test-coroutine.c | 62 +++++++++++++++++++++++++++++++++++++
>  1 file changed, 62 insertions(+)
>
> diff --git a/tests/unit/test-coroutine.c b/tests/unit/test-coroutine.c
> index e946d93a65..6e6f51d480 100644
> --- a/tests/unit/test-coroutine.c
> +++ b/tests/unit/test-coroutine.c
> @@ -264,6 +264,67 @@ static void test_co_mutex_lockable(void)
>      g_assert(QEMU_MAKE_LOCKABLE(null_pointer) == NULL);
>  }
>  
> +static CoRwlock rwlock;
> +
> +/* Test that readers are properly sent back to the queue when upgrading,
> + * even if they are the sole readers.  The test scenario is as follows:
> + *
> + *
> + * | c1           | c2         |
> + * |--------------+------------+
> + * | rdlock       |            |
> + * | yield        |            |
> + * |              | wrlock     |
> + * |              | <queued>   |
> + * | upgrade      |            |
> + * | <queued>     | <dequeued> |
> + * |              | unlock     |
> + * | <dequeued>   |            |
> + * | unlock       |            |
> + */
> +
> +static void coroutine_fn rwlock_yield_upgrade(void *opaque)
> +{
> +    qemu_co_rwlock_rdlock(&rwlock);
> +    qemu_coroutine_yield();
> +
> +    qemu_co_rwlock_upgrade(&rwlock);
> +    qemu_co_rwlock_unlock(&rwlock);
> +
> +    *(bool *)opaque = true;
> +}
> +
> +static void coroutine_fn rwlock_wrlock_yield(void *opaque)
> +{
> +    qemu_co_rwlock_wrlock(&rwlock);
> +    qemu_coroutine_yield();
> +
> +    qemu_co_rwlock_unlock(&rwlock);
> +    *(bool *)opaque = true;
> +}
> +
> +static void test_co_rwlock_upgrade(void)
> +{
> +    bool c1_done = false;
> +    bool c2_done = false;
> +    Coroutine *c1, *c2;
> +
> +    qemu_co_rwlock_init(&rwlock);
> +    c1 = qemu_coroutine_create(rwlock_yield_upgrade, &c1_done);
> +    c2 = qemu_coroutine_create(rwlock_wrlock_yield, &c2_done);
> +
> +    qemu_coroutine_enter(c1);
> +    qemu_coroutine_enter(c2);
> +
> +    /* c1 now should go to sleep.  */
> +    qemu_coroutine_enter(c1);
> +    g_assert(!c1_done);
> +
> +    qemu_coroutine_enter(c2);
> +    g_assert(c1_done);
> +    g_assert(c2_done);
> +}
> +
>  /*
>   * Check that creation, enter, and return work
>   */
> @@ -501,6 +562,7 @@ int main(int argc, char **argv)
>      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);
> +    g_test_add_func("/locking/co-rwlock/upgrade", test_co_rwlock_upgrade);
>      if (g_test_perf()) {
>          g_test_add_func("/perf/lifecycle", perf_lifecycle);
>          g_test_add_func("/perf/nesting", perf_nesting);
> -- 
> 2.29.2

dme.
-- 
Don't you know you're never going to get to France.