* Daniel P. Berrangé (berra...@redhat.com) wrote:
> Some monitor functions, most notably, monitor_cur() rely on global
> data being initialized by 'monitor_init_globals()'. The latter is
> called relatively late in startup. If code triggers error_report()
> before monitor_init_globals() is called, QEMU will abort when
> accessing the uninitialized monitor mutex.
>
> The critical monitor global data must be initialized from a
> constructor function, to improve the guarantee that it is done
> before any possible calls to monitor_cur(). Not only that, but
> the constructor must be marked to run before the default
> constructor in case any of them trigger error reporting.
>
> Note in particular that the RCU constructor will spawn a background
> thread so we might even have non-constructor QEMU code running
> concurrently with other constructors.
>
> Signed-off-by: Daniel P. Berrangé <berra...@redhat.com>
Checked that qemu_mutex_init doesn't look like it can call
error code; so
Reviewed-by: Dr. David Alan Gilbert <d...@treblig.org>
> ---
> monitor/monitor.c | 14 +++++++++-----
> 1 file changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/monitor/monitor.c b/monitor/monitor.c
> index c5a5d30877..da54e1b1ce 100644
> --- a/monitor/monitor.c
> +++ b/monitor/monitor.c
> @@ -704,18 +704,22 @@ void monitor_cleanup(void)
> }
> }
>
> -static void monitor_qapi_event_init(void)
> +/*
> + * Initialize static vars that have no deps on external
> + * module initialization, and are required for external
> + * functions to call things like monitor_cur()
> + */
> +static void __attribute__((__constructor__(QEMU_CONSTRUCTOR_EARLY)))
> +monitor_init_static(void)
> {
> + qemu_mutex_init(&monitor_lock);
> + coroutine_mon = g_hash_table_new(NULL, NULL);
> monitor_qapi_event_state = g_hash_table_new(qapi_event_throttle_hash,
> qapi_event_throttle_equal);
> }
>
> void monitor_init_globals(void)
> {
> - monitor_qapi_event_init();
> - qemu_mutex_init(&monitor_lock);
> - coroutine_mon = g_hash_table_new(NULL, NULL);
> -
> /*
> * The dispatcher BH must run in the main loop thread, since we
> * have commands assuming that context. It would be nice to get
> --
> 2.50.1
>
--
-----Open up your eyes, open up your mind, open up your code -------
/ Dr. David Alan Gilbert | Running GNU/Linux | Happy \
\ dave @ treblig.org | | In Hex /
\ _________________________|_____ http://www.treblig.org |_______/
