On Sun, Nov 17, 2024 at 08:20:06PM +0100, Maciej S. Szmigiero wrote:
> From: "Maciej S. Szmigiero" <maciej.szmigiero@oracle.com>
>
> multifd_send() function is currently not thread safe, make it thread safe
> by holding a lock during its execution.
>
> This way it will be possible to safely call it concurrently from multiple
> threads.
>
> Signed-off-by: Maciej S. Szmigiero <maciej.szmigiero@oracle.com>
Reviewed-by: Peter Xu <peterx@redhat.com>
One nitpick:
> ---
> migration/multifd.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/migration/multifd.c b/migration/multifd.c
> index 9578a985449b..4575495c8816 100644
> --- a/migration/multifd.c
> +++ b/migration/multifd.c
> @@ -50,6 +50,10 @@ typedef struct {
>
> struct {
> MultiFDSendParams *params;
> +
> + /* multifd_send() body is not thread safe, needs serialization */
> + QemuMutex multifd_send_mutex;
> +
> /*
> * Global number of generated multifd packets.
> *
> @@ -331,6 +335,7 @@ static void multifd_send_kick_main(MultiFDSendParams *p)
> */
> bool multifd_send(MultiFDSendData **send_data)
> {
> + QEMU_LOCK_GUARD(&multifd_send_state->multifd_send_mutex);
Better move this after the varaible declarations to be clear..
Perhaps even after multifd_send_should_exit() because reading that doesn't
need a lock, just in case something wanna quit but keep stuck with the
mutex.
> int i;
> static int next_channel;
> MultiFDSendParams *p = NULL; /* make happy gcc */
> @@ -508,6 +513,7 @@ static void multifd_send_cleanup_state(void)
> socket_cleanup_outgoing_migration();
> qemu_sem_destroy(&multifd_send_state->channels_created);
> qemu_sem_destroy(&multifd_send_state->channels_ready);
> + qemu_mutex_destroy(&multifd_send_state->multifd_send_mutex);
> g_free(multifd_send_state->params);
> multifd_send_state->params = NULL;
> g_free(multifd_send_state);
> @@ -853,6 +859,7 @@ bool multifd_send_setup(void)
> thread_count = migrate_multifd_channels();
> multifd_send_state = g_malloc0(sizeof(*multifd_send_state));
> multifd_send_state->params = g_new0(MultiFDSendParams, thread_count);
> + qemu_mutex_init(&multifd_send_state->multifd_send_mutex);
> qemu_sem_init(&multifd_send_state->channels_created, 0);
> qemu_sem_init(&multifd_send_state->channels_ready, 0);
> qatomic_set(&multifd_send_state->exiting, 0);
>
--
Peter Xu