Re: [PATCH 01/17] replay: Fix migration use of clock for statistics

[Peter Xu]

On Fri, Dec 20, 2024 at 08:42:03PM +1000, Nicholas Piggin wrote:
> Migration reads CLOCK_HOST when not holding the replay_mutex, which
> asserts when recording a trace. These are not guest visible so should
> be CLOCK_REALTIME like other statistics in MigrationState, which do
> not require the replay_mutex.

Irrelevant of the change, should we document such lock implications in
timer.h?

> 
> Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
> ---
>  migration/migration.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/migration/migration.c b/migration/migration.c
> index 8c5bd0a75c8..2eb9e50a263 100644
> --- a/migration/migration.c
> +++ b/migration/migration.c
> @@ -3433,7 +3433,7 @@ static void *migration_thread(void *opaque)
>  {
>      MigrationState *s = opaque;
>      MigrationThread *thread = NULL;
> -    int64_t setup_start = qemu_clock_get_ms(QEMU_CLOCK_HOST);
> +    int64_t setup_start = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
>      MigThrError thr_error;
>      bool urgent = false;
>      Error *local_err = NULL;
> @@ -3504,7 +3504,7 @@ static void *migration_thread(void *opaque)
>          goto out;
>      }
>  
> -    s->setup_time = qemu_clock_get_ms(QEMU_CLOCK_HOST) - setup_start;
> +    s->setup_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) - setup_start;
>  
>      trace_migration_thread_setup_complete();
>  
> @@ -3584,7 +3584,7 @@ static void *bg_migration_thread(void *opaque)
>  
>      migration_rate_set(RATE_LIMIT_DISABLED);
>  
> -    setup_start = qemu_clock_get_ms(QEMU_CLOCK_HOST);
> +    setup_start = qemu_clock_get_ms(QEMU_CLOCK_REALTIME);
>      /*
>       * We want to save vmstate for the moment when migration has been
>       * initiated but also we want to save RAM content while VM is running.
> @@ -3629,7 +3629,7 @@ static void *bg_migration_thread(void *opaque)
>          goto fail_setup;
>      }
>  
> -    s->setup_time = qemu_clock_get_ms(QEMU_CLOCK_HOST) - setup_start;
> +    s->setup_time = qemu_clock_get_ms(QEMU_CLOCK_REALTIME) - setup_start;
>  
>      trace_migration_thread_setup_complete();
>  
> -- 
> 2.45.2
> 

-- 
Peter Xu