[CRIU] [PATCH 07/11] restore: add a function to wait when other tasks finish a stage

[Pavel Emelyanov]

On 02/02/2017 03:04 AM, Andrei Vagin wrote:
> From: Andrei Vagin <avagin at virtuozzo.com>
> 
> It is used now to close descriptors of mount namespaces
> and will be used for network namespaces too.
> 
> Signed-off-by: Andrei Vagin <avagin at virtuozzo.com>
> ---
>  criu/cr-restore.c | 28 +++++++++++++++++++++++++++-
>  1 file changed, 27 insertions(+), 1 deletion(-)
> 
> diff --git a/criu/cr-restore.c b/criu/cr-restore.c
> index ba8ee57..681655d 100644
> --- a/criu/cr-restore.c
> +++ b/criu/cr-restore.c
> @@ -119,6 +119,7 @@ static int prepare_rlimits(int pid, struct task_restore_args *, CoreEntry *core)
>  static int prepare_posix_timers(int pid, struct task_restore_args *ta, CoreEntry *core);
>  static int prepare_signals(int pid, struct task_restore_args *, CoreEntry *core);
>  
> +static void restore_wait_other_tasks();
>  
>  static int crtools_prepare_shared(void)
>  {
> @@ -1474,7 +1475,7 @@ static int restore_task_with_children(void *_arg)
>  		 * Wait when all tasks passed the CR_STATE_FORKING stage.
>  		 * It means that all tasks entered into their namespaces.
>  		 */
> -		futex_wait_while_gt(&task_entries->nr_in_progress, 1);
> +		restore_wait_other_tasks();
>  
>  		fini_restore_mntns();
>  	}
> @@ -1518,6 +1519,19 @@ static inline int stage_participants(int next_stage)
>  	return -1;
>  }
>  
> +static inline int stage_current_participants(int next_stage)
> +{
> +	switch (next_stage) {
> +	case CR_STATE_FORKING:
> +		return 1;

Waiting for nr_in_progress to become 1 (or less) makes sense, but ...

> +	case CR_STATE_RESTORE:
> +		return current->nr_threads;

Why this???

> +	}
> +
> +	BUG();
> +	return -1;
> +}
> +
>  static int restore_wait_inprogress_tasks()
>  {
>  	int ret;
> @@ -1546,6 +1560,18 @@ static int restore_switch_stage(int next_stage)
>  	return restore_wait_inprogress_tasks();
>  }
>  
> +/* Wait all tasks except the current one */
> +static void restore_wait_other_tasks()
> +{
> +	int participants, stage;
> +
> +	stage = futex_get(&task_entries->start);
> +	participants = stage_current_participants(stage);
> +
> +	futex_wait_while_gt(&task_entries->nr_in_progress,
> +				participants);
> +}
> +
>  static int attach_to_tasks(bool root_seized)
>  {
>  	struct pstree_item *item;
>