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

[Andrei Vagin]

On Wed, Feb 08, 2017 at 12:51:05PM +0300, Pavel Emelyanov wrote:
> 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???

Wait all tasks except the current one. Threads are created on this stage
and each thread has to report at the end of this stage.
> 
> > +	}
> > +
> > +	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;
> > 
>