[CRIU] [PATCH RFC 18/30] files: Implement {set, get}_fds_event()

[Pavel Emelyanov]

Need comment here.

On 11/01/2016 05:33 PM, Kirill Tkhai wrote:
> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> ---
>  criu/files.c          |   37 +++++++++++++++++++++++++++++++++++++
>  criu/include/files.h  |    3 +++
>  criu/include/lock.h   |    5 +++++
>  criu/include/pstree.h |    1 +
>  4 files changed, 46 insertions(+)
> 
> diff --git a/criu/files.c b/criu/files.c
> index 29ff9d1..97e3d49 100644
> --- a/criu/files.c
> +++ b/criu/files.c
> @@ -1634,3 +1634,40 @@ static int open_transport_socket(pid_t pid)
>  
>  	return 0;
>  }
> +
> +int set_fds_event(pid_t virt)
> +{
> +	struct pstree_item *item;
> +	int old, st;
> +
> +	item = pstree_item_by_virt(virt);
> +	BUG_ON(!item);
> +
> +	/* Wait till transport_fd is installed */
> +	futex_wait_if_cond(&item->task_st, TFD_INSTALLED, &);
> +
> +	/* Set FDS_EVENT and wake up if need */
> +	do {
> +		old = futex_get(&item->task_st);
> +		if (old & FDS_EVENT)
> +			break;
> +		st = atomic_cmpxchg(&item->task_st.raw, old, old | FDS_EVENT);
> +	} while (st != old);
> +
> +	if (!(old & FDS_EVENT))
> +		futex_wake(&item->task_st);
> +	return 0;
> +}
> +
> +int wait_fds_event(void)
> +{
> +	int old, st;
> +
> +	futex_wait_if_cond(&current->task_st, FDS_EVENT, &);
> +	do {
> +		old = futex_get(&current->task_st);
> +		st = atomic_cmpxchg(&current->task_st.raw, old, old & ~FDS_EVENT);
> +	} while (st != old);
> +
> +	return 0;
> +}
> diff --git a/criu/include/files.h b/criu/include/files.h
> index ae4a9a1..7de61d8 100644
> --- a/criu/include/files.h
> +++ b/criu/include/files.h
> @@ -192,4 +192,7 @@ extern FdinfoEntry *dup_fdinfo(FdinfoEntry *old, int fd, unsigned flags);
>  int dup_fle(struct pstree_item *task, struct fdinfo_list_entry *ple,
>  	    int fd, unsigned flags);
>  
> +int set_fds_event(pid_t virt);
> +int wait_fds_event(void);
> +
>  #endif /* __CR_FILES_H__ */
> diff --git a/criu/include/lock.h b/criu/include/lock.h
> index 0a99211..fff086a 100644
> --- a/criu/include/lock.h
> +++ b/criu/include/lock.h
> @@ -79,6 +79,11 @@ static inline void futex_set_and_wake(futex_t *f, uint32_t v)
>  	LOCK_BUG_ON(sys_futex((uint32_t *)&f->raw.counter, FUTEX_WAKE, INT_MAX, NULL, NULL, 0) < 0);
>  }
>  
> +static inline void futex_wake(futex_t *f)
> +{
> +	LOCK_BUG_ON(sys_futex((uint32_t *)&f->raw.counter, FUTEX_WAKE, INT_MAX, NULL, NULL, 0) < 0);
> +}
> +
>  /* Mark futex @f as wait abort needed and wake up all waiters */
>  static inline void futex_abort_and_wake(futex_t *f)
>  {
> diff --git a/criu/include/pstree.h b/criu/include/pstree.h
> index b3547ca..425082e 100644
> --- a/criu/include/pstree.h
> +++ b/criu/include/pstree.h
> @@ -31,6 +31,7 @@ struct pstree_item {
>  enum {
>  	TSK_ALLOCATED = 0,
>  	TFD_INSTALLED = 1 << 0,
> +	FDS_EVENT     = 1 << 1,
>  };
>  
>  struct pstree_item *current;
> 
> .
>