[CRIU] [PATCH] pstree: Aligned pstree item allocation

[Andrei Vagin]

On Tue, Jan 31, 2017 at 11:58:13AM +0300, Kirill Tkhai wrote:
> On 30.01.2017 23:45, Andrei Vagin wrote:
> > On Sat, Jan 28, 2017 at 06:56:21PM +0300, Kirill Tkhai wrote:
> >> According to man futex(2):
> >>
> >>     "On all platforms, futexes are four-byte integers
> >>      that must be aligned on a four-byte boundary".
> >>
> >> So, allocate them aligned.
> > 
> > Why is it not aligned without this patch?
> 
> This patch points that in clear way!

The C Standard guarantees that all fields in structures aligned, doesn't
it? I don't have objections about this patch, just to know that I don't
skip something.

> 
> >>
> >> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
> >> ---
> >>  criu/include/pstree.h |    9 +++++----
> >>  criu/pstree.c         |    1 +
> >>  2 files changed, 6 insertions(+), 4 deletions(-)
> >>
> >> diff --git a/criu/include/pstree.h b/criu/include/pstree.h
> >> index b4dc6b635..ee46a14db 100644
> >> --- a/criu/include/pstree.h
> >> +++ b/criu/include/pstree.h
> >> @@ -12,6 +12,11 @@
> >>   */
> >>  #define INIT_PID	(1)
> >>  struct pstree_item {
> >> +	union {
> >> +		/* Must be 4 bytes aligned */
> >> +		futex_t		task_st;
> >> +		unsigned long	task_st_le_bits;
> >> +	};
> >>  	struct pstree_item	*parent;
> >>  	struct list_head	children;	/* list of my children */
> >>  	struct list_head	sibling;	/* linkage in my parent's children list */
> >> @@ -25,10 +30,6 @@ struct pstree_item {
> >>  	struct pid		*threads;	/* array of threads */
> >>  	CoreEntry		**core;
> >>  	TaskKobjIdsEntry	*ids;
> >> -	union {
> >> -		futex_t		task_st;
> >> -		unsigned long	task_st_le_bits;
> >> -	};
> >>  };
> >>  
> >>  enum {
> >> diff --git a/criu/pstree.c b/criu/pstree.c
> >> index 8eeea947c..bee9c8917 100644
> >> --- a/criu/pstree.c
> >> +++ b/criu/pstree.c
> >> @@ -203,6 +203,7 @@ struct pstree_item *__alloc_pstree_item(bool rst)
> >>  			return NULL;
> >>  	} else {
> >>  		sz = sizeof(*item) + sizeof(struct rst_info);
> >> +		/* Guarantees sizeof(void *) alignment */
> >>  		item = shmalloc(sz);
> >>  		if (!item)
> >>  			return NULL;
> >>
> >> _______________________________________________
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> >> https://lists.openvz.org/mailman/listinfo/criu