[CRIU] [PATCH] pstree: Aligned pstree item allocation
Andrei Vagin
avagin at virtuozzo.com
Mon Jan 30 12:45:33 PST 2017
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?
>
> 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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