Re: [PATCH 3/8] tools/libs/store: add support to use watches with a depth parameter

[Jason Andryuk <jason.andryuk@xxxxxxx>]

On 2026-03-13 03:47, Juergen Gross wrote:
> Add a new xs_watch_depth() function to libxenstore allowing to limit
> the scope of a Xenstore watch. It can be used only in case Xenstore is
> supporting the XENSTORE_SERVER_FEATURE_WATCHDEPTH feature.
>
> For convenience add a xs_watch_try_depth() wrapper, which will call
> xs_watch_depth() if supported and xs_watch() otherwise.
>
> Cache the supported features of Xenstore in order not having to get
> them from Xenstore for each call of one of the new functions.
>
> Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
> @@ -984,37 +984,29 @@ bool xs_restrict(struct xs_handle *h, unsigned domid)
>         return false;
>   }
>   
> -/* Watch a node for changes (poll on fd to detect, or call read_watch()).
> - * When the node (or any child) changes, fd will become readable.
> - * Token is returned when watch is read, to allow matching.
> - * Returns false on failure.
> - */
> -bool xs_watch(struct xs_handle *h, const char *path, const char *token)
> +static bool xs_watch_helper(struct xs_handle *h)
>   {
> -       struct xsd_sockmsg msg = { .type = XS_WATCH };
> -       struct iovec iov[3];
> -
>   #ifdef USE_PTHREAD
> +       sigset_t set, old_set;
> +       pthread_attr_t attr;
> +       static size_t stack_size;
> +#ifdef USE_DLSYM
> +       size_t (*getsz)(pthread_attr_t *attr);
> +#endif
> +
>   #define DEFAULT_THREAD_STACKSIZE (16 * 1024)
>   /* NetBSD doesn't have PTHREAD_STACK_MIN. */
>   #ifndef PTHREAD_STACK_MIN
>   # define PTHREAD_STACK_MIN 0
>   #endif
>   
> -#define READ_THREAD_STACKSIZE 					\
> -       ((DEFAULT_THREAD_STACKSIZE < PTHREAD_STACK_MIN) ?    \
> +#define READ_THREAD_STACKSIZE                                  \
> +       ((DEFAULT_THREAD_STACKSIZE < PTHREAD_STACK_MIN) ?    \
>          PTHREAD_STACK_MIN : DEFAULT_THREAD_STACKSIZE)
>   
>   	/* We dynamically create a reader thread on demand. */
>         mutex_lock(&h->request_mutex);
>         if (!h->read_thr_exists) {
> -               sigset_t set, old_set;
> -               pthread_attr_t attr;
> -               static size_t stack_size;
> -#ifdef USE_DLSYM
> -               size_t (*getsz)(pthread_attr_t *attr);
> -#endif
AFAICT, there is no particular reason to change the scope of these 
variables.  Am I missing something?
Everything else looks okay.

Thanks,
Jason