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

[Juergen Gross <jgross@xxxxxxxx>]

On 20.04.26 23:30, Jason Andryuk wrote:
> 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?
That wasn't on purpose.

Seems to be an artifact of creating the new xs_watch_helper() function.

I'll fix that and send a V2.

> Everything else looks okay.
Thanks,


Juergen

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