On Mon, Aug 15, 2011 at 11:25:30AM +0200, Olaf Hering wrote:
> Add new xs_reset_watches function to shutdown watches from old kernel after
> kexec boot. The old kernel does not unregister all watches in the
> shutdown path. They are still active, the double registration can not
> be detected by the new kernel. When the watches fire, unexpected events
> will arrive and the xenwatch thread will crash (jumps to NULL). An
> orderly reboot of a hvm guest will destroy the entire guest with all its
> resources (including the watches) before it is rebuilt from scratch, so
> the missing unregister is not an issue in that case.
So this patch replaces the big patch series you sent some while ago?
[I've one of your patches in my tree, but I wasn't sure about the other
ones]
>
> With this change the xenstored is instructed to wipe all active watches
> for the guest. However, a patch for xenstored is required so that it
> accepts the XS_RESET_WATCHES request from a guest.
Ok, make sure to note the c/s when that is accepted.
>
> v3:
> - use XS_RESET_WATCHES instead of XS_INTRODUCE
>
> v2:
> - move all code which deals with XS_INTRODUCE into xs_introduce()
> (based on feedback from Ian Campbell)
> - remove casts from kvec assignment
>
> Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>
>
> ---
> drivers/xen/xenbus/xenbus_xs.c | 20 ++++++++++++++++++++
> include/xen/interface/io/xs_wire.h | 6 +++++-
> 2 files changed, 25 insertions(+), 1 deletion(-)
>
> Index: linux-3.0/drivers/xen/xenbus/xenbus_xs.c
> ===================================================================
> --- linux-3.0.orig/drivers/xen/xenbus/xenbus_xs.c
> +++ linux-3.0/drivers/xen/xenbus/xenbus_xs.c
> @@ -620,6 +620,22 @@ static struct xenbus_watch *find_watch(c
> return NULL;
> }
>
> +static void xs_reset_watches(void)
> +{
> + /* dummy, empty iov not handled by xenstored */
> + struct kvec iov[1];
> + int err;
> +
> +
> + iov[0].iov_base = "dummy";
> + iov[0].iov_len = strlen(iov[0].iov_base) + 1;
> +
> + err = xs_error(xs_talkv(XBT_NIL, XS_RESET_WATCHES, iov,
> + ARRAY_SIZE(iov), NULL));
> + if (err)
> + printk(KERN_WARNING "xs_reset_watches failed: %d\n", err);
If the xenstore does not have the patch for this, what is the
error code? Is it ENOSYS? If we get that can we not print this message?
Or perhaps print:
"Yikes! We can't reset the watches. Potential crash immienient"
or something similar.
> +}
> +
> /* Register callback to watch this node. */
> int register_xenbus_watch(struct xenbus_watch *watch)
> {
> @@ -897,5 +913,9 @@ int xs_init(void)
> if (IS_ERR(task))
> return PTR_ERR(task);
>
> + /* shutdown watches for kexec boot */
> + if (xen_hvm_domain())
> + xs_reset_watches();
> +
> return 0;
> }
> Index: linux-3.0/include/xen/interface/io/xs_wire.h
> ===================================================================
> --- linux-3.0.orig/include/xen/interface/io/xs_wire.h
> +++ linux-3.0/include/xen/interface/io/xs_wire.h
> @@ -26,7 +26,11 @@ enum xsd_sockmsg_type
> XS_SET_PERMS,
> XS_WATCH_EVENT,
> XS_ERROR,
> - XS_IS_DOMAIN_INTRODUCED
> + XS_IS_DOMAIN_INTRODUCED,
> + XS_RESUME,
> + XS_SET_TARGET,
> + XS_RESTRICT,
> + XS_RESET_WATCHES
> };
>
> #define XS_WRITE_NONE "NONE"
>
> _______________________________________________
> Xen-devel mailing list
> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel
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