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From: "Marek Marczykowski-Górecki" <marmarek@invisiblethingslab.com>
To: Ian Jackson <ian.jackson@citrix.com>
Cc: Simon Gaiser <simon@invisiblethingslab.com>,
	xen-devel@lists.xenproject.org,
	Anthony PERARD <anthony.perard@citrix.com>,
	Wei Liu <wei.liu2@citrix.com>, Eric Shelton <eshelton@pobox.com>
Subject: Re: [RFC PATCH v2 00/17] Add support for qemu-xen runnning in a Linux-based stubdomain.
Date: Thu, 1 Nov 2018 19:04:45 +0100	[thread overview]
Message-ID: <20181101180445.GD1638@mail-itl> (raw)
In-Reply-To: <23515.15477.194395.558778@mariner.uk.xensource.com>


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On Thu, Nov 01, 2018 at 05:48:37PM +0000, Ian Jackson wrote:
> libxl has code for waiting for xs watches and domain death and so on
> already.
> 
> How about this: provide a new variant of libxenvchan_client_init which
> can give a return indication of the form `this server does not appear
> to be set up; please watch on the following xenstore key and then call
> me again when the watch fires'.  That would be simple, and not involve
> further event loop entanglement, and would fit nicely into libxl.

Doing it in this order would be susceptible to a race condition -
server appearing after libxenvchan_client_init check, but before libxl
register the watch. Also, right now libxenvchan_client_init have only
one possible error code: NULL (instead of struct libxenvchan *). Adding
more elaborate error reporting would require API change.

As the xs path is provided by libxenvchan_client_init caller anyway,
libxl can register watch before calling libxenvchan_client_init and wait
on it if libxenvchan_client_init fails. In _this particular case_ other
conditions don't need to be handled specifically, as in the worst case it
will hit startup/qmp timeout. 

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
A: Because it messes up the order in which people normally read text.
Q: Why is top-posting such a bad thing?

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  reply	other threads:[~2018-11-01 18:04 UTC|newest]

Thread overview: 85+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-08-07  2:16 [RFC PATCH v2 00/17] Add support for qemu-xen runnning in a Linux-based stubdomain Marek Marczykowski-Górecki
2018-08-07  2:16 ` [RFC PATCH v2 01/17] libxl: fix qemu-trad cmdline for no sdl/vnc case Marek Marczykowski-Górecki
2018-08-09  9:19   ` Wei Liu
2018-10-16 16:55   ` Ian Jackson
2018-08-07  2:16 ` [RFC PATCH v2 02/17] libxl: Add "stubdomain_version" to domain_build_info Marek Marczykowski-Górecki
2018-08-09  9:25   ` Wei Liu
2018-09-03 22:25     ` Marek Marczykowski-Górecki
2018-10-16 16:43       ` Ian Jackson
2018-10-16 17:36         ` Marek Marczykowski-Górecki
2018-08-07  2:16 ` [RFC PATCH v2 03/17] libxl: Handle Linux stubdomain specific QEMU options Marek Marczykowski-Górecki
2018-08-09  9:31   ` Wei Liu
2018-08-09 16:23   ` Jason Andryuk
2018-10-16 17:16   ` Ian Jackson
2018-10-16 17:51     ` Marek Marczykowski-Górecki
2018-10-19  9:32     ` Roger Pau Monné
2018-08-07  2:16 ` [RFC PATCH v2 04/17] libxl: Build the domain with a Linux based stubdomain Marek Marczykowski-Górecki
2018-08-07  2:16 ` [RFC PATCH v2 05/17] libxl: use xenstore for pci hotplug qemu-in-linux-stubdom commands Marek Marczykowski-Górecki
2018-08-07  2:16 ` [RFC PATCH v2 06/17] libxl: create vkb device only for guests with graphics output Marek Marczykowski-Górecki
2018-11-01 17:05   ` Ian Jackson
2018-11-01 20:24     ` Stefano Stabellini
2018-08-07  2:16 ` [RFC PATCH v2 07/17] libxl: add save/restore support for qemu-xen in stubdomain Marek Marczykowski-Górecki
2018-11-01 17:11   ` Ian Jackson
2018-11-01 17:16     ` Marek Marczykowski-Górecki
2018-11-01 17:41       ` Ian Jackson
2018-08-07  2:16 ` [RFC PATCH v2 08/17] xl: add stubdomain related options to xl config parser Marek Marczykowski-Górecki
2018-08-07  2:16 ` [RFC PATCH v2 09/17] libxl: use \x1b to separate qemu arguments for linux stubdomain Marek Marczykowski-Górecki
2018-08-07  2:16 ` [RFC PATCH v2 10/17] xenconsoled: install xenstore watch for all supported consoles Marek Marczykowski-Górecki
2018-09-19 17:43   ` Wei Liu
2018-08-07  2:16 ` [RFC PATCH v2 11/17] xenconsoled: add support for consoles using 'state' xenstore entry Marek Marczykowski-Górecki
2018-11-01 17:21   ` Ian Jackson
2019-01-09 12:21     ` Marek Marczykowski-Górecki
2018-08-07  2:16 ` [RFC PATCH v2 12/17] xenconsoled: make console_type->use_gnttab less confusing Marek Marczykowski-Górecki
2018-11-01 17:25   ` Ian Jackson
2018-08-07  2:16 ` [RFC PATCH v2 13/17] xenconsoled: add support for up to 3 secondary consoles Marek Marczykowski-Górecki
2018-11-01 17:31   ` Ian Jackson
2018-11-01 18:25     ` Marek Marczykowski-Górecki
2018-11-01 20:27     ` Stefano Stabellini
2018-11-02 17:50       ` [RFC PATCH v2 13/17] xenconsoled: add support for up to 3 secondary consoles [and 1 more messages] Ian Jackson
2018-08-07  2:16 ` [RFC PATCH v2 14/17] xenconsoled: deduplicate error handling Marek Marczykowski-Górecki
2018-11-01 17:31   ` Ian Jackson
2018-08-07  2:16 ` [RFC PATCH v2 15/17] xenconsoled: add support for non-pty output Marek Marczykowski-Górecki
2018-11-01 17:35   ` Ian Jackson
2018-11-01 17:54     ` Marek Marczykowski-Górecki
2018-08-07  2:16 ` [RFC PATCH v2 16/17] libxl: access QMP socket via console for qemu-in-stubdomain Marek Marczykowski-Górecki
2018-11-01 17:38   ` Ian Jackson
2018-08-07  2:16 ` [RFC PATCH v2 17/17] libxl: use xenconsoled even for multiple stubdomain's consoles Marek Marczykowski-Górecki
2018-10-16 16:53 ` [RFC PATCH v2 00/17] Add support for qemu-xen runnning in a Linux-based stubdomain Ian Jackson
2018-10-16 17:32   ` Marek Marczykowski-Górecki
2018-10-16 17:52     ` Ian Jackson
2018-10-16 20:46       ` Marek Marczykowski-Górecki
2018-10-17 10:17         ` Ian Jackson
2018-10-17 15:16         ` Ian Jackson
2018-10-17 16:05           ` Marek Marczykowski-Górecki
2018-11-01 16:57             ` Ian Jackson
2018-11-01 17:32               ` Marek Marczykowski-Górecki
2018-11-01 17:48                 ` Ian Jackson
2018-11-01 18:04                   ` Marek Marczykowski-Górecki [this message]
2018-11-02 16:53                     ` Ian Jackson
2018-11-02 17:01                       ` [PATCH 0/8] libvchan: Minor improvements Ian Jackson
2018-11-02 17:01                         ` [PATCH 1/8] tools/libvchan: Initialise xs_transaction_t to XBT_NULL, not NULL Ian Jackson
2018-11-06  9:40                           ` Wei Liu
2018-11-02 17:01                         ` [PATCH 2/8] tools/xenstore: Document that xs_close(0) is OK Ian Jackson
2018-11-06  9:41                           ` Wei Liu
2018-11-28 11:41                             ` Wei Liu
2018-11-02 17:01                         ` [PATCH 3/8] tools/libvchan: init_xs_srv: Simplify error handling (1) Ian Jackson
2018-11-06  9:47                           ` Wei Liu
2018-11-02 17:01                         ` [PATCH 4/8] tools/libvchan: init_xs_srv: Simplify error handling (2) Ian Jackson
2018-11-06  9:48                           ` Wei Liu
2018-11-06 11:42                             ` Ian Jackson
2018-11-02 17:01                         ` [PATCH 5/8] tools/libvchan: init_xs_srv: Turn xs retry from goto into for (; ; ) Ian Jackson
2018-11-06  9:48                           ` Wei Liu
2018-11-02 17:01                         ` [PATCH 6/8] tools/libvchan: Add xentoollog to direct dependencies Ian Jackson
2018-11-06  9:48                           ` Wei Liu
2018-11-02 17:01                         ` [PATCH 7/8] tools/libvchan: libxenvchan_*_init: Promise an errno Ian Jackson
2018-11-06  9:49                           ` Wei Liu
2018-11-02 17:01                         ` [PATCH 8/8] tools/libvchan: libxenvchan_client_init: use ENOENT for no server Ian Jackson
2018-11-06 10:00                           ` Wei Liu
2018-11-06 11:45                             ` Ian Jackson
2018-11-06 12:15                               ` Marek Marczykowski-Górecki
2018-11-06 15:57                                 ` Ian Jackson
2018-11-15 17:41                 ` [RFC PATCH v2 00/17] Add support for qemu-xen runnning in a Linux-based stubdomain Anthony PERARD
2018-11-15 18:57                   ` Marek Marczykowski-Górecki
2018-11-16 10:39                     ` Anthony PERARD
2018-11-18 17:25                       ` Marek Marczykowski-Górecki
2018-11-19 12:03                         ` Anthony PERARD

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