From: Volodymyr Babchuk <Volodymyr_Babchuk@epam.com>
To: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: "xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
Andrew Cooper <andrew.cooper3@citrix.com>,
George Dunlap <george.dunlap@citrix.com>,
Jan Beulich <jbeulich@suse.com>, Julien Grall <julien@xen.org>,
Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>
Subject: Re: [PATCH v3 1/6] xen: add reference counter support
Date: Tue, 11 Apr 2023 22:27:45 +0000 [thread overview]
Message-ID: <87h6tmxden.fsf@epam.com> (raw)
In-Reply-To: <ZBMfpnzW4YdqEiA0@Air-de-Roger>
Hello Roger,
Sorry for the late answer.
Roger Pau Monné <roger.pau@citrix.com> writes:
> On Tue, Mar 14, 2023 at 08:56:29PM +0000, Volodymyr Babchuk wrote:
>> We can use reference counter to ease up object lifetime management.
>> This patch adds very basic support for reference counters. refcnt
>> should be used in the following way:
>>
>> 1. Protected structure should have refcnt_t field
>>
>> 2. This field should be initialized with refcnt_init() during object
>> construction.
>>
>> 3. If code holds a valid pointer to a structure/object it can increase
>> refcount with refcnt_get(). No additional locking is required.
>>
>> 4. Code should call refcnt_put() before dropping pointer to a
>> protected structure. `destructor` is a call back function that should
>> destruct object and free all resources, including structure protected
>> itself. Destructor will be called if reference counter reaches zero.
>>
>> 5. If code does not hold a valid pointer to a protected structure it
>> should use other locking mechanism to obtain a pointer. For example,
>> it should lock a list that hold protected objects.
>
> Sorry, I didn't look at the previous versions, but did we consider
> importing refcount_t and related logic from Linux?
Well, I considered this. But it is more complex. It has separate
refcount module, which just counts references + kref code, that is
capable of calling destructors. I am not sure if Xen need this
division. In any case, I tried to replicate Linux behavior as close as
possible. On other hand, Jan suggests to rework API, so it will be
differ from Linux one...
--
WBR, Volodymyr
next prev parent reply other threads:[~2023-04-11 22:28 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-14 20:56 [PATCH v3 0/6] vpci: first series in preparation for vpci on ARM Volodymyr Babchuk
2023-03-14 20:56 ` [PATCH v3 1/6] xen: add reference counter support Volodymyr Babchuk
2023-03-16 13:54 ` Roger Pau Monné
2023-03-16 14:03 ` Jan Beulich
2023-03-16 16:21 ` Roger Pau Monné
2023-04-11 22:27 ` Volodymyr Babchuk [this message]
2023-04-12 10:12 ` Roger Pau Monné
2023-03-16 16:19 ` Roger Pau Monné
2023-03-16 16:32 ` Jan Beulich
2023-03-16 16:39 ` Roger Pau Monné
2023-03-16 16:43 ` Jan Beulich
2023-03-16 16:48 ` Roger Pau Monné
2023-03-16 16:56 ` Jan Beulich
2023-03-17 10:05 ` Roger Pau Monné
2023-03-17 14:46 ` Jan Beulich
2023-03-16 17:01 ` Jan Beulich
2023-04-11 22:38 ` Volodymyr Babchuk
2023-04-17 6:47 ` Jan Beulich
2023-03-14 20:56 ` [PATCH v3 2/6] xen: pci: introduce reference counting for pdev Volodymyr Babchuk
2023-03-16 16:16 ` Roger Pau Monné
2023-03-29 9:55 ` Jan Beulich
2023-03-29 10:48 ` Roger Pau Monné
2023-03-29 11:58 ` Jan Beulich
2023-04-11 23:41 ` Volodymyr Babchuk
2023-04-12 9:13 ` Roger Pau Monné
2023-04-12 21:54 ` Volodymyr Babchuk
2023-04-13 15:00 ` Roger Pau Monné
2023-04-14 1:30 ` Volodymyr Babchuk
2023-04-17 10:17 ` Roger Pau Monné
2023-04-17 10:34 ` Jan Beulich
2023-04-17 10:51 ` Roger Pau Monné
2023-04-17 11:02 ` Jan Beulich
2023-04-21 11:00 ` Volodymyr Babchuk
2023-04-21 12:24 ` Jan Beulich
2023-04-21 13:02 ` Volodymyr Babchuk
2023-04-21 13:10 ` Roger Pau Monné
2023-04-21 14:13 ` Volodymyr Babchuk
2023-04-24 7:46 ` Jan Beulich
2023-04-24 14:15 ` Volodymyr Babchuk
2023-04-24 14:27 ` Jan Beulich
2023-03-29 10:04 ` Jan Beulich
2023-03-14 20:56 ` [PATCH v3 3/6] vpci: crash domain if we wasn't able to (un) map vPCI regions Volodymyr Babchuk
2023-03-16 16:32 ` Roger Pau Monné
2023-03-14 20:56 ` [PATCH v3 6/6] xen: pci: print reference counter when dumping pci_devs Volodymyr Babchuk
2023-03-17 8:46 ` Roger Pau Monné
2023-03-14 20:56 ` [PATCH v3 5/6] vpci: use reference counter to protect vpci state Volodymyr Babchuk
2023-03-17 8:43 ` Roger Pau Monné
2023-03-29 9:31 ` Jan Beulich
2023-03-14 20:56 ` [PATCH v3 4/6] vpci: restrict unhandled read/write operations for guests Volodymyr Babchuk
2023-03-17 8:37 ` Roger Pau Monné
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