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Re: [PATCH v7 09/10] IPC: message queue copy feature introduced [message #48492 is a reply to message #48491]

Thu, 18 October 2012 12:41

Stanislav Kinsbursky is currently offline

Stanislav Kinsbursky
Messages: 683
Registered: October 2011

Senior Member

18.10.2012 16:09, Michael Kerrisk (man-pages) пишет:
>>> Is there somewhere a *detailed* description of how this feature would
>>> be used? Lacking that, it's really hard to see how anything sane and
>>> reliable can be done with MSG_COPY.
>>>
>>
>> These patches are used by CRIU already.
>> So, you can have a look at the CRIU source code:
>>
>> http://git.criu.org/?p=crtools.git ;a=blob;f=ipc_ns.c;h=9e259fefcfc04ec0556bb722921545552e1c69f 3;hb=HEAD
>>
>> Sanity and reliability on the level you are talking about can be achieved,
>> only if you'll freeze all message users before peeking.
>
> Okay -- that's the piece I was looking for. Thanks.
>
> In this scenario, how do you find all of the message users?

It looks like there is no way to how find these users.
But I don't really think, that this is necessary.
I.e. nothing protects the queue from reading by some alien (not expected)
process in real life.

> Or do you simply ensure that everything is frozen beforehand?
>

In this particular case - yes.

--
Best regards,
Stanislav Kinsbursky

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[Message index]

		[PATCH v7 09/10] IPC: message queue copy feature introduced By: Stanislav Kinsbursky on Thu, 18 October 2012 10:23
		Re: [PATCH v7 09/10] IPC: message queue copy feature introduced By: Michael Kerrisk (man- on Thu, 18 October 2012 10:39
		Re: [PATCH v7 09/10] IPC: message queue copy feature introduced By: Stanislav Kinsbursky on Thu, 18 October 2012 11:02
		Re: [PATCH v7 09/10] IPC: message queue copy feature introduced By: Michael Kerrisk (man- on Thu, 18 October 2012 11:18
		Re: [PATCH v7 09/10] IPC: message queue copy feature introduced By: Stanislav Kinsbursky on Thu, 18 October 2012 11:34
		Re: [PATCH v7 09/10] IPC: message queue copy feature introduced By: Michael Kerrisk (man- on Thu, 18 October 2012 11:55
		Re: [PATCH v7 09/10] IPC: message queue copy feature introduced By: Stanislav Kinsbursky on Thu, 18 October 2012 12:05
		Re: [PATCH v7 09/10] IPC: message queue copy feature introduced By: Michael Kerrisk (man- on Thu, 18 October 2012 12:09
		Re: [PATCH v7 09/10] IPC: message queue copy feature introduced By: Stanislav Kinsbursky on Thu, 18 October 2012 12:41
		Re: [PATCH v7 09/10] IPC: message queue copy feature introduced By: ebiederm on Thu, 18 October 2012 12:20
		Re: [PATCH v7 09/10] IPC: message queue copy feature introduced By: ebiederm on Thu, 18 October 2012 11:52
		Re: [PATCH v7 09/10] IPC: message queue copy feature introduced By: Stanislav Kinsbursky on Thu, 18 October 2012 14:40
		Re: [PATCH v7 09/10] IPC: message queue copy feature introduced By: ebiederm on Fri, 19 October 2012 00:52
		Re: [PATCH v7 09/10] IPC: message queue copy feature introduced By: Stanislav Kinsbursky on Fri, 19 October 2012 07:44

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