| Re: [PATCH v4 8/9] IPC: message queue copy feature introduced [message #47803 is a reply to message #47485] |
Tue, 11 September 2012 15:03  |
Manfred Spraul
Messages: 4
Registered: August 2012
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Junior Member |
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On 08/13/2012 02:32 PM, Stanislav Kinsbursky wrote:
> This patch is required for checkpoint/restore in userspace.
> IOW, c/r requires some way to get all pending IPC messages without deleting
> them from the queue (checkpoint can fail and in this case tasks will be resumed,
> so queue have to be valid).
> To achive this, new operation flag MSG_COPY for sys_msgrcv() system call was
> introduced. If this flag was specified, then mtype is interpreted as number of
> the message to copy.
> If MSG_COPY is set, then kernel will allocate dummy message with passed size,
> and then use new copy_msg() helper function to copy desired message (instead of
> unlinking it from the queue).
>
> Notes:
> 1) Return -ENOSYS if MSG_COPY is specified, but CONFIG_CHECKPOINT_RESTORE is
> not set.
How is CONFIG_CHECKPOINT_RESTORE set?
I'm not sure, but I think it should be added to Kconfig.
--
Manfred
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