Re: [PATCH] IPC: message queue stealing feature introduced

[Stanislav Kinsbursky]

15.02.2012 13:40, Eric Dumazet ÐÐÑÐÑ:
> Le mercredi 15 fÃvrier 2012 Ã 13:08 +0400, Stanislav Kinsbursky a
> Ãcrit :
> > This patch is required for checkpoint/restore in userspace project.
> > C/r requires some way to get all pending IPC messages without deleting them for
> > 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_STEAL for sys_msgrcv() system call
> > introduced.
> > If this flag is set, then passed struct msgbuf pointer will be used for storing
> > array of structures:
> >
> > struct msgbuf_a {
> > 	long mtype;         /* type of message */
> > 	size_t msize;       /* size of message */
> > 	char mtext[0];      /* message text */
> > };
>
> This structure is not 32/64 bit safe and will need compat tricks.
>
> +                       ret = do_steal_msg(mtext, arrsz, msg);
> +                       if (ret<  0) {
> +                               msg = ERR_PTR(ret);
> +                               goto out_unlock;
> +                       }
> +                       mtext += ret + sizeof(struct msgbuf_a);
> +                       arrsz -= ret + sizeof(struct msgbuf_a);
>
> I cant see where alignement requirements are met.
>
> (ret should be rounded up to a multiple of alignof(struct msgbuf_a)


Thanks for reply, Eric.
Will fix and resend soon.

--
Best regards,
Stanislav Kinsbursky
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