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Date: Mon, 30 Aug 2004 23:40:57 -0700
From: Andrew Morton <akpm@osdl.org>
To: Jakub Jelinek <jakub@redhat.com>
Cc: roland@redhat.com, mtk-lkml@gmx.net, torvalds@osdl.org, drepper@redhat.com,
       linux-kernel@vger.kernel.org, michael.kerrisk@gmx.net,
       tonnerre@thundrix.ch
Subject: Re: [PATCH] waitid system call
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Jakub Jelinek <jakub@redhat.com> wrote:
>
> On Mon, Aug 30, 2004 at 11:04:46PM -0700, Roland McGrath wrote:
>  > +			/*
>  > +			 * For a WNOHANG return, clear out all the fields
>  > +			 * we would set so the user can easily tell the
>  > +			 * difference.
>  > +			 */
>  > +			if (!retval)
>  > +				retval = put_user(0, &infop->si_signo);
>  > +			if (!retval)
>  > +				retval = put_user(0, &infop->si_errno);
>  > +			if (!retval)
>  > +				retval = put_user(0, &infop->si_code);
>  > +			if (!retval)
>  > +				retval = put_user(0, &infop->si_pid);
>  > +			if (!retval)
>  > +				retval = put_user(0, &infop->si_uid);
>  > +			if (!retval)
>  > +				retval = put_user(0, &infop->si_status);
> 
>  Is it really necessary to check the exit code after each put_user?
>  	if (!retval && access_ok(VERIFY_WRITE, infop, sizeof(*infop)))) {
>  		retval = __put_user(0, &infop->si_signo);
>  		retval |= __put_user(0, &infop->si_errno);
>  		retval |= __put_user(0, &infop->si_code);
>  		retval |= __put_user(0, &infop->si_pid);
>  		retval |= __put_user(0, &infop->si_uid);
>  		retval |= __put_user(0, &infop->si_status);
>  	}
>  is what kernel usually does when filling multiple structure members.

I don't think it matters much.  Taking seven trips into the fault handler
where one would do seems a bit dumb though.