netdev - Re: [PATCH 32/32] aio: implement io

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Date:   Mon, 15 Jan 2018 09:53:10 +0100
From:   Christoph Hellwig <hch@....de>
To:     Jeff Moyer <jmoyer@...hat.com>
Cc:     Christoph Hellwig <hch@....de>, viro@...iv.linux.org.uk,
        Avi Kivity <avi@...lladb.com>, linux-aio@...ck.org,
        linux-fsdevel@...r.kernel.org, netdev@...r.kernel.org,
        linux-api@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 32/32] aio: implement io_pgetevents

On Fri, Jan 12, 2018 at 03:44:52PM -0500, Jeff Moyer wrote:
> Christoph Hellwig <hch@....de> writes:
> 
> > This is the io_getevents equivalent of ppoll/pselect and allows to
> > properly mix signals and aio completions (especially with IOCB_CMD_POLL)
> > and atomically executes the following sequence:
> >
> > 	sigset_t origmask;
> >
> > 	pthread_sigmask(SIG_SETMASK, &sigmask, &origmask);
> > 	ret = io_getevents(ctx, min_nr, nr, events, timeout);
> > 	pthread_sigmask(SIG_SETMASK, &origmask, NULL);
> >
> > Note that unlike many other signal related calls we do not pass a sigmask
> > size, as that would get us to 7 arguments, which aren't easily supported
> > by the syscall infrastructure.  It seems a lot less painful to just add a
> > new syscall variant in the unlikely case we're going to increase the
> > sigset size.
> 
> pselect, as an example, crams the sigmask and size together.  Why not
> just do that?  libaio can take care of setting that up.

Yes, I could try that.  It's just another double indirection for no
good reason.