linux-kernel - Re: [RESEND][RFC PATCH v2] waitfd

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Message-ID: <20090107171922.GA18000@redhat.com>
Date:	Wed, 7 Jan 2009 18:19:22 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Casey Dahlin <cdahlin@...hat.com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Randy Dunlap <randy.dunlap@...cle.com>,
	Roland McGrath <roland@...hat.com>,
	Davide Libenzi <davidel@...ilserver.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>
Subject: Re: [RESEND][RFC PATCH v2] waitfd

On 01/07, Ingo Molnar wrote:
>
> (Cc:-ed a few more folks who might be interested in this)
>
> * Casey Dahlin <cdahlin@...hat.com> wrote:
>
> > +asmlinkage long sys_waitfd(int which, pid_t upid, int options, int unused)
> > +{
> > +	int ufd;
> > +	struct waitfd_ctx *ctx;
> > +
> > +	/* Just to make sure we don't end up with a sys_waitfd4 */
> > +	(void)unused;
>
> looks a bit silly ...
>
> > +
> > +	if (options & ~(WNOHANG|WEXITED|WSTOPPED|WCONTINUED))
> > +		return -EINVAL;
> > +	if (!(options & (WEXITED|WSTOPPED|WCONTINUED)))
> > +		return -EINVAL;
> > +
> > +	ctx = kmalloc(sizeof(*ctx), GFP_KERNEL);
> > +	if (!ctx)
> > +		return -ENOMEM;
> > +
> > +	ctx->ops = options;
> > +	ctx->upid = upid;
> > +	ctx->which = which;
> > +
> > +	ufd = anon_inode_getfd("[waitfd]", &waitfd_fops, ctx,
> > +			       (options & WNOHANG) ? O_NONBLOCK : 0);

minor nit...

Please note that unlike other sys_...fd() syscalls, sys_waitfd()
doesn't allow to pass O_CLOEXEC. Looks like we need a separate
"flags" argument...

Also, ioctl(FIONBIO) or fcntl(O_NONBLOCK) have no effect on
waitfd, not very good.

I'd suggest to remove WNOHANG from waitfd_ctx->ops and treat
(->f_flags & O_NONBLOCK) as WNOHANG.

(can't resist, ->ops is not the best name ;)

Oleg.

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