linux-kernel - Re: [PATCH 4/6 OPTION-A version 3] completion: Add new wait_for_completion_timeout

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Message-ID: <20120328173858.GC18944@redhat.com>
Date:	Wed, 28 Mar 2012 19:38:58 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Boaz Harrosh <bharrosh@...asas.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>,
	linux-security-module@...r.kernel.org, Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Paul Turner <pjt@...gle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	NFS list <linux-nfs@...r.kernel.org>,
	Trond Myklebust <Trond.Myklebust@...app.com>,
	"Bhamare, Sachin" <sbhamare@...asas.com>,
	David Howells <dhowells@...hat.com>,
	Eric Paris <eparis@...hat.com>,
	"Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>,
	Kay Sievers <kay.sievers@...y.org>,
	James Morris <jmorris@...ei.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Greg KH <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	"keyrings@...ux-nfs.org" <keyrings@...ux-nfs.org>
Subject: Re: [PATCH 4/6 OPTION-A version 3] completion: Add new
	wait_for_completion_timeout_state

On 03/26, Boaz Harrosh wrote:
>
> +int __sched
> +wait_for_completion_timeout_state(struct completion *x,
> +				  unsigned long timeout, int state)
> +{
> +	long t;
> +	int ret;
> +
> +	if (!timeout)
> +		timeout = MAX_SCHEDULE_TIMEOUT;
> +
> +	switch (state) {
> +	default:
> +		WARN_ON_ONCE(1);
> +		/* fall through */
> +	case 0:
> +		state = TASK_UNINTERRUPTIBLE;
> +		break;

Well, this looks strange, imho. If the caller wants TASK_UNINTERRUPTIBLE,
it should simply pass TASK_UNINTERRUPTIBLE.
wait_for_completion_timeout_state(state => 0) looks confusing, and this
is not symmetrical wrt other states.

> +	t = wait_for_common(x, timeout, state);
> +	if (likely(t > 0)) {
> +		ret = 0;
> +	} else  {
> +		if (t < 0)
> +			ret = t;
> +		else
> +			ret = -ETIMEDOUT;
> +	}
> +	return ret;

I tend to agree with Peter. This is the common helper, probably it
will have more users. We shouldn't throw out the positive return
value, it can be useful.

call_usermodehelper_exec() can simply do

	retval = wait_for_common(...);

	if (retval > 0)
		retval = sub_info->retval;
	else if (!retval)
		retval = -ETIMEDOUT;

Oleg.

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