linux-kernel - Re: [patch 3/3] timerfd: Implement write method

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Message-ID: <20140611090914.GA12336@paralelels.com>
Date:	Wed, 11 Jun 2014 13:09:15 +0400
From:	Andrew Vagin <avagin@...allels.com>
To:	Cyrill Gorcunov <gorcunov@...il.com>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>, <avagin@...nvz.org>,
	<xemul@...allels.com>, <vdavydov@...allels.com>,
	Michael Kerrisk <mtk.manpages@...il.com>
Subject: Re: [patch 3/3] timerfd: Implement write method

On Wed, Jun 11, 2014 at 11:51:25AM +0400, Cyrill Gorcunov wrote:
> On Wed, Jun 11, 2014 at 11:27:43AM +0400, Andrew Vagin wrote:

...

> +#ifdef CONFIG_CHECKPOINT_RESTORE
> +static long timerfd_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
> +{
> +	struct timerfd_ctx *ctx = file->private_data;
> +	int ret = 0;
> +
> +	switch (cmd) {
> +	case TFD_IOC_SET_TICKS: {
> +		u64 ticks;
> +
> +		if (get_user(ticks, (u64 __user *)arg))
> +			return -EFAULT;
> +		spin_lock_irq(&ctx->wqh.lock);
> +		ctx->ticks = ticks;
> +		if (ticks)
> +			wake_up_locked(&ctx->wqh);

Setting ticks to zero is equivalent to timerfd_read(), isn't it?
So do we need to re-arme the timer, if it's periodic?

> +		spin_unlock_irq(&ctx->wqh.lock);
> +		break;
> +	}
> +	default:
> +		ret = -ENOTTY;
> +		break;
> +	}
> +
> +V	return ret;
> +}
> +#endif
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