Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755390AbaFKJwv (ORCPT ); Wed, 11 Jun 2014 05:52:51 -0400 Received: from mail-la0-f50.google.com ([209.85.215.50]:45243 "EHLO mail-la0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755340AbaFKJwu (ORCPT ); Wed, 11 Jun 2014 05:52:50 -0400 Date: Wed, 11 Jun 2014 13:52:46 +0400 From: Cyrill Gorcunov To: Andrew Vagin Cc: Thomas Gleixner , LKML , Andrew Morton , avagin@openvz.org, xemul@parallels.com, vdavydov@parallels.com, Michael Kerrisk Subject: Re: [patch 3/3] timerfd: Implement write method Message-ID: <20140611095246.GJ2243@moon> References: <20140428212517.200264067@openvz.org> <20140428213301.507657833@openvz.org> <20140610163530.GF2243@moon> <20140611072743.GA10612@paralelels.com> <20140611075125.GI2243@moon> <20140611090914.GA12336@paralelels.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20140611090914.GA12336@paralelels.com> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jun 11, 2014 at 01:09:15PM +0400, Andrew Vagin wrote: > 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? I must admit I'm not really sure if we should rearm it in such case. In general @ticks are zeroified in case of timer-setup/cancel/read. - lets consider someone armed the timer it triggered but no read done yet, instead ioctl called and @ticks are set to zero, then call for read() and it returns zero to caller not rearming the timer (in current patch approach and non-block read) - in turn if we rearm timer on @ticks = 0 in ioctl this makes it close to behaviour of read() function (which in turn look to me as a duplication of read() interface). That said, I'm not sure yet... -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/