Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751627AbaFJQff (ORCPT ); Tue, 10 Jun 2014 12:35:35 -0400 Received: from mail-la0-f53.google.com ([209.85.215.53]:63173 "EHLO mail-la0-f53.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750969AbaFJQfe (ORCPT ); Tue, 10 Jun 2014 12:35:34 -0400 Date: Tue, 10 Jun 2014 20:35:30 +0400 From: Cyrill Gorcunov To: Thomas Gleixner Cc: 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: <20140610163530.GF2243@moon> References: <20140428212517.200264067@openvz.org> <20140428213301.507657833@openvz.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Thu, May 22, 2014 at 06:58:19AM +0900, Thomas Gleixner wrote: > > > > So what wakes a potential waiter in read/poll? > > And who is updating timerfd_create(2) ? Thomas, could you please take a look if the approach below is acceptable? If it will be fine I update manpage then. --- From: Cyrill Gorcunov Subject: timerfd: Implement timerfd_ioctl method to restore timerfd_ctx::ticks The read() of timerfd files allows to fetch the number of timer ticks while there is no way to set it back from userspace. To restore the timer's state as it was at checkpoint moment we need a path to bring @ticks back. Initially I thought about writing ticks back via write() interface but it seems such API is somehow obscure. Instead implement timerfd_ioctl() method with TFD_IOC_SET_TICKS command which requires CAP_SYS_RESOURCE capability to be able to set @ticks into arbitrary value. Note this command doesn't wake up readers/waiters and its purpose only to serve C/R needs (for same sake I wrapped code with CONFIG_CHECKPOINT_RESTORE). Still if needed the ioctl may be extended for new commands and CONFIG_CHECKPOINT_RESTORE dropped off. CC: Thomas Gleixner CC: Andrew Morton CC: Andrey Vagin CC: Pavel Emelyanov CC: Vladimir Davydov Signed-off-by: Cyrill Gorcunov --- fs/timerfd.c | 31 +++++++++++++++++++++++++++++++ include/linux/timerfd.h | 5 +++++ 2 files changed, 36 insertions(+) Index: linux-2.6.git/fs/timerfd.c =================================================================== --- linux-2.6.git.orig/fs/timerfd.c +++ linux-2.6.git/fs/timerfd.c @@ -313,11 +313,42 @@ static int timerfd_show(struct seq_file } #endif +#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 (!capable(CAP_SYS_RESOURCE)) + return -EPERM; + if (get_user(ticks, (u64 __user *)arg)) + return -EFAULT; + spin_lock_irq(&ctx->wqh.lock); + ctx->ticks = ticks; + spin_unlock_irq(&ctx->wqh.lock); + break; + } + default: + ret = -ENOTTY; + break; + } + + return ret; +} +#endif + static const struct file_operations timerfd_fops = { .release = timerfd_release, .poll = timerfd_poll, .read = timerfd_read, .llseek = noop_llseek, +#ifdef CONFIG_CHECKPOINT_RESTORE + .unlocked_ioctl = timerfd_ioctl, +#endif #ifdef CONFIG_PROC_FS .show_fdinfo = timerfd_show, #endif Index: linux-2.6.git/include/linux/timerfd.h =================================================================== --- linux-2.6.git.orig/include/linux/timerfd.h +++ linux-2.6.git/include/linux/timerfd.h @@ -11,6 +11,9 @@ /* For O_CLOEXEC and O_NONBLOCK */ #include +/* For _IO helpers */ +#include + /* * CAREFUL: Check include/asm-generic/fcntl.h when defining * new flags, since they might collide with O_* ones. We want @@ -29,4 +32,6 @@ /* Flags for timerfd_settime. */ #define TFD_SETTIME_FLAGS (TFD_TIMER_ABSTIME | TFD_TIMER_CANCEL_ON_SET) +#define TFD_IOC_SET_TICKS _IOW('T', 0, u64) + #endif /* _LINUX_TIMERFD_H */ -- 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/