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 state as it was at checkpoint moment we need a way to setup ticks back. So as a counterpart of read() the write() takes ticks number from the userspace and updates internal timer ticks accordingly. CC: Shawn Landden CC: Thomas Gleixner CC: Andrew Morton CC: Andrey Vagin CC: Pavel Emelyanov CC: Vladimir Davydov Signed-off-by: Cyrill Gorcunov --- fs/timerfd.c | 21 +++++++++++++++++++++ 1 file changed, 21 insertions(+) Index: linux-2.6.git/fs/timerfd.c =================================================================== --- linux-2.6.git.orig/fs/timerfd.c +++ linux-2.6.git/fs/timerfd.c @@ -311,10 +311,31 @@ static int timerfd_show(struct seq_file (unsigned long long)t.it_interval.tv_nsec); } + +static ssize_t timerfd_write(struct file *file, const char __user *buf, + size_t count, loff_t *ppos) +{ + struct timerfd_ctx *ctx = file->private_data; + u64 ticks = 0; + + if (count < sizeof(ticks)) + return -EINVAL; + + if (get_user(ticks, (u64 __user *) buf)) + return -EFAULT; + + spin_lock_irq(&ctx->wqh.lock); + ctx->ticks = ticks; + spin_unlock_irq(&ctx->wqh.lock); + + return sizeof(ticks); +} + static const struct file_operations timerfd_fops = { .release = timerfd_release, .poll = timerfd_poll, .read = timerfd_read, + .write = timerfd_write, .llseek = noop_llseek, .show_fdinfo = timerfd_show, }; -- 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/