Hi Chris, On Thu, 1 Sep 2016 21:08:54 +0000, Chris Packham wrote: > On 09/02/2016 12:12 AM, Guenter Roeck wrote: > > This puts a heavy burden on the system, forcing it to run every ms, just for > > the unlikely case of driver removal. Why is quick removal so important ? > > If it is, we'll have to find a better solution. > > The particular use case we have is a chassis based system with an > adt7470 on a removable fan-tray. The problem is that when the fan tray > is removed it takes auto_update_interval/1000 seconds for the update > thread to stop and the i2c device to be removed. In the intervening time > a new fan-tray could have been installed. Thanks for the clarification. An actual use case makes it easier to think about solutions. > On 09/01/2016 08:18 PM, Jean Delvare wrote: > > > > This change looks terribly costly to me. In order to shorten the > > duration of a rare event (you don't "rmmod adt7470" on a regular basis, > > do you?) > > It's worse than that. We're not doing rmmod, hardware is physically > being removed. I wouldn't call it "worse", it's pretty much the same to me. > > you increase the cost of a kernel thread which runs all the > > time. I'm afraid this msleep_interruptible(1) is going to prevent the > > CPU from entering low power states at all, leading to an increased > > system temperature and power consumption. Have you compared the output > > of "powertop" (specifically the "Idle stats" section) before and after > > your patch? > > > > Is there no way to voluntarily interrupt this long msleep_interruptible? > > If there is I'd like to know. That would be the ideal solution for us. I've never done that before myself so I don't know more than you. stackoverflow has a few promising pointers though: http://stackoverflow.com/questions/26050745/is-there-a-way-inside-the-kernel-of-killing-a-kernel-kthread-just-like-kill-9 http://stackoverflow.com/questions/36344295/wakeup-a-kernel-thread-that-is-in-sleep-using-msleep My own research suggests that maybe calling wake_up_process(data->auto_update) right after kthread_stop() may work. Have you tried that? I only find it suspect that nobody else in the kernel is doing that. -- Jean Delvare SUSE L3 Support -- To unsubscribe from this list: send the line "unsubscribe linux-hwmon" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
