On Tuesday, 20 of November 2007, Mark M. Hoffman wrote: > Hi all: > > * Alan Stern <stern@xxxxxxxxxxxxxxxxxxx> [2007-11-19 15:27:14 -0500]: > > On Mon, 19 Nov 2007, Rudolf Marek wrote: > > > > > Hello all, > > > >>> gives coretemp_cpu_callback -> coretemp_device_remove -> > > > >>> platform_device_unregister, so coretemp seems to be what I have and you don't. > > > > > > > > Yes. > > > > > > > > For the coretemp developers: coretemp_cpu_callback() needs to be more > > > > careful about what it does. During a system sleep transition (suspend, > > > > hibernate, resume) it isn't possible to register or unregister a > > > > device. Attempts to register will fail and attempts to unregister will > > > > block until the system sleep is over -- and for this callback that > > > > means hanging. > > > > > > Well I wrote the driver. Thanks for the clarification. If I recall correctly I > > > looked how this part should be done from others drivers. Now while checking > > > what happened to the file, seems Rafael added something related. > > > > > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commit;h=8bb7844286fb8c9fce6f65d8288aeb09d03a5e0d > > > > That does look like it was meant for exactly this sort of situation. > > > > > > It's not clear what the best way is to fix this. Perhaps the CPU > > > > notification should be sent along with a special flag indicating that > > > > the CPU transition is part of a system sleep (although this seems > > > > racy). Perhaps the driver should notice when a system sleep begins, > > > > and defer all CPU-change handling until after the sleep is over. > > > > > > maybe it does exist? CPU_DOWN_PREPARE ? > > > > > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=blob;f=Documentation/cpu-hotplug.txt;hb=HEAD > > > > > > Unfortunately I'm not very familiar with this, calling the > > > coretemp_device_remove from CPU_DOWN_PREPARE would help? Looking at microcode > > > driver, seems it just hide sysfs interface from user. > > AFAICT from that documentation, it would have been better to unregister > the device on CPU_DOWN_PREPARE anyway. CPU_DEAD seems to be too late - > it's already gone by then. > > > I'm not sure exactly what you want to do here. But it seems like a > > waste to unregister the coretemp devices at the start of a system sleep > > and then register them back at the end. > > > > Could you simply leave the devices registered throughout the entire > > sleep? Of course, at the end you would have to check that all the CPUs > > really did come back up, and unregister the devices for the CPUs that > > are still offline. > > Is it possible to unregister a driver on CPU_DOWN_PREPARE_FROZEN? No. In that case the suspend core is holding the device's mutex and your attempt to unregister it will deadlock with it. Do you _have_ _to_ unregister the device at all? Why don't you just leave it registered on CPU_DOWN_PREPARE_FROZEN? The CPU is not going away physically in this case and it's _guaranteed_ that _cpu_up() will be called on it as soon as the hibernation image is ready or we are back from suspend. > If so, then the simplest fix would be the patch below (Jiri: feel free to > try it). Otherwise it would take a bit of refactoring to bring the sysfs > interface down/up for suspend/resume. > > commit ce9c7b78c839a6304696d90083eac08baad524ce > Author: Mark M. Hoffman <mhoffman@xxxxxxxxxxxxx> > Date: Tue Nov 20 07:51:50 2007 -0500 > > hwmon: (coretemp) fix suspend/resume hang > > Signed-off-by: Mark M. Hoffman <mhoffman@xxxxxxxxxxxxx> I'd do it like this: > diff --git a/drivers/hwmon/coretemp.c b/drivers/hwmon/coretemp.c > index 5c82ec7..afe2d31 100644 > --- a/drivers/hwmon/coretemp.c > +++ b/drivers/hwmon/coretemp.c > @@ -338,10 +338,12 @@ static int coretemp_cpu_callback(struct notifier_block *nfb, > switch (action) { > case CPU_ONLINE: > case CPU_ONLINE_FROZEN: > + case CPU_DOWN_FAILED: > coretemp_device_add(cpu); + case CPU_DOWN_FAILED_FROZEN: > break; > - case CPU_DEAD: > - case CPU_DEAD_FROZEN: > + case CPU_DOWN_PREPARE: > coretemp_device_remove(cpu); + case CPU_DOWN_PREPARE_FROZEN: > break; > } Greetings, Rafael -- "Premature optimization is the root of all evil." - Donald Knuth _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
