On Monday, 24 of December 2007, Alan Stern wrote: > On Mon, 24 Dec 2007, Rafael J. Wysocki wrote: > > > Hi, > > > > Some device drivers register CPU hotplug notifiers and use them to destroy > > device objects when removing the corresponding CPUs and to create these objects > > when adding the CPUs back. > > > > Unfortunately, this is not the right thing to do during suspend/hibernation, > > since in that cases the CPU hotplug notifiers are called after suspending > > devices and before resuming them, so the operations in question are carried > > out on the objects representing suspended devices which shouldn't be > > unregistered behing the PM core's back. Although right now it usually doesn't > > lead to any practical complications, it will predictably deadlock if > > gregkh-driver-pm-acquire-device-locks-prior-to-suspending.patch is applied. > > > > The solution is to prevent drivers from removing/adding devices from within > > CPU hotplug notifiers during suspend/hibernation using the FROZEN bit > > in the notifier's action argument. The following three patches modify the > > MSR, x86-64 MCE and cpuid drivers along these lines. > > Do we need to worry about the possibility that when the system wakes up > from hibernation, the set of usable CPUs might be smaller than it was > beforehand? This is possible in error conditions. > Is any special handling needed for this, or is it already accounted for? Hm, well. The cleanest thing would be to allow the drivers to remove the device objects on CPU_UP_CANCELED_FROZEN, which means that we weren't able to bring the CPU up during a resume, but still that will deadlock with gregkh-driver-pm-acquire-device-locks-prior-to-suspending.patch. Greetings, Rafael - To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
