On Mon, 5 Nov 2012, Huang Ying wrote: > In current runtime PM implementation, the active child count of the > parent device may be decreased if the runtime PM of the child device > is disabled and forbidden. For example, to unbind a PCI driver with a > PCI device, the following code path is possible: > > pci_device_remove > pm_runtime_set_suspended > __pm_runtime_set_status > atomic_add_unless(&parent->power.child_count, -1, 0) > > That is, the parent device may be suspended, even if the runtime PM of > child device is forbidden to be suspended. This violate the rule that > parent is allowed to be suspended only after all its children are > suspended, and may cause issue.
This doesn't sound like a correct description of the situation. The rule is not violated. After pm_runtime_set_suspended runs, the child _is_ suspended. Thus there's no reason not to allow the parent to be suspended. The problem -- if there really is one -- is that a driver can put a device into the suspended state by calling pm_runtime_disable followed by pm_runtime_set_suspended, even if the usage count is > 0. I'm not so sure this should count as a problem. Generally devices aren't disabled for runtime PM unless something is wrong. Under those circumstances, the meaning of pm_runtime_forbid isn't very well defined. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
