On Thursday, February 14, 2013 08:45:14 PM Moore, Robert wrote: > > > -----Original Message----- > > From: Rafael J. Wysocki [mailto:rjw@xxxxxxx] > > Sent: Thursday, February 14, 2013 4:04 AM > > To: Moore, Robert > > Cc: Toshi Kani; ACPI Devel Maling List; LKML; Bjorn Helgaas; Jiang Liu; > > Yinghai Lu; Yasuaki Ishimatsu; Myron Stowe; linux-pci@xxxxxxxxxxxxxxx > > Subject: Re: [Update][PATCH] ACPI / hotplug: Fix concurrency issues and > > memory leaks > > > > On Thursday, February 14, 2013 02:31:22 AM Moore, Robert wrote: > > > > > > I thought about that, but actually there's no guarantee that the > > > > > > handle will be valid after _EJ0 as far as I can say. So the > > > > > > race condition is going to be there anyway and using struct > > > > > > acpi_device just makes it easier to avoid it. > > > > > > > > > > In theory, yes, a stale handle could be a problem, if _EJ0 > > > > > performs unload table and if ACPICA frees up its internal data > > > > > structure pointed by the handle as a result. But we should not > > > > > see such issue now since we do not support dynamic ACPI namespace > > yet. > > > > > > > > I'm waiting for information from Bob about that. If we can assume > > > > ACPI handles to be always valid, that will simplify things quite a > > bit. > > > > > > If a table is unloaded, all the namespace nodes for that table are > > > removed from the namespace, and thus any ACPI_HANDLE pointers go stale > > and invalid. > > > > OK, thanks! > > > > To me this means that we cannot assume a handle to stay valid between a > > notify handler and acpi_bus_hot_remove_device() run from a workqueue. > > > > Is there a mechanism in ACPICA to ensure that a handle won't become stale > > while a notify handler is running for it or is the OS responsible for > > ensuring that > > _EJ0 won't be run in parallel with notify handlers for device objects > > being ejected? > > > > It is up to the host. I was afraid that that might be the case. :-) So far the (Linux) host has been happily ignoring that potential problem, so I guess it can still be ignored for a while, although we'll need to address it eventually at one point. Thanks, Rafael -- I speak only for myself. Rafael J. Wysocki, Intel Open Source Technology Center. -- To unsubscribe from this list: send the line "unsubscribe linux-pci" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
