Shaohua Li wrote: > On Thu, 2007-09-27 at 10:24 +0400, Alexey Starikovskiy wrote: >> Shaohua Li wrote: >>> On Thu, 2007-09-27 at 11:30 +0800, Zhang Rui wrote: >>>> Hi, all, >>>> >>>> I found a bug that linux/acpi may execute notify handler that >>>> has been removed. >>>> >>>> When a system notify(0~0x7f) is received, linux/acpi will >>>> first invoke the generic system notify handler (acpi_bus_notify) >>>> and then invoke the per-device notify handler if present. >>>> >>>> In my case, I add some code in acpi_bus_notify for battery >>>> hotplug support, so that the generic system notify handler will >>>> remove the battery device, including the per-device notify handler >>>> acpi_battery_notify() when receiving notification >>>> ACPI_NOTIFY_EJECT_REQUEST. >>>> But linux/acpi invokes the per-device notify handler soon and >>>> this breaks the system. >>>> >>>> Further more, device hot-removal is not the only case to encounter >>>> this bug. For example, linux/acpi receives a notification and adds it >>>> in the workqueue, and then the driver(notify handler) is removed >>>> before kacpid_notify invoke it... >>> For the non-hotplug case, adding a flush work queue just after notify >>> handler is removed should be ok. >> I think, the real problem with ACPI hotplug is that we know which devices might appear -- >> they are all enumerated in DSDT, but we don't add them until they appear. >> If we do .add for all devices in DSDT, and then just .start/.stop them as they appear/disappear, >> we will have to do much less work, and avoid a problem described above... > If a device is not present, you can't access any method of it. What is because you didn't call .add() yet, or already called .remove(), yes? > > The real problem here is ACPICA will call some drivers routines > (notification handler), but doesn't get a reference count of the driver > module. We just should be able to load drivers for declared, but physically absent devices. > > Thanks, > Shaohua - 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
