Re: [PATCH 3/3] Add disk hotswap support to libata RESEND #2

[Stefan Richter <stefanr@s5r6.in-berlin.de>]

George Anzinger wrote:
> Jim Ramsay wrote:
>> On 8/23/05, Jim Ramsay <jim.ramsay@gmail.com> wrote:
>>> I've applied this set
>>> of patches to a 2.6.11 kernel (with few problems) and ran into a bunch
>>> of "scheduling while atomic" errors when hotplugging a drive, culprit
>>> being probably scsi_sysfs.c
...
>> After further debugging, it appears that the problem is the debounce
>> timer in libata-core.c.
>>
>> Timers appear to operate in an atomic context, so timers should not be
>> allowed to call scsi_remove_device, which eventually schedules.
>>
>> Any suggestions on the best way to fix this?
> 
> Workqueue, perhaps.

The USB and IEEE 1394 subsystems have kernel threads which manage node 
additions and removals (usb/storage/usb.c, ieee1394/nodemgr.c). The add 
and remove functions of their storage drivers are called from these 
threads' non-atomic context. However if you don't need an own thread for 
any further bus management purposes, a workqueue looks suitable for hot 
plugging and unplugging.
-- 
Stefan Richter
-=====-=-=-= =--- ==---
http://arcgraph.de/sr/