Re: acpi_memhotplug.c: don't allow to eject the memory device if it is being used

[Wen Congyang <wency@cn.fujitsu.com>]

At 11/06/2012 10:05 PM, Dan Carpenter Wrote:
> On Tue, Nov 06, 2012 at 10:10:11AM +0800, Wen Congyang wrote:
>> At 11/06/2012 02:11 AM, Dan Carpenter Wrote:
>>> Hello Wen Congyang,
>>>
>>> The patch 306859f13dc1: "acpi_memhotplug.c: don't allow to eject the
>>> memory device if it is being used" from Nov 3, 2012, leads to the
>>> following Smatch warning:
>>> drivers/acpi/acpi_memhotplug.c:367 acpi_memory_remove_memory()
>>> 	 warn: inconsistent returns mutex:&mem_device->list_lock:
>>> 	locked (357,361) unlocked (367)
>>
>> Thanks for pointing it out.
>>
>> The patch 306859f13dc1 is in akpm's tree, and it conflicts with another
>> patch in linux-pm's tree. So Andrew Morton drops them.
>>
>> I will resend them based on linux-pm's next tree.
> 
> Ok. Today's linux-next version 85fcb3758c10e "ACPI / memory-hotplug:
> introduce a mutex lock to protect the list in acpi_memory_device"
> has a similar problem and should be fixed as well.
> 
>    319  static int acpi_memory_remove_memory(struct acpi_memory_device *mem_device)
>    320  {
>    321          int result;
>    322          struct acpi_memory_info *info, *n;
>    323  
>    324          mutex_lock(&mem_device->list_lock);
>    325          list_for_each_entry_safe(info, n, &mem_device->res_list, list) {
>    326                  if (info->enabled) {
>    327                          result = remove_memory(info->start_addr, info->length);
>    328                          if (result)
>    329                                  return result;
>                                         ^^^^^^^^^^^^^
> We are still holding the lock here.

Yes, I found this problem.

Thanks
Wen Congyang

> 
>    330                  }
>    331  
>    332                  list_del(&info->list);
>    333                  kfree(info);
>    334          }
>    335          mutex_unlock(&mem_device->list_lock);
>    336  
>    337          return 0;
>    338  }
> 
> regards,
> dan carpenter
> 
>