Grant Grundler wrote:
> On Sat, Sep 03, 2005 at 06:37:52PM -0500, Brian King wrote:
> ...
> 
>>Without the locking, we introduce a race condition.
>>
>>CPU 0                                           CPU 1
>>
>>					pci_block_user_cfg_access
>>						pci_save_state
>>pci_read_user_config_space
>>	check block_ucfg_access
>>						set block_ucfg_access
>>					other code that puts the device
>>					in a state such that it cannot
>>					handle read config i/o, such as
>>					running BIST.
>>
>>	pci read config
> 
> 
> Ok this is good example - I see what the problem is.
> You could use the following sequence too then:
> 	pci_block_user_cfg_access
> 		pci_save_state
> 		block_ucfg_access = 1
> 		mb()
> 		while (spin_is_locked(&pci_lock))
> 			relax_cpu();
> 
> Think this is sufficient?

That should work also. Here is an updated patch.


-- 
Brian King
eServer Storage I/O
IBM Linux Technology Center