Messages in this thread | | | Date | Fri, 19 Apr 2013 13:04:54 +0200 | From | Lars-Peter Clausen <> | Subject | Re: [PATCH 2/2] dma:of: Use a mutex to protect the of_dma_list |
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On 04/19/2013 12:13 PM, Arnd Bergmann wrote: > On Friday 19 April 2013, Lars-Peter Clausen wrote: > >> This is rather ugly and unnecessary and non of the current users of >> of_dma_controller_free() check it's return value anyway. Instead protect the >> list by a mutex. The mutex will be held as long as a request operation is in >> progress. So if of_dma_controller_free() is called while a request operation is >> in progress it will be put to sleep and only wake up once the request operation >> has finished. >> >> This means that it is no longer possible to register or unregister OF DMA >> controllers from a context where it's not possible to sleep. But I doubt that >> we'll ever need this. >> >> Also rename of_dma_get_controller back to of_dma_find_controller. >> >> Signed-off-by: Lars-Peter Clausen <lars@metafoo.de> > > I guess we could also fix it by turning the reference count into a proper > kref with kref_put calling the destructor, but your solution seems to solve > the problem just as well.
Well, It's not only about the of_dma struct, e.g. the of_dma's of_dma_data field usually points to some driver allocated data. If we do not block in of_dma_controller_free() this data might be freed while the controller is still in use.
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