Messages in this thread | | | Date | Mon, 29 Jun 2015 08:36:01 -0700 | From | Arjan van de Ven <> | Subject | Re: [RFC PATCH 1/2] regmap: add configurable lock class key for lockdep |
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On 6/29/2015 8:32 AM, Mark Brown wrote: > On Mon, Jun 29, 2015 at 07:35:20AM -0700, Arjan van de Ven wrote: > >> lockdep assumes that there is a known lock hierarchy, at least known >> to the developer. > >> seems like for regmap there isn't > > It's not that there's no heirachy of locks, it's that lockdep is unable > to understand what's going on since it's making simplifying assumptions > that just aren't true. If I remember the problem correctly it's > grouping all locks allocated in the same place into one class which > doesn't work at all for scenarios where you've got a generic interface > providing services to many devices which may be stacked on top of each > other.
but the stacking *IS* a lock hierarchy.
it just seems that the hierarchy is implied rather than explicit.
>> (I would be interested to know how you avoid ABBA deadlocks btw, >> can you have 2 devices, one with a hierarchy one way, and another >> with the hierarchy the other way?) > > I'm not sure I fully understand what you mean here, sorry - do you mean > in terms of classes or individual devices? The relationships between > devices are all device and system defined, individual regmaps should be > treated as separate classes. From this perspective it's basically > eqivalent to asking how the mutex code avoids misuse of mutexes.
well what I meant is inividual devices/ranges
like device A is on devmap A but then ends up using devmap B underneath (e.g. the lock nesting case)
what prevents there from being a device B that is on devmap B but that uses devmap A underneath
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