On Thu, Sep 27, 2012 at 03:13:14PM +0100, Alan Cox wrote: > > as far as I know, nested locks are fine provided that you always take them > > in > > the same order and release them in the opposite order (lock A, lock B, > > unlock B, unlock A). So my conclusion is that nested spinlocks require > > potential regmap users of sta2x11 registers to take the sta2x11-mfd spinlock > > first. The pattern would be (sctl registers for instance): > > The release order does not matter. Taking AB and releasing AB or BA is > fine. Taking AB and dropping B and retaking B is fine. Taking AB and > somewhere else taking BA is not. There are performance reasons in some > cases why taking AB releasing A is best with locks, but thats generally > with sleepable locks. > thanks, I'd never really thought about the release pattern actually. In this particular case, though, B is inside the regmap code and is taken and released when a regmap call happens, so I think AB necessarily implies BA. For instance:
lock(A); regmap_read(...); /* Lock/unlock B */ unlock(A); Thanks Davide -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
