> 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. It's a bit more subtle because you often have other interactions. In particular people often come unstuck on del_timer_sync or waiting for workqueues and IRQs to finish (even in free_irq) while holding a lock that the handler needs to take. Alan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
