[RFC tip/locking/lockdep v6 11/20] lockdep: Fix recursive read lock related safe->unsafe detection

irq-safe -> irq-unsafe lock dependency is illegal, because it could introduce the "irq inversion" problem, that is when a irq-unsafe lock is held, some one else interrupts and tries to acquire irq-safe lock. And that case adds a temporary from irq-unsafe to irq-safe, as a result, deadlock. There

[RFC tip/locking/lockdep v6 11/20] lockdep: Fix recursive read lock related safe->unsafe detection

irq-safe -> irq-unsafe lock dependency is illegal, because it could introduce the "irq inversion" problem, that is when a irq-unsafe lock is held, some one else interrupts and tries to acquire irq-safe lock. And that case adds a temporary from irq-unsafe to irq-safe, as a result, deadlock. There