Hello, On Thu, 2 May 2013, Paul E. McKenney wrote: > mainline, and missed the one that you added. Revisiting that, a > question: > > > +#ifdef CONFIG_PREEMPT_RCU > > +#define PREEMPT_RCU_OFFSET 1 > > Does this really want to be "1" instead of PREEMPT_OFFSET? In this case when CONFIG_PREEMPT_RCU is enabled we (RCU) do not touch the preempt counters. Instead, the units are accounted in current->rcu_read_lock_nesting: #define rcu_preempt_depth() (current->rcu_read_lock_nesting) __rcu_read_lock: current->rcu_read_lock_nesting++; and the path is __might_sleep -> preempt_count_equals -> rcu_preempt_depth For now both places do not use PREEMPT_OFFSET: - #define inc_preempt_count() add_preempt_count(1) - __rcu_read_lock: current->rcu_read_lock_nesting++; so, ... it does not matter much for me. In short, the trick is in preempt_count_equals() where preempt_offset is a combination of preempt count and RCU preempt depth: #ifdef CONFIG_PREEMPT_RCU #define PREEMPT_RCU_OFFSET (0 /* preempt */ + 1 /* RCU */) #else #define PREEMPT_RCU_OFFSET (PREEMPT_CHECK_OFFSET + 0 /* RCU */) #endif Let me know for your preference about this definition... Regards -- Julian Anastasov <ja@xxxxxx> -- To unsubscribe from this list: send the line "unsubscribe lvs-devel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
