Messages in this thread | | | Date | Tue, 27 Mar 2012 16:06:08 +0800 | From | Lai Jiangshan <> | Subject | Re: [PATCH RFC] rcu: Make __rcu_read_lock() inlinable |
| |
On 03/26/2012 04:52 AM, Paul E. McKenney wrote:
> +void rcu_switch_from(void) > { > - current->rcu_read_lock_nesting++; > - barrier(); /* needed if we ever invoke rcu_read_lock in rcutree.c */ > + current->rcu_read_lock_nesting_save = > + __this_cpu_read(rcu_read_lock_nesting); > + barrier(); > + __this_cpu_write(rcu_read_lock_nesting, 0);
- __this_cpu_write(rcu_read_lock_nesting, 0); + __this_cpu_write(rcu_read_lock_nesting, 1);
if prev or next task has non-zero rcu_read_unlock_special, "__this_cpu_write(rcu_read_lock_nesting, 1)" will prevent wrong qs reporting when rcu_read_unlock() is called in any interrupt/tracing while doing switch_to().
> +} > + > +/* > + * Restore the incoming task's value for rcu_read_lock_nesting at the > + * end of a context switch. > + */ > +void rcu_switch_to(void) > +{ > + __this_cpu_write(rcu_read_lock_nesting, > + current->rcu_read_lock_nesting_save); > + barrier(); > + current->rcu_read_lock_nesting_save = 0; > }
- barrier(); - current->rcu_read_lock_nesting_save = 0;
rcu_read_lock_nesting_save is set but not used before next set here, just remove it.
I don't like it hooks too much into scheduler.
Approaches: 0) stay using function call 1) hook into kbuild(https://lkml.org/lkml/2011/3/27/170,https://lkml.org/lkml/2011/3/27/171) 2) hook into scheduler(still need more works for rcu_read_unlock()) 3) Add rcu_read_lock_nesting to thread_info like preempt_count 4) resolve header-file dependence
For me 3=4>1>2>0
Thanks, Lai
| |