[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <4F7174F0.1080504@cn.fujitsu.com>
Date: Tue, 27 Mar 2012 16:06:08 +0800
From: Lai Jiangshan <laijs@...fujitsu.com>
To: paulmck@...ux.vnet.ibm.com
CC: linux-kernel@...r.kernel.org, mingo@...e.hu, dipankar@...ibm.com,
akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
josh@...htriplett.org, niv@...ibm.com, tglx@...utronix.de,
peterz@...radead.org, rostedt@...dmis.org, Valdis.Kletnieks@...edu,
dhowells@...hat.com, eric.dumazet@...il.com, darren@...art.com,
fweisbec@...il.com, patches@...aro.org,
torvalds@...ux-foundation.org
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
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists