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Date: Fri, 14 Nov 2008 09:03:20 +0800 From: Lai Jiangshan <laijs@...fujitsu.com> To: paulmck@...ux.vnet.ibm.com CC: Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>, Andrew Morton <akpm@...ux-foundation.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, corbet@....net Subject: Re: [PATCH] rcupdate: move synchronize_sched() back to rcupdate.c V2 Paul E. McKenney wrote: > On Thu, Nov 13, 2008 at 10:48:33AM +0800, Lai Jiangshan wrote: >> Hi, Paul, >> >> Could you add a RCU document about unloadable modules for kernel? > > You thinking in terms of an ASCII version of > http://lwn.net/Articles/217484/? > > If so, please see attached patch and let me know what you think. > Being too lazy to convert the cartoon to ASCII graphics, I simply > left a URL to the .jpg on the LWN website. Thus we need an ack/nack > from Jon Corbet (CCed). Hi, Paul Thank you. it's a very good document. I found several modules which need rcu_barrier(). So I'm going to do some cleanup for them. A document for rcu_barrier() will help these cleanup patches be accepted easily by maintainers. Lai. > > Of course, an alternative is to simply include the URL of the original > LWN article in 00-INDEX. Thoughts? > > Thanx, Paul > > Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com> > --- > +The code for rcu_barrier() is as follows: > + > + 1 void rcu_barrier(void) > + 2 { > + 3 BUG_ON(in_interrupt()); > + 4 /* Take cpucontrol mutex to protect against CPU hotplug */ > + 5 mutex_lock(&rcu_barrier_mutex); > + 6 init_completion(&rcu_barrier_completion); > + 7 atomic_set(&rcu_barrier_cpu_count, 0); > + 8 on_each_cpu(rcu_barrier_func, NULL, 0, 1); > + 9 wait_for_completion(&rcu_barrier_completion); > +10 mutex_unlock(&rcu_barrier_mutex); > +11 } > + this is a little old. > + > +Quick Quiz #2: Why is there no rcu_barrier_bh()? > + > +Answer: Because no one has needed it yet. As soon as someone needs to > + use call_rcu_bh() from within an unloadable module, they will > + need an rcu_barrier_bh(). > + add here. -- 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/
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