Messages in this thread | | | From | Rusty Russell <> | Subject | Re: [PATCH 1/2] module: use rcu to protect module list read | Date | Tue, 13 Mar 2012 11:07:58 +1030 |
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On Sat, 10 Mar 2012 07:25:57 -0800, Eric Dumazet <eric.dumazet@gmail.com> wrote: > Le samedi 10 mars 2012 à 22:20 +0800, Cong Wang a écrit : > > Now the read of module list is protected by preempt disable + *_rcu > > list operations, this is odd, as RCU read lock should be able to > > protect it directly. This patch makes the read of module list > > protected by RCU read lock and the write still protected by > > module_mutex. > > > > Problem is that your patch does more than that. > > In set_all_modules_text_rw() and set_all_modules_text_ro() you removed > the mutex in favor of rcu_read_lock() > > Also, module code uses synchronize_sched(), not synchronize_rcu()
Yes, but only for paranoia. Really, it's vs. stop_machine().
> Take a look at Documentation/RCU/whatisRCU.txt and see that > preempt_disable() / preempt_enable() are documented as a right protect > code, in line 333. > > You added races in /proc/modules as well.
I'm surprised that patch didn't warn... CONFIG_DEBUG_ATOMIC_SLEEP=y might help here....
Cheers, Rusty. -- How could I marry someone with more hair than me? http://baldalex.org -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.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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