Re: frequent lockups in 3.18rc4

From: DÃniel Fraga
Date: Tue Dec 02 2014 - 13:47:42 EST

On Tue, 2 Dec 2014 10:42:02 -0800
"Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx> wrote:

> I was actually suggesting something a bit different. Instead of bisecting
> by release, bisect by code. The procedure is as follows:
> 1. I figure out some reliable way of making RCU allow preemption to
> be disabled for some RCU read-side critical sections, but not for
> others. I send you the patch, which has rcu_read_lock_test()
> as well as rcu_read_lock().
> 2. You build a kernel without my Kconfig hack, with my patch from
> #1 above, and build a kernel with CONFIG_PREEMPT=y (which of
> course implies CONFIG_TREE_PREEMPT_RCU=y, given that you are
> building without my Kconfig hack).
> 3. You make a list of all the rcu_read_lock() uses in the kernel
> (or ask me to provide it). You change the rcu_read_lock()
> calls in the first half of this list to rcu_read_lock_test().
> If the kernel locks up as easily with this change as it did
> change half of the remaining rcu_read_lock() calls to
> rcu_read_lock_test(). If the kernel is much more resistant
> to lockup, change half of the rcu_read_lock_test() calls
> back to rcu_read_lock().

Ok Paul, I want to do everything I can to help you debug this.

So can you provide me the list you mentioned at point 3 (or
tell me how can I get it)? If you guide me through this, I can do
whatever you need. Thanks!

Linux 3.17.0-rc6-00235-gb94d525: Shuffling Zombie Juror
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