Re: [GIT PULL rcu/urgent] Fixes for RCU regressions

From: Ingo Molnar
Date: Fri Oct 12 2012 - 03:53:57 EST



* Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx> wrote:

> Hello, Ingo,
>
> This series fixes some RCU regressions in 3.7.
>
> Kirill A. Shutemov found a case where synchronize_rcu() is invoked
> from a CPU-hotplug notifier, which, with RCU's shiny new kthread-based
> grace-period implementation, results in deadlock. The first commit
> in this series fixes this deadlock by introducing RCU-specific
> synchronization, so that RCU grace periods exclude only RCU's CPU-hotplug
> notifiers, not the entire CPU-hotplug operation. Kirill successfully
> tested this commit (as have I), and it has furthermore been exposed to
> -next testing.
>
> The other commit in this series adds a warning to the new RCU_USER_QS
> and RCU_USER_QS_FORCE Kconfig options, noting that these features,
> though reasonably stable, are probably not ready for millions of users.
> This commit affects only the Kconfig help text.
>
> These changes are available in the git repository at:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git rcu/urgent
>
> Thanx, Paul
>
> ------------------>
> Frederic Weisbecker (1):
> rcu: Advise most users not to enable RCU user mode
>
> Paul E. McKenney (1):
> rcu: Grace-period initialization excludes only RCU notifier
>
> init/Kconfig | 12 ++++++++++++
> kernel/rcutree.c | 21 ++++++++++-----------
> kernel/rcutree.h | 6 ++++++
> 3 files changed, 28 insertions(+), 11 deletions(-)

Pulled, thanks a lot Paul!

Ingo
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