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Message-ID: <20150928060537.GC2684@gmail.com>
Date: Mon, 28 Sep 2015 08:05:37 +0200
From: Ingo Molnar <mingo@...nel.org>
To: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc: linux-kernel@...r.kernel.org, msalter@...hat.com,
linux@...ck-us.net, oleg@...hat.com, sasha.levin@...cle.com
Subject: Re: [GIT PULL rcu/urgent] Fix two more 4.3 regressions
* Paul E. McKenney <paulmck@...ux.vnet.ibm.com> wrote:
> Hello, Ingo,
>
> This series contains two small fixes for regressions introduced during
> the past merge window:
>
> 1. Recent versions of gcc are fatally confused by use of a const
> int variable for array bounds in inline functions, one of which
> was introduced by 114b7fd4b (rcu: Create rcu_sync infrastructure).
> For more information on the gcc bug, see:
>
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67055#c13
>
> This workaround for that gcc bug, courtesy of Oleg Nesterov,
> simply substitutes the constant expression for the two uses of
> the const int variable.
>
> 2. Commit 2cd6ffafec06 (rcu: Extend expedited funnel locking
> to rcu_data structure) extended contention-reducing
> funnel locking from the rcu_node structures to the rcu_data
> structures, but failed to create a separate lock class for the
> rcu_sched_data structures, which is needed due to the fact that
> synchronize_rcu_expedited() invokes synchronize_sched_expedited().
> In the absence of this separate lock class, lockdep can give
> false-positive splats. This commit therefore creates the
> required lock class so that lockdep can see that there is in
> fact no deadlock.
>
> Both fixes have been exposed to -next and 0day Test Robot testing.
>
> These changes are available in the git repository at:
>
> git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git for-mingo
>
> for you to fetch changes up to 19a5ecde086a6a5287978b12ae948fa691b197b7:
>
> rcu: Suppress lockdep false positive for rcp->exp_funnel_mutex (2015-09-20 21:01:22 -0700)
>
> ----------------------------------------------------------------
> Oleg Nesterov (1):
> rcu: Change _wait_rcu_gp() to work around GCC bug 67055
>
> Paul E. McKenney (1):
> rcu: Suppress lockdep false positive for rcp->exp_funnel_mutex
>
> include/linux/rcupdate.h | 11 +++++------
> kernel/rcu/tree.c | 5 +++++
> 2 files changed, 10 insertions(+), 6 deletions(-)
Pulled, thanks a lot Paul!
Ingo
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