Messages in this thread Patch in this message | | | From | Julia Cartwright <> | Subject | [PATCH RT 07/22] rcu: Suppress lockdep false-positive ->boost_mtx complaints | Date | Mon, 6 Aug 2018 04:17:23 -0500 |
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From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
4.9.115-rt94-rc1 stable review patch. If you have any objection to the inclusion of this patch, let me know.
--- 8< --- 8< --- 8< --- [ Upstream commit 02a7c234e54052101164368ff981bd72f7acdd65 ]
RCU priority boosting uses rt_mutex_init_proxy_locked() to initialize an rt_mutex structure in locked state held by some other task. When that other task releases it, lockdep complains (quite accurately, but a bit uselessly) that the other task never acquired it. This complaint can suppress other, more helpful, lockdep complaints, and in any case it is a false positive.
This commit therefore switches from rt_mutex_unlock() to rt_mutex_futex_unlock(), thereby avoiding the lockdep annotations. Of course, if lockdep ever learns about rt_mutex_init_proxy_locked(), addtional adjustments will be required.
Suggested-by: Peter Zijlstra <peterz@infradead.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Julia Cartwright <julia@ni.com> --- kernel/rcu/tree_plugin.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 3d18d08e8382..510de72ad8a3 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -486,7 +486,7 @@ void rcu_read_unlock_special(struct task_struct *t) /* Unboost if we were boosted. */ if (IS_ENABLED(CONFIG_RCU_BOOST) && drop_boost_mutex) - rt_mutex_unlock(&rnp->boost_mtx); + rt_mutex_futex_unlock(&rnp->boost_mtx); /* * If this was the last task on the expedited lists, -- 2.18.0
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