51 lines
1.9 KiB
Diff
51 lines
1.9 KiB
Diff
From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
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Date: Tue, 19 Sep 2017 15:36:42 -0700
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Subject: [PATCH] rcu: Suppress lockdep false-positive ->boost_mtx complaints
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Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/4.14/older/patches-4.14.15-rt13.tar.xz
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Upstream commit bcda31a2659497df39d6bedfbdf17498b4f4ac89
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RCU priority boosting uses rt_mutex_init_proxy_locked() to initialize an
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rt_mutex structure in locked state held by some other task. When that
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other task releases it, lockdep complains (quite accurately, but a bit
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uselessly) that the other task never acquired it. This complaint can
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suppress other, more helpful, lockdep complaints, and in any case it is
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a false positive.
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This commit therefore switches from rt_mutex_unlock() to
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rt_mutex_futex_unlock(), thereby avoiding the lockdep annotations.
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Of course, if lockdep ever learns about rt_mutex_init_proxy_locked(),
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addtional adjustments will be required.
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Suggested-by: Peter Zijlstra <peterz@infradead.org>
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Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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kernel/rcu/tree_plugin.h | 5 ++---
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1 file changed, 2 insertions(+), 3 deletions(-)
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--- a/kernel/rcu/tree_plugin.h
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+++ b/kernel/rcu/tree_plugin.h
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@@ -31,11 +31,10 @@
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#include <linux/smpboot.h>
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#include <uapi/linux/sched/types.h>
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#include "../time/tick-internal.h"
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+#include "../locking/rtmutex_common.h"
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#ifdef CONFIG_RCU_BOOST
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-#include "../locking/rtmutex_common.h"
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-
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/*
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* Control variables for per-CPU and per-rcu_node kthreads. These
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* handle all flavors of RCU.
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@@ -530,7 +529,7 @@ void rcu_read_unlock_special(struct task
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/* Unboost if we were boosted. */
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if (IS_ENABLED(CONFIG_RCU_BOOST) && drop_boost_mutex)
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- rt_mutex_unlock(&rnp->boost_mtx);
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+ rt_mutex_futex_unlock(&rnp->boost_mtx);
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/*
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* If this was the last task on the expedited lists,
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