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Groups > linux.kernel > #1240724

[PATCH tip/core/rcu 12/13] locking/percpu-rwsem: Clean up the lockdep annotations in percpu_down_read()

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From: Oleg Nesterov <oleg@redhat.com>

Based on Peter Zijlstra's earlier patch.

Change percpu_down_read() to use __down_read(), this way we can
do rwsem_acquire_read() unconditionally at the start to make this
code more symmetric and clean.

Originally-From: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 kernel/locking/percpu-rwsem.c | 10 +++++-----
 1 file changed, 5 insertions(+), 5 deletions(-)

diff --git a/kernel/locking/percpu-rwsem.c b/kernel/locking/percpu-rwsem.c
index 02a726dd9adc..f231e0bb311c 100644
--- a/kernel/locking/percpu-rwsem.c
+++ b/kernel/locking/percpu-rwsem.c
@@ -70,14 +70,14 @@ static bool update_fast_ctr(struct percpu_rw_semaphore *brw, unsigned int val)
 void percpu_down_read(struct percpu_rw_semaphore *brw)
 {
 	might_sleep();
-	if (likely(update_fast_ctr(brw, +1))) {
-		rwsem_acquire_read(&brw->rw_sem.dep_map, 0, 0, _RET_IP_);
+	rwsem_acquire_read(&brw->rw_sem.dep_map, 0, 0, _RET_IP_);
+
+	if (likely(update_fast_ctr(brw, +1)))
 		return;
-	}
 
-	down_read(&brw->rw_sem);
+	/* Avoid rwsem_acquire_read() and rwsem_release() */
+	__down_read(&brw->rw_sem);
 	atomic_inc(&brw->slow_read_ctr);
-	/* avoid up_read()->rwsem_release() */
 	__up_read(&brw->rw_sem);
 }
 EXPORT_SYMBOL_GPL(percpu_down_read);
-- 
2.5.2

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Thread

[PATCH tip/core/rcu 0/13] percpu-rwsem patches for 4.4 "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-06 18:50 +0200
  [PATCH tip/core/rcu 02/13] locking/percpu-rwsem: Export symbols for locktorture "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-06 18:50 +0200
  [PATCH tip/core/rcu 07/13] rcu_sync: Add CONFIG_PROVE_RCU checks "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-06 18:50 +0200
  [PATCH tip/core/rcu 05/13] rcu: Create rcu_sync infrastructure "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-06 18:50 +0200
  [PATCH tip/core/rcu 01/13] locktorture: Support rtmutex torturing "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-06 18:50 +0200
    [PATCH tip/core/rcu 09/13] locking/percpu-rwsem: Make percpu_free_rwsem() after kzalloc() safe "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-06 18:50 +0200
    [PATCH tip/core/rcu 04/13] torture: Consolidate cond_resched_rcu_qs() into stutter_wait() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-06 18:50 +0200
    [PATCH tip/core/rcu 12/13] locking/percpu-rwsem: Clean up the lockdep annotations in percpu_down_read() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-06 18:50 +0200
    [PATCH tip/core/rcu 08/13] rcu_sync: Introduce rcu_sync_dtor() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-06 18:50 +0200
    [PATCH tip/core/rcu 06/13] rcu_sync: Simplify rcu_sync using new rcu_sync_ops structure "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-06 18:50 +0200
    [PATCH tip/core/rcu 11/13] locking/percpu-rwsem: Fix the comments outdated by rcu_sync "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-06 18:50 +0200
    [PATCH tip/core/rcu 13/13] rcu_sync: Cleanup the CONFIG_PROVE_RCU checks "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-06 19:00 +0200
    [PATCH tip/core/rcu 03/13] locktorture: Add torture tests for percpu_rwsem "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-06 19:00 +0200
    [PATCH tip/core/rcu 10/13] locking/percpu-rwsem: Make use of the rcu_sync infrastructure "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-06 19:00 +0200
  Re: [PATCH tip/core/rcu 0/13] percpu-rwsem patches for 4.4 Josh Triplett <josh@joshtriplett.org> - 2015-10-06 19:50 +0200
    Re: [PATCH tip/core/rcu 0/13] percpu-rwsem patches for 4.4 Oleg Nesterov <oleg@redhat.com> - 2015-10-06 21:00 +0200
      Re: [PATCH tip/core/rcu 0/13] percpu-rwsem patches for 4.4 "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-06 21:40 +0200
        Re: [PATCH tip/core/rcu 0/13] percpu-rwsem patches for 4.4 Josh Triplett <josh@joshtriplett.org> - 2015-10-06 22:40 +0200

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