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From: Nicholas Piggin <npiggin@gmail.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Nicholas Piggin <npiggin@gmail.com>,
	Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
	Waiman Long <longman@redhat.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	"linux-kernel @ vger . kernel . org"
	<linux-kernel@vger.kernel.org>
Subject: [PATCH v2 10/12] locking/qspinlock: paravirt use simple trylock in case idx overflows
Date: Wed, 13 Jul 2022 17:07:02 +1000	[thread overview]
Message-ID: <20220713070704.308394-11-npiggin@gmail.com> (raw)
In-Reply-To: <20220713070704.308394-1-npiggin@gmail.com>

The mcs node overflow fallback locking case does not have to use
pv_hybrid_queued_unfair_trylock as the trylock, which reduces the
differences between pv and !pv cases.

This was likely an artifact of function renaming making it use the pv
trylock, which is not a bug but it is unexpected.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
---
 kernel/locking/qspinlock.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index df6d8af8f2a9..2ebb946a6b80 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -800,13 +800,8 @@ static __always_inline void queued_spin_lock_mcs_queue(struct qspinlock *lock, b
 	 */
 	if (unlikely(idx >= MAX_NODES)) {
 		lockevent_inc(lock_no_node);
-		if (paravirt) {
-			while (!pv_hybrid_queued_unfair_trylock(lock))
-				cpu_relax();
-		} else {
-			while (!queued_spin_trylock(lock))
-				cpu_relax();
-		}
+		while (!queued_spin_trylock(lock))
+			cpu_relax();
 		goto release;
 	}
 
-- 
2.35.1


  parent reply	other threads:[~2022-07-13  7:08 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-07-13  7:06 [PATCH v2 00/12] locking/qspinlock: simplify code generation Nicholas Piggin
2022-07-13  7:06 ` [PATCH v2 01/12] locking/qspinlock: remove pv_node abstraction Nicholas Piggin
2022-07-13  7:06 ` [PATCH v2 02/12] locking/qspinlock: inline mcs_spinlock functions into qspinlock Nicholas Piggin
2022-07-13  7:06 ` [PATCH v2 03/12] locking/qspinlock: split common mcs queueing code into its own function Nicholas Piggin
2022-07-13  7:06 ` [PATCH v2 04/12] locking/qspinlock: move pv lock word helpers into qspinlock.c Nicholas Piggin
2022-07-13  7:06 ` [PATCH v2 05/12] locking/qspinlock: be less clever with the preprocessor Nicholas Piggin
2022-07-13  7:06 ` [PATCH v2 06/12] locking/qspinlock: merge qspinlock_paravirt.h into qspinlock.c Nicholas Piggin
2022-07-14 14:16   ` kernel test robot
2022-07-29  3:49     ` Nicholas Piggin
2022-07-14 16:42   ` kernel test robot
2022-07-14 20:28   ` kernel test robot
2022-07-13  7:06 ` [PATCH v2 07/12] locking/qspinlock: remove arch qspinlock_paravirt.h includes Nicholas Piggin
2022-07-14 13:14   ` kernel test robot
2022-07-14 16:21   ` kernel test robot
2022-07-13  7:07 ` [PATCH v2 08/12] locking/qspinlock: stop renaming queued_spin_lock_slowpath to native_queued_spin_lock_slowpath Nicholas Piggin
2022-07-13  7:07 ` [PATCH v2 09/12] locking/qspinlock: rename __pv_init_lock_hash to pv_spinlocks_init Nicholas Piggin
2022-07-13  7:07 ` Nicholas Piggin [this message]
2022-07-13  7:07 ` [PATCH v2 11/12] locking/qspinlock: separate pv_wait_node from the non-paravirt path Nicholas Piggin
2022-07-13  7:07 ` [PATCH v2 12/12] locking/qspinlock: simplify pv_wait_head_or_lock calling scheme Nicholas Piggin

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