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From: guoren@kernel.org
To: palmer@rivosinc.com, arnd@arndb.de, mingo@redhat.com,
	will@kernel.org, longman@redhat.com, boqun.feng@gmail.com
Cc: linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org,
	linux-kernel@vger.kernel.org, Guo Ren <guoren@linux.alibaba.com>,
	Guo Ren <guoren@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>
Subject: [PATCH V7 1/5] asm-generic: ticket-lock: Remove unnecessary atomic_read
Date: Tue, 28 Jun 2022 04:17:03 -0400	[thread overview]
Message-ID: <20220628081707.1997728-2-guoren@kernel.org> (raw)
In-Reply-To: <20220628081707.1997728-1-guoren@kernel.org>

From: Guo Ren <guoren@linux.alibaba.com>

Remove unnecessary atomic_read in arch_spin_value_unlocked(lock),
because the value has been in lock. This patch could prevent
arch_spin_value_unlocked contend spin_lock data again.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
---
 include/asm-generic/spinlock.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/asm-generic/spinlock.h b/include/asm-generic/spinlock.h
index fdfebcb050f4..f1e4fa100f5a 100644
--- a/include/asm-generic/spinlock.h
+++ b/include/asm-generic/spinlock.h
@@ -84,7 +84,9 @@ static __always_inline int arch_spin_is_contended(arch_spinlock_t *lock)
 
 static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
 {
-	return !arch_spin_is_locked(&lock);
+	u32 val = lock.counter;
+
+	return ((val >> 16) == (val & 0xffff));
 }
 
 #include <asm/qrwlock.h>
-- 
2.36.1


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WARNING: multiple messages have this Message-ID (diff)
From: guoren@kernel.org
To: palmer@rivosinc.com, arnd@arndb.de, mingo@redhat.com,
	will@kernel.org, longman@redhat.com, boqun.feng@gmail.com
Cc: linux-riscv@lists.infradead.org, linux-arch@vger.kernel.org,
	linux-kernel@vger.kernel.org, Guo Ren <guoren@linux.alibaba.com>,
	Guo Ren <guoren@kernel.org>,
	Peter Zijlstra <peterz@infradead.org>
Subject: [PATCH V7 1/5] asm-generic: ticket-lock: Remove unnecessary atomic_read
Date: Tue, 28 Jun 2022 04:17:03 -0400	[thread overview]
Message-ID: <20220628081707.1997728-2-guoren@kernel.org> (raw)
In-Reply-To: <20220628081707.1997728-1-guoren@kernel.org>

From: Guo Ren <guoren@linux.alibaba.com>

Remove unnecessary atomic_read in arch_spin_value_unlocked(lock),
because the value has been in lock. This patch could prevent
arch_spin_value_unlocked contend spin_lock data again.

Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
Signed-off-by: Guo Ren <guoren@kernel.org>
Cc: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Palmer Dabbelt <palmer@rivosinc.com>
---
 include/asm-generic/spinlock.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/asm-generic/spinlock.h b/include/asm-generic/spinlock.h
index fdfebcb050f4..f1e4fa100f5a 100644
--- a/include/asm-generic/spinlock.h
+++ b/include/asm-generic/spinlock.h
@@ -84,7 +84,9 @@ static __always_inline int arch_spin_is_contended(arch_spinlock_t *lock)
 
 static __always_inline int arch_spin_value_unlocked(arch_spinlock_t lock)
 {
-	return !arch_spin_is_locked(&lock);
+	u32 val = lock.counter;
+
+	return ((val >> 16) == (val & 0xffff));
 }
 
 #include <asm/qrwlock.h>
-- 
2.36.1


  reply	other threads:[~2022-06-28  8:17 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-28  8:17 [PATCH V7 0/5] riscv: Add qspinlock support with combo style guoren
2022-06-28  8:17 ` guoren
2022-06-28  8:17 ` guoren [this message]
2022-06-28  8:17   ` [PATCH V7 1/5] asm-generic: ticket-lock: Remove unnecessary atomic_read guoren
2022-06-28 18:05   ` Waiman Long
2022-06-28 18:05     ` Waiman Long
2022-06-29  2:12     ` Guo Ren
2022-06-29  2:12       ` Guo Ren
2022-06-29  8:27   ` David Laight
2022-06-29  8:27     ` David Laight
2022-07-01 15:18     ` Guo Ren
2022-07-01 15:18       ` Guo Ren
2022-07-04  9:52   ` Peter Zijlstra
2022-07-04  9:52     ` Peter Zijlstra
2022-07-04 11:10     ` Guo Ren
2022-07-04 11:10       ` Guo Ren
2022-06-28  8:17 ` [PATCH V7 2/5] asm-generic: ticket-lock: Use the same struct definitions with qspinlock guoren
2022-06-28  8:17   ` guoren
2022-06-28  8:17 ` [PATCH V7 3/5] asm-generic: ticket-lock: Move into ticket_spinlock.h guoren
2022-06-28  8:17   ` guoren
2022-06-28  8:17 ` [PATCH V7 4/5] asm-generic: spinlock: Add combo spinlock (ticket & queued) guoren
2022-06-28  8:17   ` guoren
2022-06-28 18:13   ` Waiman Long
2022-06-28 18:13     ` Waiman Long
2022-06-29  1:17     ` Guo Ren
2022-06-29  1:17       ` Guo Ren
2022-06-29  1:34       ` Waiman Long
2022-06-29  1:34         ` Waiman Long
2022-06-29  2:29         ` Guo Ren
2022-06-29  2:29           ` Guo Ren
2022-06-29  7:08         ` Arnd Bergmann
2022-06-29  7:08           ` Arnd Bergmann
2022-06-29  8:24           ` Guo Ren
2022-06-29  8:24             ` Guo Ren
2022-06-29  8:29             ` Arnd Bergmann
2022-06-29  8:29               ` Arnd Bergmann
2022-07-01 12:18               ` Guo Ren
2022-07-01 12:18                 ` Guo Ren
2022-06-29 12:53           ` Waiman Long
2022-06-29 12:53             ` Waiman Long
2022-07-04  9:57   ` Peter Zijlstra
2022-07-04  9:57     ` Peter Zijlstra
2022-07-04 13:13     ` Guo Ren
2022-07-04 13:13       ` Guo Ren
2022-07-04 13:45       ` Peter Zijlstra
2022-07-04 13:45         ` Peter Zijlstra
2022-06-28  8:17 ` [PATCH V7 5/5] riscv: Add qspinlock support guoren
2022-06-28  8:17   ` guoren

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