From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2] ARM: mcs lock: implement wfe-based polling for MCS locking
Date: Sun, 1 Jun 2014 12:30:32 +0100 [thread overview]
Message-ID: <1401622232-9918-1-git-send-email-will.deacon@arm.com> (raw)
This patch introduces a wfe-based polling loop for spinning on contended
MCS locks and waking up corresponding waiters when the lock is released.
Signed-off-by: Will Deacon <will.deacon@arm.com>
---
v1 => v2: Use SMP guards and dsb_sev() macro to ensure this compiles and
runs only on CPUs that can support v6k.
arch/arm/include/asm/mcs_spinlock.h | 23 +++++++++++++++++++++++
1 file changed, 23 insertions(+)
create mode 100644 arch/arm/include/asm/mcs_spinlock.h
diff --git a/arch/arm/include/asm/mcs_spinlock.h b/arch/arm/include/asm/mcs_spinlock.h
new file mode 100644
index 000000000000..f652ad65840a
--- /dev/null
+++ b/arch/arm/include/asm/mcs_spinlock.h
@@ -0,0 +1,23 @@
+#ifndef __ASM_MCS_LOCK_H
+#define __ASM_MCS_LOCK_H
+
+#ifdef CONFIG_SMP
+#include <asm/spinlock.h>
+
+/* MCS spin-locking. */
+#define arch_mcs_spin_lock_contended(lock) \
+do { \
+ /* Ensure prior stores are observed before we enter wfe. */ \
+ smp_mb(); \
+ while (!(smp_load_acquire(lock))) \
+ wfe(); \
+} while (0) \
+
+#define arch_mcs_spin_unlock_contended(lock) \
+do { \
+ smp_store_release(lock, 1); \
+ dsb_sev(); \
+} while (0)
+
+#endif /* CONFIG_SMP */
+#endif /* __ASM_MCS_LOCK_H */
--
1.9.2
reply other threads:[~2014-06-01 11:30 UTC|newest]
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