lkml.org 
[lkml]   [2015]   [Jan]   [20]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH v14 07/11] qspinlock: Revert to test-and-set on hypervisors
Date
From: Peter Zijlstra <peterz@infradead.org>

When we detect a hypervisor (!paravirt, see qspinlock paravirt support
patches), revert to a simple test-and-set lock to avoid the horrors
of queue preemption.

Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Waiman Long <Waiman.Long@hp.com>
---
arch/x86/include/asm/qspinlock.h | 14 ++++++++++++++
include/asm-generic/qspinlock.h | 7 +++++++
kernel/locking/qspinlock.c | 3 +++
3 files changed, 24 insertions(+), 0 deletions(-)

diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h
index a6a8762..05a77fe 100644
--- a/arch/x86/include/asm/qspinlock.h
+++ b/arch/x86/include/asm/qspinlock.h
@@ -1,6 +1,7 @@
#ifndef _ASM_X86_QSPINLOCK_H
#define _ASM_X86_QSPINLOCK_H

+#include <asm/cpufeature.h>
#include <asm-generic/qspinlock_types.h>

#ifndef CONFIG_X86_PPRO_FENCE
@@ -20,6 +21,19 @@ static inline void queue_spin_unlock(struct qspinlock *lock)

#endif /* !CONFIG_X86_PPRO_FENCE */

+#define virt_queue_spin_lock virt_queue_spin_lock
+
+static inline bool virt_queue_spin_lock(struct qspinlock *lock)
+{
+ if (!static_cpu_has(X86_FEATURE_HYPERVISOR))
+ return false;
+
+ while (atomic_cmpxchg(&lock->val, 0, _Q_LOCKED_VAL) != 0)
+ cpu_relax();
+
+ return true;
+}
+
#include <asm-generic/qspinlock.h>

#endif /* _ASM_X86_QSPINLOCK_H */
diff --git a/include/asm-generic/qspinlock.h b/include/asm-generic/qspinlock.h
index aafb7b4..82054a1 100644
--- a/include/asm-generic/qspinlock.h
+++ b/include/asm-generic/qspinlock.h
@@ -111,6 +111,13 @@ static inline void queue_spin_unlock_wait(struct qspinlock *lock)
cpu_relax();
}

+#ifndef virt_queue_spin_lock
+static __always_inline bool virt_queue_spin_lock(struct qspinlock *lock)
+{
+ return false;
+}
+#endif
+
/*
* Initializier
*/
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index fb0e988..1c1926a 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -257,6 +257,9 @@ void queue_spin_lock_slowpath(struct qspinlock *lock, u32 val)

BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS));

+ if (virt_queue_spin_lock(lock))
+ return;
+
/*
* wait for in-progress pending->locked hand-overs
*
--
1.7.1


\
 
 \ /
  Last update: 2015-01-20 21:41    [W:0.092 / U:0.268 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site