Commit-ID: 2aa79af64263190eec610422b07f60e99a7d230a
Gitweb: http://git.kernel.org/tip/2aa79af64263190eec610422b07f60e99a7d230a
Author: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
AuthorDate: Fri, 24 Apr 2015 14:56:36 -0400
Committer: Ingo Molnar <mingo@xxxxxxxxxx>
CommitDate: Fri, 8 May 2015 12:36:58 +0200
locking/qspinlock: Revert to test-and-set on hypervisors
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 (Intel) <peterz@xxxxxxxxxxxxx>
Signed-off-by: Waiman Long <Waiman.Long@xxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Daniel J Blueman <daniel@xxxxxxxxxxxxx>
Cc: David Vrabel <david.vrabel@xxxxxxxxxx>
Cc: Douglas Hatch <doug.hatch@xxxxxx>
Cc: H. Peter Anvin <hpa@xxxxxxxxx>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Paolo Bonzini <paolo.bonzini@xxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Scott J Norton <scott.norton@xxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1429901803-29771-8-git-send-email-Waiman.Long@xxxxxx
Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
---
arch/x86/include/asm/qspinlock.h | 14 ++++++++++++++
include/asm-generic/qspinlock.h | 7 +++++++
kernel/locking/qspinlock.c | 3 +++
3 files changed, 24 insertions(+)
diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h
index e2aee82..f079b70 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>
#define queued_spin_unlock queued_spin_unlock
@@ -15,6 +16,19 @@ static inline void queued_spin_unlock(struct qspinlock *lock)
smp_store_release((u8 *)lock, 0);
}
+#define virt_queued_spin_lock virt_queued_spin_lock
+
+static inline bool virt_queued_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 569abcd..83bfb87 100644
--- a/include/asm-generic/qspinlock.h
+++ b/include/asm-generic/qspinlock.h
@@ -111,6 +111,13 @@ static inline void queued_spin_unlock_wait(struct qspinlock *lock)
cpu_relax();
}
+#ifndef virt_queued_spin_lock
+static __always_inline bool virt_queued_spin_lock(struct qspinlock *lock)
+{
+ return false;
+}
+#endif
+
/*
* Initializier
*/
diff --git a/kernel/locking/qspinlock.c b/kernel/locking/qspinlock.c
index 0338721..fd31a47 100644
--- a/kernel/locking/qspinlock.c
+++ b/kernel/locking/qspinlock.c
@@ -249,6 +249,9 @@ void queued_spin_lock_slowpath(struct qspinlock *lock, u32 val)
BUILD_BUG_ON(CONFIG_NR_CPUS >= (1U << _Q_TAIL_CPU_BITS));
+ if (virt_queued_spin_lock(lock))
+ return;
+
/*
* wait for in-progress pending->locked hand-overs
*
--
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