[tip:locking/core] locking/qspinlock: Revert to test-and-set on hypervisors
Commit-ID: 2aa79af64263190eec610422b07f60e99a7d230a
Gitweb: http://git.kernel.org/tip/2aa79af64263190eec610422b07f60e99a7d230a
Author: Peter Zijlstra (Intel)
AuthorDate: Fri, 24 Apr 2015 14:56:36 -0400
Committer: Ingo Molnar
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)
Signed-off-by: Waiman Long
Signed-off-by: Peter Zijlstra (Intel)
Cc: Andrew Morton
Cc: Boris Ostrovsky
Cc: Borislav Petkov
Cc: Daniel J Blueman
Cc: David Vrabel
Cc: Douglas Hatch
Cc: H. Peter Anvin
Cc: Konrad Rzeszutek Wilk
Cc: Linus Torvalds
Cc: Oleg Nesterov
Cc: Paolo Bonzini
Cc: Paul E. McKenney
Cc: Peter Zijlstra
Cc: Raghavendra K T
Cc: Rik van Riel
Cc: Scott J Norton
Cc: Thomas Gleixner
Cc: virtualizat...@lists.linux-foundation.org
Cc: xen-de...@lists.xenproject.org
Link:
http://lkml.kernel.org/r/1429901803-29771-8-git-send-email-waiman.l...@hp.com
Signed-off-by: Ingo Molnar
---
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
#include
#definequeued_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(>val, 0, _Q_LOCKED_VAL) != 0)
+ cpu_relax();
+
+ return true;
+}
+
#include
#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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[tip:locking/core] locking/qspinlock: Revert to test-and-set on hypervisors
Commit-ID: 2aa79af64263190eec610422b07f60e99a7d230a
Gitweb: http://git.kernel.org/tip/2aa79af64263190eec610422b07f60e99a7d230a
Author: Peter Zijlstra (Intel) pet...@infradead.org
AuthorDate: Fri, 24 Apr 2015 14:56:36 -0400
Committer: Ingo Molnar mi...@kernel.org
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) pet...@infradead.org
Signed-off-by: Waiman Long waiman.l...@hp.com
Signed-off-by: Peter Zijlstra (Intel) pet...@infradead.org
Cc: Andrew Morton a...@linux-foundation.org
Cc: Boris Ostrovsky boris.ostrov...@oracle.com
Cc: Borislav Petkov b...@alien8.de
Cc: Daniel J Blueman dan...@numascale.com
Cc: David Vrabel david.vra...@citrix.com
Cc: Douglas Hatch doug.ha...@hp.com
Cc: H. Peter Anvin h...@zytor.com
Cc: Konrad Rzeszutek Wilk konrad.w...@oracle.com
Cc: Linus Torvalds torva...@linux-foundation.org
Cc: Oleg Nesterov o...@redhat.com
Cc: Paolo Bonzini paolo.bonz...@gmail.com
Cc: Paul E. McKenney paul...@linux.vnet.ibm.com
Cc: Peter Zijlstra pet...@infradead.org
Cc: Raghavendra K T raghavendra...@linux.vnet.ibm.com
Cc: Rik van Riel r...@redhat.com
Cc: Scott J Norton scott.nor...@hp.com
Cc: Thomas Gleixner t...@linutronix.de
Cc: virtualizat...@lists.linux-foundation.org
Cc: xen-de...@lists.xenproject.org
Link:
http://lkml.kernel.org/r/1429901803-29771-8-git-send-email-waiman.l...@hp.com
Signed-off-by: Ingo Molnar mi...@kernel.org
---
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
#definequeued_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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