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Date: Fri, 8 May 2015 06:27:21 -0700 From: "tip-bot for Peter Zijlstra (Intel)" <tipbot@...or.com> To: linux-tip-commits@...r.kernel.org Cc: tglx@...utronix.de, mingo@...nel.org, oleg@...hat.com, hpa@...or.com, raghavendra.kt@...ux.vnet.ibm.com, daniel@...ascale.com, akpm@...ux-foundation.org, paolo.bonzini@...il.com, david.vrabel@...rix.com, linux-kernel@...r.kernel.org, riel@...hat.com, doug.hatch@...com, konrad.wilk@...cle.com, scott.norton@...com, boris.ostrovsky@...cle.com, bp@...en8.de, torvalds@...ux-foundation.org, paulmck@...ux.vnet.ibm.com, Waiman.Long@...com, peterz@...radead.org Subject: [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) <peterz@...radead.org> AuthorDate: Fri, 24 Apr 2015 14:56:36 -0400 Committer: Ingo Molnar <mingo@...nel.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) <peterz@...radead.org> Signed-off-by: Waiman Long <Waiman.Long@...com> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org> Cc: Andrew Morton <akpm@...ux-foundation.org> Cc: Boris Ostrovsky <boris.ostrovsky@...cle.com> Cc: Borislav Petkov <bp@...en8.de> Cc: Daniel J Blueman <daniel@...ascale.com> Cc: David Vrabel <david.vrabel@...rix.com> Cc: Douglas Hatch <doug.hatch@...com> Cc: H. Peter Anvin <hpa@...or.com> Cc: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com> Cc: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Oleg Nesterov <oleg@...hat.com> Cc: Paolo Bonzini <paolo.bonzini@...il.com> Cc: Paul E. McKenney <paulmck@...ux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@...radead.org> Cc: Raghavendra K T <raghavendra.kt@...ux.vnet.ibm.com> Cc: Rik van Riel <riel@...hat.com> Cc: Scott J Norton <scott.norton@...com> Cc: Thomas Gleixner <tglx@...utronix.de> Cc: virtualization@...ts.linux-foundation.org Cc: xen-devel@...ts.xenproject.org Link: http://lkml.kernel.org/r/1429901803-29771-8-git-send-email-Waiman.Long@hp.com Signed-off-by: Ingo Molnar <mingo@...nel.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> #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 * -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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