From: Peter Zijlstra <pet...@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.
Cc: Ingo Molnar <mi...@redhat.com> Cc: David Vrabel <david.vra...@citrix.com> Cc: Oleg Nesterov <o...@redhat.com> Cc: Scott J Norton <scott.nor...@hp.com> Cc: Paolo Bonzini <paolo.bonz...@gmail.com> Cc: Douglas Hatch <doug.ha...@hp.com> Cc: Konrad Rzeszutek Wilk <konrad.w...@oracle.com> Cc: Boris Ostrovsky <boris.ostrov...@oracle.com> Cc: "Paul E. McKenney" <paul...@linux.vnet.ibm.com> Cc: Linus Torvalds <torva...@linux-foundation.org> Cc: Thomas Gleixner <t...@linutronix.de> Cc: "H. Peter Anvin" <h...@zytor.com> Cc: Rik van Riel <r...@redhat.com> Cc: Raghavendra K T <raghavendra...@linux.vnet.ibm.com> Signed-off-by: Waiman Long <waiman.l...@hp.com> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org> Link: http://lkml.kernel.org/r/1421784755-21945-8-git-send-email-waiman.l...@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(+) --- 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 queue_spin_unlock queue_spin_unlock @@ -15,6 +16,19 @@ static inline void queue_spin_unlock(str smp_store_release((u8 *)lock, 0); } +#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 */ --- a/include/asm-generic/qspinlock.h +++ b/include/asm-generic/qspinlock.h @@ -111,6 +111,13 @@ static inline void queue_spin_unlock_wai cpu_relax(); } +#ifndef virt_queue_spin_lock +static __always_inline bool virt_queue_spin_lock(struct qspinlock *lock) +{ + return false; +} +#endif + /* * Initializier */ --- a/kernel/locking/qspinlock.c +++ b/kernel/locking/qspinlock.c @@ -259,6 +259,9 @@ void queue_spin_lock_slowpath(struct qsp 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 * _______________________________________________ Xen-devel mailing list Xen-devel@lists.xen.org http://lists.xen.org/xen-devel
